Sound Design at Edinburgh Napier University

Category: Psychoacoustics

  • How Much Sound Does a Game Really Need? Gaetan Troutet on Casual Games, Creative Restraint, and Designing for the Real World

    Gaetan Troutet

    How much sound does a game really need?

    Most players never notice the sounds that have been deliberately left out of a game. During his online guest lecture for Edinburgh Napier University, Gaetan Troutet suggested that this is often the hallmark of successful sound design. Creating an effective soundtrack is rarely about filling every moment with audio. It is about deciding what genuinely deserves to be heard. Drawing upon his work developing casual games for Global Eagle Entertainment, he demonstrated how technical limitations, player behaviour and careful editorial judgement shape almost every creative decision. A single principle underpinned the discussion. Successful sound design depends as much upon restraint as invention.

    The environment in which Troutet’s games are played makes these decisions particularly demanding. Unlike many commercial titles developed for dedicated gaming hardware, his work must function across a diverse collection of in-flight entertainment systems installed on aircraft across the world. Some platforms provide comparatively modern hardware with generous storage and processing resources. Others continue to rely upon considerably older systems whose limited memory and bandwidth require soundtracks to be simplified before they can be deployed. The same game may therefore exist in several different technical versions, each shaped by the capabilities of the hardware on which it will eventually run. Even then, the hardware represents only part of the challenge. Every passenger experiences the soundtrack differently. Some use the headphones supplied by the airline, others connect their own, while many later encounter the same games on mobile devices with entirely different loudspeakers. Unlike a cinema or recording studio, there is no single reference listening environment. Troutet suggested that professional sound designers should accept this uncertainty rather than attempting to eliminate it. The objective is not to produce a soundtrack that sounds perfect under ideal conditions. It is to create one that continues to communicate effectively wherever it is heard.

    Although the lecture centred upon casual games, the questions Troutet raised apply to sound design far more generally. Every project exists within practical constraints, whether they involve memory budgets, processing power, production schedules or playback systems. Rather than viewing these restrictions as obstacles to creativity, Troutet argued that they often encourage clearer thinking. Once every sound occupies valuable storage, competes for the listener’s attention and requires implementation within a functioning game, designers become far more selective about what truly matters. Working as the sole audio practitioner within his development team reinforces that perspective. Troutet moves continually between creating sound effects, composing music, recording dialogue, implementing assets and collaborating with programmers and designers. Rather than treating these activities as separate disciplines, he presented them as interconnected parts of a single design process. Creative decisions influence implementation, technical limitations shape artistic choices and production realities affect every stage of development. Sound design therefore becomes inseparable from the wider process of building the game itself.

    One of the most thought-provoking moments in the lecture centred upon what appears to be a deceptively simple question. When a player performs an action, should that action always produce a sound? Many beginning designers instinctively answer yes. Buttons receive clicks. Menus receive confirmation tones. Every movement, selection, reward and transition appears to justify another layer of feedback. Troutet challenged this assumption directly. Rather than asking which sounds could be added, he encouraged students to ask which sounds genuinely improved the experience. Every additional sound competes for the listener’s attention. Every new cue alters the perceived importance of those surrounding it. Audio that initially appears informative can rapidly become repetitive, distracting or simply exhausting when heard hundreds of times during repeated play. Casual games make this question particularly important. Players often return to them repeatedly in relatively short sessions. Sounds that seem satisfying during the first few minutes may become irritating after dozens of repetitions. Troutet therefore described restraint as an active design decision rather than the absence of creativity. Silence is not an empty space waiting to be filled. It forms part of the overall balance of the soundtrack. Choosing not to add a sound may ultimately improve clarity far more than creating another effect.

    These same principles become particularly apparent in interface design, where audio functions less as decoration than as communication. Troutet encouraged students to think of interface sounds as messages directed towards the player rather than ornamental additions to menus and buttons. A confirmation tone, warning signal or navigation sound should communicate its purpose immediately, allowing players to understand what has happened without continually consulting the screen. One particularly memorable suggestion involved imagining the interface without any graphics at all. If a player were blindfolded and heard only the sounds, could they still distinguish success from failure, confirmation from cancellation, or navigation from selection? If the answer is yes, then the sounds are performing a genuine communicative role. If not, making them louder or more elaborate is unlikely to solve the underlying problem. Rather than treating interface sounds as decorative clicks or beeps, Troutet encouraged students to think of them almost as a spoken language. Every sound should communicate intention. Players should recognise whether an action has succeeded, failed or requires further input without consciously analysing what they have heard. Well-designed interface audio reduces cognitive effort. The player understands first and reflects afterwards. In this sense, interface sounds become part of the conversation between the game and the player rather than simply another layer of feedback.

    The same philosophy shaped Troutet’s approach to creating collections of related sounds. Rather than treating every effect as an independent recording selected from unrelated libraries, he described building what he called families of sounds. Interface elements, gameplay feedback and recurring actions share common characteristics, creating a recognisable sonic vocabulary throughout the game. Individual sounds may differ substantially in pitch, duration or function, though they continue to feel as though they belong together. Players may never consciously analyse these relationships, yet they often perceive the overall soundtrack as more coherent and easier to understand. Creating these relationships frequently meant recording original material rather than relying exclusively upon commercial sound libraries. Library recordings remain valuable resources, though bespoke recordings provide greater flexibility when developing a consistent sonic identity. Variations can be created from common source material, preserving subtle similarities that would be difficult to achieve using unrelated recordings gathered from multiple collections. The objective is not originality for its own sake. It is to ensure that every sound contributes towards a coherent listening experience rather than drawing attention to itself as an isolated event.

    Troutet consistently returned to the relationship between player experience and design judgement. Recording equipment, software and implementation techniques remained important, though they were never presented as ends in themselves. Every technical decision ultimately served the same objective: helping players understand, navigate and enjoy the game. Sound design therefore became an exercise in editorial judgement rather than accumulation. The important question was no longer how another sound might be added, but whether that moment genuinely deserved sound at all. Once that decision becomes the starting point, implementation, iteration and refinement begin to look rather different, forming the focus of the remainder of the lecture.

    Implementation forms the natural continuation of Troutet’s argument. Once the decision has been made that a sound genuinely deserves to exist, another set of questions immediately follows. When should it play? Under what conditions should it remain silent? How should it respond when players behave in unexpected ways? Troutet encouraged students to recognise that creating an individual sound is only one stage of the design process. A carefully recorded asset can still fail if it appears at the wrong moment, masks more important information or becomes repetitive through excessive triggering. Implementation therefore becomes an extension of sound design rather than a separate technical activity. Decisions about timing, variation and behaviour shape the player’s experience just as profoundly as the recordings themselves. Very few sounds remain unchanged after their first implementation. Once assets begin interacting with graphics, gameplay and player behaviour, weaknesses quickly become apparent. Sounds that worked well in isolation may feel intrusive within the finished game. Others disappear beneath music or gameplay effects, while some simply occur too frequently. Rather than treating these discoveries as failures, Troutet presented them as an expected part of development. Every implementation reveals more about how players actually experience the game, allowing successive revisions to refine the soundtrack until it supports interaction naturally.

    This willingness to revise also requires a particular creative mindset. Troutet observed that sound designers often invest considerable effort in creating individual recordings, making it tempting to defend them once they have been completed. Professional practice frequently demands the opposite approach. If a sound distracts players, interrupts the pacing of the game or simply fails to communicate effectively, attachment to the recording itself becomes irrelevant. During the lecture he summarised this philosophy with a familiar expression from creative practice: kill your babies. The phrase may sound severe, though the principle behind it is straightforward. The success of the overall experience matters more than preserving individual ideas. Removing or replacing a favourite sound is sometimes the decision that allows the remainder of the soundtrack to function more effectively. The willingness to edit critically therefore becomes every bit as important as the ability to create new material.

    The same philosophy extends beyond individual recordings into collaboration with the wider development team. Troutet repeatedly emphasised that sound design does not develop independently from programming, art or game design. Audio practitioners inherit decisions made elsewhere while simultaneously influencing the work of others. Effective collaboration therefore depends upon communicating design decisions in terms of the player’s experience rather than purely technical language. Requests for additional implementation features, changes to interface behaviour or modifications to gameplay become far easier to justify when they are framed around what players will understand, notice or enjoy. Communication, in this sense, becomes another aspect of sound design rather than an administrative task surrounding it. Professional organisation supports that collaboration in equally practical ways. Clear file names, consistent project structures and carefully maintained asset libraries rarely receive the same attention as recording or mixing, yet they influence every subsequent stage of production. Projects evolve over months or years, assets require continual revision and other members of the team must be able to locate the correct material quickly. Well organised sessions reduce confusion, simplify implementation and ultimately create more opportunities for genuinely creative work.

    Troutet also cautioned against becoming overly attached to particular software, plug-ins or recording equipment. Digital audio workstations continue to evolve, new tools appear regularly and production techniques inevitably change across a career. These developments undoubtedly influence professional practice, though they remain only means of achieving a larger objective. The more important questions concern what the player should hear, what information deserves emphasis and how audio contributes to the overall experience of the game. The same perspective shaped his comments on sources of inspiration. Commercial sound libraries, films and existing games all provide valuable references, though they should never replace careful design thinking. A distinctive soundtrack emerges through the relationships between sounds, the pacing of interaction and a clear understanding of the audience rather than through the novelty of any individual recording. Troutet consistently returned to the idea that sound design is fundamentally a process of making informed decisions rather than collecting techniques.

    Troutet repeatedly argued that sound should guide interaction rather than compete with it. Audio may reward success, reinforce important actions or draw attention towards changing events, though it should rarely distract players from the activity itself. This philosophy connects directly to the earlier discussions of restraint, interface communication and coherent families of sounds. Every element of the soundtrack exists to support understanding. Once a sound begins attracting attention to itself rather than to the player’s experience, its purpose deserves to be questioned. The measure of successful sound design is therefore not how much audio has been added to a game, but whether every element continues to justify its presence through the experience it creates for the player.

    The lecture concluded by returning, implicitly, to the same deceptively simple question that had shaped the discussion from the beginning. How much sound does a game really need? Troutet offered no universal formula. Different genres, audiences and platforms inevitably require different solutions. Instead, he encouraged students to replace assumptions with judgement. Does this sound communicate something important? Does it improve the player’s understanding? Does it strengthen the overall experience? If the answer is no, then adding more audio is unlikely to solve the problem. Careful omission often represents a stronger design decision than continual addition. Across examples ranging from airline entertainment systems to interface design, implementation and professional collaboration, Troutet consistently presented sound design as an exercise in thoughtful selection. The defining characteristic is judgement. Choosing which sounds deserve to exist, how they relate to one another and when they should remain silent requires an understanding of perception, interaction and communication that extends far beyond recording individual effects. Successful sound design is therefore measured not by the quantity of sounds within a project, but by how effectively those sounds help players understand, navigate and enjoy the worlds they inhabit.

  • How Do You Design Great Sound for Terrible Speakers? Tracy Bush on Creative Constraints, Game Audio, and Designing for the Real World

    Tracy Bush

    How do you design great sound for terrible speakers?

    Modern games present players with remarkably convincing sonic worlds. Dialogue responds naturally to changing situations, environments feel alive with movement and atmosphere, interfaces communicate information almost instinctively, and music adapts to the pace of play. Looking at contemporary productions, it is easy to imagine that these achievements are primarily the result of increasingly powerful technology. During his online guest lecture for Edinburgh Napier University, Tracy Bush suggested something rather different. Drawing upon a career that has included Blizzard Entertainment, Sony Online Entertainment, NCSoft and Sphero, he described how some of the most effective sound design emerges when technology imposes severe limitations. Small memories, limited processors, unpredictable playback systems and tiny loudspeakers do not simply restrict creativity. They force designers to think more carefully about what listeners genuinely need to hear.

    Bush’s own career reflected the rapid evolution of the games industry itself. Music had always formed an important part of his life, though his professional background began in information technology rather than audio. While working during the day, he spent evenings performing as a pianist in bars around San Francisco. After relocating to southern California, he joined Blizzard Entertainment in an IT role. His musical interests gradually became known throughout the company, leading colleagues to involve him in audio work whenever opportunities arose. Rather than following a carefully planned route into game sound, his career developed through a willingness to solve unfamiliar problems wherever they appeared. Looking back, Bush suggested that many people entered the industry in much the same way. Studios were small, responsibilities overlapped, and individuals frequently discovered new specialisms simply by becoming the person willing to tackle the next challenge.

    The games industry of the late 1990s differed substantially from the one students encounter today. Development teams were comparatively small, production pipelines remained fluid and many working practices were still evolving. Audio departments often worked alongside programmers, artists and designers in highly collaborative environments where formal boundaries between disciplines were less rigid than they later became. Bush described an atmosphere in which experimentation emerged naturally from everyday work. New hardware appeared rapidly, production tools changed continuously and every project seemed to introduce another set of technical problems that required fresh solutions. Experience remained valuable, though it rarely eliminated uncertainty.

    The computers on which players experienced those games introduced another level of unpredictability. Audio hardware varied enormously between systems, making consistent playback almost impossible to guarantee. Different sound cards reproduced music in noticeably different ways, while MIDI playback depended heavily upon whichever synthesis hardware happened to be installed inside an individual computer. A carefully balanced piece of music created inside the studio might sound dramatically different once it reached somebody else’s machine. Sound designers could control what left the studio. They could not control how it would ultimately be heard.

    This uncertainty extended well beyond music. Dialogue, sound effects and ambience all passed through hardware whose behaviour remained largely outside the control of the development team. Rather than designing for one predictable playback system, audio professionals found themselves designing for thousands of possible listening environments. Bush described this as one of the defining characteristics of early game audio. The question was rarely how a soundtrack sounded under ideal conditions. Instead, designers learned to ask whether it continued to communicate effectively when reproduced by equipment they had never encountered. The playback system itself became part of the design problem.

    Although contemporary technology has advanced enormously, the underlying challenge remains surprisingly familiar. Players now experience games through televisions, headphones, laptops, handheld consoles, mobile phones and increasingly varied listening environments, each introducing its own acoustic character. Perfect consistency remains elusive. The responsibility of the sound designer therefore extends beyond producing interesting sounds. It includes anticipating how those sounds will survive the journey from the studio to the listener.

    Bush also reflected upon the rapid transformation of production tools during this period. Early editing systems offered comparatively limited support for assembling large projects, requiring significant manual organisation and making complex revisions both time-consuming and potentially destructive. The arrival of Pro Tools transformed those workflows, allowing audio teams to edit non-destructively, manage increasingly complex sessions and collaborate more effectively. At much the same time, improvements in virtual sampling gave composers access to increasingly expressive orchestral sounds without requiring every revision to involve live performers. These developments expanded what small audio teams could realistically achieve while allowing creative ideas to evolve throughout production rather than becoming fixed at an early stage.

    The tools available to sound designers evolved just as quickly. Bush described middleware as another important step in that development. As implementation systems became more sophisticated, audio teams gradually assumed greater responsibility for how sounds behaved inside games rather than simply supplying recordings for programmers to trigger. Interactive playback, transitions and behavioural logic increasingly became part of the sound designer’s creative role. Technology expanded the possibilities available to audio departments, though it also broadened their responsibilities. Understanding implementation became almost as important as creating the sounds themselves.

    One observation from Bush’s time at Blizzard challenged another common assumption about technological progress. Greater technical capability did not necessarily encourage increasingly elaborate soundtracks. He reflected upon how musical direction gradually changed across successive projects, with later productions often favouring greater restraint rather than greater complexity. Earlier scores frequently relied upon dense orchestral textures intended to create scale and spectacle. Later work often achieved stronger dramatic results through simpler arrangements that allowed individual musical ideas greater space to breathe. Rather than filling every available moment with sound, composers became increasingly selective about where music should lead the player’s attention and where silence or restraint could prove more effective.

    The same principle appeared throughout sound design more generally. Memory budgets restricted how many sounds could be stored. Processor limitations reduced the number that could play simultaneously. Dialogue budgets limited the amount of recorded speech available to designers. Every technical restriction demanded choices. Which sounds genuinely communicated useful information? Which could be simplified without affecting the player’s experience? Which details would most influence the way a moment was perceived? Bush’s examples repeatedly suggested that successful sound design depends less upon including everything that is technically possible than upon identifying what is genuinely important for the listener.

    By this stage of the lecture, the discussion had established a way of thinking that extended well beyond the technology of any particular decade. New hardware, new software and new production methods continually alter the practical challenges facing sound designers, yet they rarely change the underlying task. Every project begins with a listener, a playback system and a collection of technical constraints that cannot simply be ignored. The role of the sound designer is to understand those conditions and create the most convincing experience possible within them.

    The relationship between creativity and constraint became considerably more tangible during Bush’s work with Sphero, where many of the assumptions underlying conventional game audio no longer applied. Working on licensed products featuring characters such as R2-D2, BB-8 and Lightning McQueen involved far more than transferring familiar techniques onto a different platform. Every sound would eventually emerge from a miniature loudspeaker housed inside a compact plastic enclosure containing motors, batteries, gears and electronic components. The finished product would be heard in kitchens, classrooms, living rooms and gardens rather than through carefully positioned studio monitors or high-quality headphones. Under those conditions, many established production practices simply ceased to be useful. The question was no longer how a sound performed inside the studio. It became how that sound survived once it reached the device for which it had actually been designed.

    Bush described changing his workflow to reflect that reality. Rather than completing the sound design and then testing it on the finished hardware, he monitored much of his work directly through the loudspeaker installed inside the product itself. Equalisation, dynamics, tonal balance and overall character were judged using exactly the same hardware that customers would eventually hear. The acoustic behaviour of the enclosure, the resonances introduced by the plastic casing and even the mechanical sounds generated by the internal motors became part of the design process. Instead of treating these characteristics as defects to be corrected afterwards, they became factors that shaped creative decisions from the beginning.

    The approach illustrates an important principle that extends well beyond embedded devices. Playback systems are never neutral. Every loudspeaker, pair of headphones, television or mobile phone colours the material passing through it. Sound designers often devote considerable attention to recording, editing and mixing, though the listening environment ultimately contributes just as much to the audience’s experience. Bush repeatedly returned to the importance of understanding where sounds will actually be heard. A design that performs beautifully on large studio monitors may communicate surprisingly little through the hardware used by most listeners. Successful sound design therefore depends not only upon creating interesting sounds, but also upon understanding the conditions under which those sounds will be experienced.

    Tiny loudspeakers presented another unavoidable challenge. Their physical dimensions simply prevented them from reproducing deep bass with any real authority. Attempting to force low frequencies through such hardware produced distortion long before it created convincing weight. Rather than attempting to overcome those physical limitations directly, Bush exploited the way listeners perceive sound. By introducing carefully controlled upper harmonics, he encouraged the auditory system to infer the presence of frequencies that the loudspeaker itself could not reproduce. The hardware remained unchanged, though the listening experience became noticeably richer.

    The solution depended upon psychoacoustics rather than brute force. Human hearing does not operate as a simple measuring device. Listeners continually reconstruct incomplete information, using harmonic relationships, timing cues and previous experience to build coherent auditory impressions. Bush’s work demonstrated how understanding those perceptual processes can prove more valuable than pursuing technically impossible specifications. The objective was never to reproduce frequencies that the loudspeaker could not generate. It was to create a convincing impression of fullness using the resources that remained available. Throughout the lecture, this distinction emerged repeatedly. Good sound design often depends less upon reproducing reality perfectly than upon understanding how listeners interpret what they hear.

    Sampling rates introduced another practical compromise. Embedded devices offered only a fraction of the storage and processing power available to contemporary games, requiring careful management of bandwidth and memory. Bush explained that these restrictions became particularly noticeable when working with robotic characters such as R2-D2, whose personality depends upon bright electronic vocalisations occupying the upper regions of the frequency spectrum. Lower sampling rates inevitably reduced the highest frequencies that could be reproduced accurately, making filtering and careful spectral management essential parts of the design process. Concepts that students often encounter as digital audio theory became everyday creative decisions affecting how expressive and recognisable the finished character would become.

    The material supplied by Lucasfilm also revealed how much organisation underpins apparently effortless performances. Bush did not receive complete scenes or finished sequences ready to be inserted into the product. Instead, he worked with an extensive collection of individual R2-D2 vocalisations drawn from the films. These recordings were not simply organised according to pitch or duration. Their emotional character proved considerably more important. Expressions of curiosity, excitement, concern, frustration and amusement were grouped together so that the robot’s responses could reflect changing situations while remaining faithful to the personality audiences already recognised.

    Randomisation played an important role, though not in the simplistic sense of allowing any sound to play at any time. Bush described carefully controlled systems that introduced variation without sacrificing recognisability. Human listeners identify repeated patterns remarkably quickly, yet behaviour that appears completely unpredictable can feel equally artificial. Convincing interactive audio therefore occupies a position between repetition and randomness. Familiar vocalisations return often enough to establish character, while subtle variations prevent those repetitions from becoming mechanical. The objective is not to surprise the listener continually, but to create the impression of a responsive and expressive personality.

    The same balance appears throughout interactive sound design. Footsteps, interface sounds, environmental ambiences and weapon effects all benefit from controlled variation rather than unlimited randomness. Collections of related recordings, small differences in pitch or timing and carefully managed playback logic often produce more convincing results than vast libraries of unrelated sounds. Bush’s examples demonstrated that believable behaviour frequently depends upon the relationships between sounds rather than the number of sounds available.

    As the lecture broadened beyond embedded devices, Bush argued that creating individual sounds represents only one part of a modern sound designer’s role. Interactive media introduces challenges that simply do not exist in linear forms such as film or television. A film editor knows exactly when every line of dialogue will be heard and how every scene will unfold. Games surrender much of that control to the player. Conversations may begin unexpectedly, be interrupted, or never occur at all. Players may spend hours exploring one environment while another moves through it in minutes. The soundtrack therefore cannot be constructed as a fixed sequence of events. It has to respond continuously to changing circumstances.

    Middleware transformed this aspect of production. Earlier generations of game development relied heavily upon programmers to implement even relatively modest audio behaviour. As middleware matured, sound designers gained much greater control over how sounds responded to events within the game itself. Playback logic, transitions, priorities and interactive behaviours increasingly became part of the sound designer’s creative responsibility. Recording remained an important part of the job, though implementation became equally significant. Designing how sounds behave proved just as important as designing the sounds themselves.

    This shift also changed the relationship between audio departments and the wider development team. Bush repeatedly emphasised that sound design does not exist in isolation. Programmers determine what information becomes available. Designers establish the systems that govern player behaviour. Writers shape dialogue, animators influence timing and movement, while artists define the visual environments within which sounds operate. Audio departments respond to all of these decisions while contributing their own expertise in return. Successful interactive soundtracks emerge through continual collaboration rather than from any single discipline working independently.

    One discussion during the lecture addressed the way sound professionals are perceived within development teams. Bush reflected on labels such as “the sound guy” or “the noise boy”, expressions that dramatically underestimate the breadth of contemporary audio practice. Modern sound designers contribute far beyond the creation of individual sound effects. They solve technical problems, shape interactive behaviour, collaborate across disciplines and influence how players ultimately experience the game. Titles such as Audio Director acknowledge that broader creative and technical responsibility.

    Questions from students later turned towards virtual reality, where many of these relationships become even more apparent. Convincing virtual environments depend upon much more than visual realism. Sound provides continuous information about distance, movement, scale and spatial relationships, allowing users to build coherent mental models of spaces extending beyond their immediate field of view. Carefully designed spatial audio therefore contributes directly to presence, orientation and immersion rather than acting as a decorative addition to the visual experience.

    Across subjects as varied as desktop games, embedded devices, robotic toys and virtual reality, Bush repeatedly returned to the same way of thinking. Every project began with an understanding of the available technology, the listening conditions and the perceptual abilities of the audience. The hardware changed dramatically throughout his career, though the questions facing the sound designer remained remarkably consistent. Rather than asking how to exploit every available technical capability, Bush continually asked what listeners actually needed to hear and how the available technology could communicate that experience most effectively.

    Across projects as different as Blizzard’s games, Sphero’s robotic products and emerging virtual reality systems, Bush consistently returned to the same set of design questions. Technology continued to change throughout his career, introducing new platforms, workflows and constraints, yet the underlying task remained remarkably stable. Successful sound design depended upon understanding how people listen, how technology behaves and how creative decisions bridge the gap between the two. Whether working with a full orchestral score, an interactive dialogue system or a miniature loudspeaker inside a robotic toy, the objective was never simply to produce impressive sounds. It was to create listening experiences that remained convincing under the conditions in which they would actually be heard.

  • How Do We Know What We Are Hearing? Professor Albert S. Bregman on Auditory Scene Analysis and Perceptual Organisation

    Albert Bregman

    How do we know what we are hearing?

    The question sounds simpler than it is. A voice is heard as a voice. A violin is heard as a violin. A passing vehicle is recognised almost immediately. Everyday listening creates the impression that sound sources reveal themselves directly. Most people rarely stop to consider how much processing has already taken place before recognition becomes possible. Professor Albert S. Bregman’s research begins from the observation that sound sources do not arrive at the ears. Acoustic mixtures do. By the time vibrations reach a listener, contributions from many different events have already combined. Voices, musical instruments, footsteps, ventilation systems, birdsong, machinery, and countless other sources may all contribute to the same signal. The auditory system must somehow determine which parts of that mixture belong together and which do not. Before Bregman’s work, hearing research had developed detailed accounts of pitch, loudness, masking, localisation, and frequency analysis. Considerably less attention had been paid to a more fundamental question. How does a listener determine what produced a sound?

    Bregman did not begin with a theory. He began with a puzzle. During memory experiments involving sequences of short sounds, he noticed that listeners often perceived groupings that were not physically present within the stimulus itself. Sounds sharing similar characteristics appeared to organise themselves into separate perceptual streams. The observation recalled ideas from Gestalt psychology, where visual elements combine into structures that cannot be understood simply by examining their individual parts. What began as an unexpected observation gradually became a larger problem. If listeners organise sounds into streams, how does that organisation occur? More importantly, what role does it play in perception itself? Bregman often approached the issue through analogy. Imagine standing beside a lake while observing only two floating markers moving up and down on the water’s surface. The movement provides evidence that something has happened, though many explanations remain possible. A boat may have passed nearby. Several boats may be moving in different directions. Wind may be disturbing the surface. Something may have fallen into the water. The available evidence does not identify the cause. Any conclusion depends upon inference. According to Bregman, hearing presents a similar challenge. The ears receive information about acoustic activity, though they do not receive direct information about the events that produced it. From patterns of pressure variation reaching two eardrums, listeners somehow infer the existence of voices, instruments, machines, animals, and other sound-producing events. Nothing in the signal arrives labelled. The auditory system must determine which acoustic components belong to the same source.

    Questions of speech perception, localisation, attention, and communication all depend upon this process. Before speech can be understood, before a melody can be followed, and before a sound source can be identified, the auditory system must first determine which acoustic components belong together. Organisation is therefore not one stage among many. It provides the conditions under which many other aspects of perception become possible. This perspective led Bregman towards what became known as auditory scene analysis. The term reflects an analogy with vision. Just as visual perception involves identifying objects within a visual scene, auditory perception involves identifying sound-producing events within an acoustic scene. The challenge lies in the fact that sound sources combine before reaching the listener. The auditory system therefore faces a decomposition problem. It must separate a complex mixture into components that plausibly belong to distinct events. A central claim running throughout the lecture was that perception involves more than detecting acoustic information. It also involves organising that information. Bregman’s demonstrations repeatedly returned to this point. Listeners often assume that qualities such as rhythm, melody, pitch, loudness, timbre, and location belong directly to sounds themselves. His examples suggested a more complicated picture.

    Auditory stream segregation provides one illustration. Under certain conditions, listeners stop hearing a single sequence of sounds and begin hearing multiple independent streams. Once this occurs, rhythms that were previously obvious may disappear. New rhythmic structures emerge. Melodic patterns change. The acoustic signal remains unchanged, though the perceptual outcome does not. Bregman’s demonstrations suggested that the consequences extend much further than rhythm or melody alone. Again and again, he returned to the idea that many perceptual properties depend upon how sounds are grouped. Listeners often assume that pitch, loudness, timbre, and spatial location belong directly to sounds themselves. Yet these properties can also be influenced by the way acoustic components are assembled into perceptual objects. When those groupings change, perception may change even when the underlying stimulus remains constant. This claim sits near the centre of auditory scene analysis. The framework is not simply concerned with separating one sound source from another. It is concerned with how perceptual objects are formed in the first place. Before listeners can judge the loudness of a sound, identify its pitch, recognise its timbre, or determine its location, the auditory system must first decide which components belong together. The resulting structure shapes many of the properties that listeners subsequently experience. From this perspective, perception becomes a problem of interpretation. Faced with an acoustic mixture, the auditory system must determine which explanation is most plausible. What listeners hear is not a direct copy of the physical world. It is the outcome of a process through which the auditory system attempts to reconstruct the events most likely to have produced the available evidence.

    Bregman argued that listeners exploit regularities commonly found in the physical world. Certain acoustic relationships provide evidence that components are likely to originate from the same source. Harmonicity offers one example. Many naturally occurring sounds contain frequency components related by simple numerical ratios. When such relationships are detected, the auditory system often groups those components together. Similar reasoning underlies what Bregman described as common fate. Components that begin together, change together, or move together over time frequently appear to belong to the same event. These principles do not guarantee correct interpretation. Rather, they provide strategies that usually correspond with the structure of the physical world. Auditory scene analysis is therefore concerned with probability rather than certainty. The auditory system rarely knows exactly what caused a sound. It generates interpretations that are likely to account for the available evidence. Most of the time those interpretations correspond closely enough to events in the environment that listeners remain unaware that any interpretation has occurred at all. Throughout the lecture, Bregman emphasised that these organisational processes usually pass unnoticed. Listeners rarely experience themselves as constructing interpretations. The world appears already divided into voices, instruments, footsteps, vehicles, and other familiar sources. Auditory scene analysis directs attention to the work required to produce that impression. The apparent simplicity of hearing may be one reason the problem remained difficult to recognise. Successful perception conceals many of the processes that make it possible.

    Music occupied an interesting position within the lecture. Bregman suggested that composers had discovered practical consequences of auditory organisation long before psychologists attempted to explain them. Counterpoint, orchestration, and performance practice frequently involve maintaining distinctions between perceptual streams or encouraging sounds to fuse into larger structures. Musical traditions therefore provide a long record of experimentation with the same organisational tendencies that auditory scene analysis later sought to describe. Music also offers situations in which these processes become unusually apparent. Changes in perceptual organisation can alter the melodies and rhythms listeners hear, making it possible to observe principles that often remain hidden during everyday listening. Bregman was not suggesting that composers were unconsciously applying psychological theory. Rather, centuries of musical practice had encountered many of the same perceptual constraints that later became objects of scientific investigation.

    Yet music represented only one instance of a broader phenomenon. Following a conversation in a crowded room, recognising a familiar voice over the telephone, locating a sound source in a busy environment, distinguishing one instrument from another, and understanding speech in noise may appear to involve different problems. Bregman’s framework suggested that each depends upon a prior act of organisation. Auditory scene analysis altered the relationship between many areas of hearing research by drawing attention to this common foundation. Rather than treating speech, music, localisation, and auditory attention as entirely separate domains, the framework highlighted organisational processes upon which they all depend. Seen in this way, auditory scene analysis is not merely a theory about particular auditory illusions or laboratory demonstrations. It addresses a question that sits beneath much of auditory perception research. How does a listener move from an undifferentiated acoustic mixture to a world populated by distinct events, objects, and sources?

    The framework also shifted attention away from sound as a purely physical phenomenon and towards perception as a process of inference. Earlier approaches often focused on the contents of the acoustic signal. Bregman drew attention to a prior question. Before a listener can recognise a voice, identify an instrument, understand speech, or respond to a warning signal, the auditory system must first decide what probably caused the sound.

    The answer is usually reached so quickly that the problem remains unnoticed. Voices appear as voices. Instruments appear as instruments. Bregman’s work suggests otherwise. Listening depends upon a continual process through which the auditory system constructs explanations from incomplete evidence. Most of the time those explanations correspond closely enough to the surrounding environment that hearing feels direct and effortless.

  • Can Sound Quality Be Measured? David Bowen on Psychoacoustics, Product Design, and Human Perception

    David Bowen

    Can sound quality be measured?

    For engineers, the question seems perfectly reasonable. Modern acoustic analysis can measure sound pressure levels, frequency content, vibration, loudness, roughness, sharpness, tonal components, and countless other characteristics. Faced with such an abundance of data, it is tempting to assume that product sound quality can ultimately be reduced to a collection of numbers. If we can measure a sound accurately enough, surely we can determine whether it is good or bad.

    During his online guest lecture for Edinburgh Napier University, David Bowen spent much of his time explaining why the answer is not nearly so simple. Across more than three decades working in acoustics, vibration, psychoacoustics, and product sound quality, Bowen has helped organisations understand how people respond to the sounds products make. Throughout a career spanning industrial research, consultancy, and product development, he has worked at the intersection of acoustics, psychoacoustics, engineering, and product design. Again and again, his examples pointed towards the same conclusion. Sound can be measured. Sound quality cannot.

    This distinction formed the foundation of the lecture. Sound quality, Bowen argued, is not a property of a product. It is a response of people. A microphone does not experience annoyance. A sound level meter does not perceive quality. Only listeners do. Understanding product sound quality therefore requires understanding both the physical sound and the human beings who hear it. Difficulties emerge as soon as engineers attempt to connect measurements to human responses. Bowen illustrated this challenge through examples in which sounds with similar measured levels produced dramatically different subjective reactions. A pure tone, broadband noise, an organ note, or a piece of industrial machinery may all produce similar sound levels, yet listeners often describe them in very different ways. Some sounds are judged pleasant. Others are irritating. Some feel powerful. Others feel weak. Part of the difficulty lies in the way human hearing operates. Psychoacoustics has demonstrated repeatedly that listeners do not experience sound in a simple or linear fashion. Sensitivity varies across frequencies. Loudness does not increase proportionally with sound pressure. Perception depends not only upon what reaches the ears but also upon how the brain interprets it. Measuring the sound itself is only part of the problem.

    Bowen illustrated this point through several examples that challenge common assumptions about listening. Human memory for loudness is surprisingly limited. When listeners hear two sounds separated by even a relatively short interval, their ability to compare levels accurately begins to deteriorate. Judgements become influenced by expectation, context, and interpretation rather than purely acoustic characteristics. Even when measurements are reliable, the perceptual processes through which listeners experience those sounds remain considerably more complex.

    For decades, researchers attempted to bridge this gap through increasingly sophisticated metrics. If sound pressure level proved insufficient, perhaps loudness would provide a better predictor. If loudness proved inadequate, perhaps perceived noisiness, roughness, sharpness, or other psychoacoustic measures would help. Each new metric offered valuable insights, yet each also revealed new limitations. Bowen discussed how the arrival of jet aircraft exposed weaknesses in existing approaches to noise evaluation, prompting the development of measures intended to capture perceived noisiness more effectively. Those measures improved predictions in some contexts while proving less successful in others. Similar challenges emerged across industrial machinery, transportation systems, and consumer products. As soon as one perceptual factor appeared understood, another emerged. Listening proved stubbornly resistant to simple description.

    Bowen’s career spans a period during which acoustics increasingly recognised that physical measurements alone could not explain human responses. Successive generations of psychoacoustic metrics attempted to narrow the gap between measurable sound and perceived quality. Each represented an improvement upon what came before, though none provided a complete solution. Human perception remained influenced by context, expectation, memory, meaning, and experience. The history of product sound quality therefore became, in part, a history of increasingly sophisticated attempts to understand how people listen. Similar problems emerge elsewhere. A piano recording played backwards retains many of its measurable characteristics, yet listeners immediately perceive something fundamentally different. What sounds like a piano becomes something closer to an organ. Human listeners detect meaningful changes that conventional measurements often struggle to explain. Again and again, perception proves more complicated than measurement.

    If measurements alone cannot fully predict how people will respond, a difficult question follows. How should products be designed?

    For Bowen, the answer lies in listening. Much of the lecture focused on sound quality jury testing, a methodology that places human listeners at the centre of the evaluation process. Rather than asking which sound measures best, researchers ask which sound people prefer, which sound communicates particular qualities, and which sound supports the intended experience of a product.

    This creates an interesting tension. Engineers naturally seek measurements. Manufacturers want targets that can be specified, monitored, and improved. Product development processes favour quantities that can be compared and optimised. Yet listeners remain the ultimate judges of quality. No matter how sophisticated a measurement becomes, a product succeeds or fails according to how people experience it. Jury testing therefore emerged not as a rejection of engineering but as a recognition that engineering alone could not answer every question.

    Carefully designed listening tests provide information that measurements alone cannot. This approach complements rather than replaces traditional acoustic analysis. Measurements help researchers understand what a product is doing acoustically. Listening tests help them understand how people respond. Product sound quality emerges through the relationship between these two perspectives. Designing listening tests of this kind is far from straightforward. Participants must be selected carefully. Stimuli need to be prepared consistently. Presentation order can influence responses. Questions must be designed in ways that avoid leading participants towards particular conclusions. Statistical analysis becomes essential if meaningful patterns are to emerge from the resulting data. Throughout the lecture, Bowen emphasised that listening tests require as much methodological care as any engineering measurement.

    One particularly interesting aspect of this work involves the creation of what Bowen described as virtual products. Rather than constructing numerous physical prototypes, researchers can isolate individual sound components and manipulate them independently. Motor noise, airflow noise, pump sounds, valve sounds, and other elements can be adjusted before being recombined into new versions of the product. Listeners can then evaluate these alternatives, allowing researchers to explore how specific design decisions influence perceived quality without repeatedly redesigning the product itself.

    One of the lecture’s most illuminating examples involved front-loading washing machines. Modern washing machines generate a wide range of sounds, including motor noise, water movement, pumping systems, valves, and the movement of clothes within the drum. Traditional noise control might focus simply on reducing these sounds wherever possible. Bowen’s research adopted a different approach. Rather than treating the machine as a single noise source, the different sounds produced during filling, washing, draining, and spinning were analysed separately. Each stage introduced its own acoustic characteristics and potential design challenges. Water movement, pump operation, motor behaviour, valve activity, and the interaction between clothes and the drum all contributed differently to listener perceptions. Individual sound components were isolated and manipulated. Participants evaluated these variations through listening tests, allowing researchers to identify which sounds influenced acceptability most strongly.

    The resulting data could then be analysed using statistical models that linked changes in specific sound components to listener ratings. One of the most interesting aspects of this work involved the creation of response-surface models that allowed engineers to visualise how perceived quality changed as different sound characteristics were adjusted. Rather than producing a simple pass-or-fail result, the models created maps of possible design outcomes. Engineers could explore how increasing one characteristic while reducing another might influence listener responses. Product sound quality rarely involves finding a single perfect solution. Designers must balance acoustic quality against manufacturing constraints, performance requirements, reliability considerations, and cost limitations. Statistical modelling provides a way of navigating these trade-offs while retaining a clear understanding of how design decisions influence perception.

    Similar principles appeared in Bowen’s work on vacuum cleaners. Consumers often claim that they want quieter products, yet a vacuum cleaner that becomes almost silent introduces a different problem. Users may begin to question whether it is working properly. Certain sounds communicate power, airflow, and cleaning effectiveness. Eliminating every sound is not necessarily desirable. In this case, the challenge is not simply reducing noise but preserving those aspects of the sound that contribute positively to the user’s perception of performance. What emerges from Bowen’s examples is a view of product sound that differs significantly from traditional approaches to noise control. Sounds are not merely by-products of mechanical systems. They communicate information about performance, condition, reliability, quality, and identity. A washing machine, a vacuum cleaner, a refrigerator, and an aircraft each occupy different places in people’s lives. Listeners bring different expectations to each. A refrigerator should not sound like a lawnmower. Equally, a lawnmower should not sound like a refrigerator. The challenge is therefore not simply reducing sound, but designing sounds that make sense within a particular context.

    Seen in this light, product sound quality becomes a remarkably human problem. Engineers can measure sound with extraordinary precision. Researchers can develop increasingly sophisticated psychoacoustic models. Statistical techniques can reveal relationships between acoustic characteristics and listener preferences. Yet none of these tools removes the need to understand people. Sound quality emerges not from products alone but from the relationship between products and listeners. What emerged from the lecture was a challenge to a familiar engineering instinct. Faced with a difficult problem, engineers naturally seek better measurements. Bowen’s work suggests that measurements remain essential, though they are not enough on their own. Product sound quality exists at the point where physical acoustics meets human perception. This creates an unusual situation. Few areas of engineering depend so heavily upon subjective judgement while simultaneously demanding rigorous measurement. Product sound quality requires microphones, analysers, statistical models, listening tests, psychoacoustic theory, and human listeners. Remove any one of these elements and the picture becomes incomplete.

    Perhaps this is why the question that opened the lecture remains so difficult to answer. Can sound quality be measured? David Bowen’s career suggests that the answer is both yes and no. Sounds can be measured with extraordinary precision. Human responses can be studied, modelled, and predicted. Yet quality itself ultimately emerges through experience. The most successful products are not necessarily the quietest products, nor the products with the best acoustic measurements. They are the products whose sounds make sense to the people who use them. In the end, product sound quality is not really about sound at all. It is about understanding listeners.

  • Who Are We Designing For? Professor Bruce Walker on Sound, Accessibility, and Human-Centred Design

    Bruce Walker

    Who are we designing for?

    At first glance, the answer appears obvious. Designers create products for users. Engineers build systems to help people accomplish tasks. Technology exists to solve problems. Yet during his online guest lecture for Edinburgh Napier University, Professor Bruce Walker repeatedly returned to examples suggesting that the answer is often more complicated than it first appears. Again and again, he described situations in which technically impressive systems failed to account for the realities of the people expected to use them. A solution might work perfectly according to engineering specifications while proving frustrating, distracting, or simply undesirable in practice. Across projects involving navigation, education, museums, accessibility, sonification, and auditory interfaces, Walker argued that successful design begins not with technology but with understanding human needs.

    Sound provided the central thread running through the lecture. Many people associate auditory interfaces with simple alerts and alarms. Computers beep. Phones ring. Vehicles issue warning tones. Yet Walker demonstrated that sound can serve far more sophisticated purposes. It can guide navigation, communicate data, support education, enable accessibility, assist decision-making, and provide entirely new ways of interacting with technology. These possibilities emerge not from adding sounds indiscriminately but from carefully considering what information people need, when they need it, and how they can use it effectively.

    This emphasis on understanding users before designing solutions appeared throughout the lecture. These broader questions became particularly visible in Walker’s discussion of the SWAN project, the System for Wearable Audio Navigation. The goal was deceptively simple. Could sound help people navigate when they could not rely on vision? Blind users are an obvious example, though Walker deliberately framed the problem more broadly. Firefighters moving through smoke-filled buildings, soldiers operating at night, divers underwater, and workers engaged in visually demanding tasks may all find themselves unable to look or unable to see. Rather than designing exclusively for a particular group, the project focused on a shared perceptual challenge.

    Approaching the problem in this way immediately changed the nature of the design process. Navigation might seem like a familiar activity, something most people perform every day without conscious thought. Yet once the team began analysing the task carefully, they discovered layers of complexity hidden beneath the surface. People need to know where to go, though they also need information about obstacles, changes in terrain, landmarks, hazards, and points of interest. Navigation is not simply a matter of moving from one location to another. It involves understanding an environment while continuously making decisions within it.

    The resulting system employed spatialised audio beacons that users could follow through space. Walker compared them to a virtual carrot suspended ahead of the listener. Rather than receiving a sequence of verbal instructions, users simply moved towards a sound source. When a turn became necessary, the sound shifted position accordingly. The concept appears elegant partly because it exploits abilities listeners already possess. Humans are remarkably good at locating sounds. Rather than teaching an entirely new interaction technique, the system builds upon existing perceptual skills.

    What makes the project particularly revealing, however, is the extent to which users shaped its development. Early assumptions frequently proved incorrect. Designers initially believed they should describe surface transitions in detail, informing users when they were moving from pavement to grass or from one surface to another. Users quickly pointed out that such information was often redundant. They already knew where they were standing. What mattered was knowing what was coming next. By listening carefully to users rather than insisting upon their original assumptions, the team produced a more efficient and less intrusive system.

    This pattern appeared repeatedly throughout the lecture. Successful auditory interfaces emerge through collaboration, observation, and evaluation rather than through technological enthusiasm alone. Walker repeatedly emphasised the importance of testing systems with real users performing real tasks. Maps of navigation paths, performance data, error rates, and subjective feedback all played important roles in understanding whether a design genuinely worked. The question was never whether a system could be built. The question was whether it improved people’s ability to accomplish what they were trying to do.

    Perhaps nowhere was this philosophy more apparent than in the team’s work with bone-conduction audio. Navigation systems often rely upon stereo or spatial audio, which typically requires headphones. Yet many users rejected conventional headphones immediately. Blind people rely heavily upon environmental sounds. Firefighters need to hear what is happening around them. Covering the ears solved one problem while creating another. Rather than treating this as an unavoidable limitation, the researchers reconsidered the entire system. Bone-conduction devices allowed spatial audio to be delivered without blocking environmental awareness. Once again, the solution emerged not from pursuing technology for its own sake but from understanding the realities of users’ lives.

    Walker extended these ideas beyond navigation into the design of auditory menus and interfaces. Modern computer systems contain large amounts of information organised visually through menus, icons, scroll bars, and navigation structures. Translating these elements into sound presents significant challenges. Simply reading everything aloud through text-to-speech quickly becomes inefficient and frustrating. Long contact lists, extensive music libraries, and complex software systems require more sophisticated approaches.

    Many of the solutions developed by Walker and his collaborators demonstrate an intriguing combination of technical ingenuity and psychological insight. Spearcons, for example, compress spoken words into highly abbreviated auditory cues that users rapidly learn to recognise. Spindex systems provide indexing sounds that help listeners move efficiently through large collections without hearing every item in sequence. Whispered speech can indicate unavailable menu items while preserving the overall structure of an interface. These innovations are clever, though their importance lies less in their novelty than in their effectiveness. Each emerged through extensive experimentation designed to determine what users actually understood and preferred. What makes this work particularly interesting is that it was never simply about making visual interfaces audible. Instead, it explored how auditory interfaces might exploit the strengths of listening itself. Users do not experience sound in the same way they experience vision, and successful interfaces acknowledge that difference rather than treating audio as a substitute for a screen.

    The lecture repeatedly highlighted a distinction between engineering and design. Engineering can produce systems that function correctly. Design concerns whether people will actually want to use them. Walker discussed several examples of technically impressive systems that failed precisely because they neglected this distinction. Some provided too much information. Others demanded excessive attention. Many ignored the broader contexts within which people operate. A system may be capable of delivering enormous amounts of information, though that does not necessarily mean people want to receive it.

    Questions of accessibility broadened these concerns further. Much of Walker’s work focuses on enabling participation rather than merely providing access. He described projects supporting education for blind students, making scientific information more accessible, and improving experiences within museums and aquariums. These examples revealed another recurring theme. Accessibility is not simply about removing barriers. It is about ensuring that people can engage meaningfully with experiences, opportunities, and ideas.

    His work within museums and aquariums illustrates this particularly well. Modern cultural institutions often provide physical access while leaving informational and emotional access largely unresolved. A blind visitor may be able to enter an aquarium, though the experience remains fundamentally visual. Standing before an enormous tank filled with whale sharks and rays offers little if the most important aspects of the exhibit remain inaccessible. Walker’s team explored ways of using tracking systems, sonification, narration, and auditory displays to communicate not only what was present but what was happening. The objective was not merely to describe the environment. It was to create opportunities for engagement, curiosity, and wonder.

    Educational projects revealed similar concerns. Throughout the lecture, Walker repeatedly returned to the distinction between access and participation. Providing information is only one part of inclusion. Students also need opportunities to explore, question, discover, and develop understanding independently. Whether working with scientific data, classroom materials, museum exhibits, or public spaces, the challenge remained remarkably consistent. How can information be presented in ways that support meaningful engagement rather than passive reception? Accessibility, in this sense, becomes a question of design quality rather than a specialised feature introduced at the end of a project.

    Underlying many of these projects is the field of sonification, the practice of representing information through sound. Walker described sonification as both a design challenge and a research problem. Any attempt to translate data into sound requires decisions about mapping, scaling, timing, context, and interpretation. Should temperature be represented through pitch, loudness, or tempo? How should complex information be organised so that listeners can understand it? These questions have no universal answers. Effective solutions depend upon understanding both the data and the people expected to interpret it.

    One reason sonification remains challenging is that many listeners have relatively little experience interpreting information through sound. Graphs, charts, and maps are familiar cultural forms. Auditory representations are far less common. Designers therefore need to balance learnability with expressiveness. A system may communicate information accurately while remaining difficult to interpret. Conversely, a system may sound appealing while conveying very little. Walker’s research repeatedly demonstrated that effective sonification emerges through iterative testing with users rather than through theoretical assumptions alone.

    Such challenges reveal why Walker remains sceptical of simplistic approaches to auditory design. Throughout the lecture, he criticised the tendency to reduce audio interfaces to collections of arbitrary beeps and alerts. Sound possesses enormous communicative potential, though realising that potential requires careful thought. Designers must consider attention, context, usability, aesthetics, cultural expectations, and human behaviour. A sound that performs well in a laboratory may fail completely in everyday life. A technically accurate representation may prove ineffective if users cannot interpret it.

    The phrase “beeps and bops” became a useful shorthand for this problem. Many technologies employ sound only at the most superficial level, relying upon alerts, warnings, and notifications while overlooking the richer possibilities of auditory interaction. Walker’s work points towards a broader conception of sound, one capable of supporting navigation, exploration, learning, communication, and discovery. The challenge is not simply adding sound to technology. It is designing meaningful auditory experiences.

    Towards the end of the discussion, Walker reflected on what he described as a “failure of imagination” in technology design. Sometimes designers struggle to imagine how people actually live with technologies. At other times, users struggle to imagine possibilities that do not yet exist. Successful innovation requires navigating both challenges simultaneously. Revolutionary technologies rarely emerge through user requests alone. Yet genuinely useful technologies also cannot emerge through engineering in isolation. Design becomes a process of bridging these perspectives.

    Looking back across the lecture, what emerges most clearly is not a story about auditory interfaces but a broader philosophy of design. Sound happens to be the medium through which Professor Walker explores these questions, though the underlying principles extend much further. Navigation systems, auditory menus, museum exhibits, educational technologies, sonification projects, and accessibility tools all reveal the same challenge. Technologies succeed not when they demonstrate technical sophistication but when they become meaningful parts of human activity.

    Perhaps this is why Walker repeatedly resisted framing accessibility as a specialised concern. The challenges faced by blind users, firefighters, drivers, students, museum visitors, and countless others often reveal broader truths about human interaction with technology. Designing for specific needs frequently produces insights that benefit everyone. When designers stop asking what a system can do and start asking what people need, entirely new possibilities begin to emerge.

    Throughout the lecture, examples ranging from spatial navigation to aquarium exhibits pointed towards the same conclusion. Successful technologies rarely begin with devices, software, algorithms, or interfaces. They begin with people. Understanding how people listen, learn, move, explore, communicate, and make decisions provides the foundation upon which everything else is built.

    For Professor Bruce Walker, the future of auditory interfaces does not lie in adding more sounds to the world. It lies in understanding how sound can help people navigate, learn, communicate, discover, and participate more fully in the experiences around them. The technology matters. The research matters. The engineering matters. Yet each ultimately serves a more fundamental question, one that quietly shaped the entire lecture from beginning to end: who are we designing for?

  • How Do We Know What Sounds Good? Dr Geoff Martin on Loudspeaker Design and Human Hearing

    Geoff Martin

    What does a good loudspeaker actually do?

    At first glance, the answer seems obvious. A loudspeaker should reproduce sound accurately. It should introduce as little distortion as possible, deliver a flat frequency response, and remain faithful to the original recording. These ideas are deeply embedded within audio culture. Specifications are compared, measurements are analysed, and products are often judged according to how closely they approach technical ideals. Yet Dr Geoff Martin’s guest lecture at Edinburgh Napier University suggested that the question is considerably more complicated than it first appears. Dr Martin, Principal Tonmeister at Bang & Olufsen, spends much of his professional life developing loudspeakers and television audio systems. Throughout the lecture he discussed cabinet volumes, amplifier power, driver behaviour, diffraction, directivity, prototype development, and measurement techniques. Beneath these technical details, however, lay a much broader question. If loudspeakers are ultimately designed for listeners, then how should engineers balance what can be measured against what people actually hear?

    That question has shaped Dr Martin’s career from the beginning. Before joining Bang & Olufsen, his doctoral work explored what he described as a phenomenological model for acoustic simulation. Rather than attempting to recreate every physical characteristic of a real concert hall, the objective was to create something listeners would perceive as convincing. A simulation could differ from reality in measurable ways while still producing an experience that sounded authentic. This distinction between physical accuracy and perceptual accuracy quietly reappeared throughout the lecture, surfacing in discussions of room acoustics, loudspeaker behaviour, directivity, and listening tests. Although the presentation focused on loudspeaker development, the deeper theme concerned a problem that extends across audio engineering as a whole. Sound is a physical phenomenon that can be measured with extraordinary precision. Listening is a human experience that cannot be reduced quite so easily.

    Much of the lecture examined how a loudspeaker is actually developed. Popular discussions of audio technology often imply that engineers begin with a clear target before gradually refining a design until it reaches perfection. Dr Martin described something rather different. Loudspeaker development begins not with solutions but with constraints. How much will the product cost? How large can it be? How loudly should it play? How low should it reproduce bass frequencies? How much internal volume is available? How much amplifier power can be accommodated? Such questions emerge long before the final product exists. Acoustic engineers, industrial designers, product managers, manufacturers, and marketers all contribute to the process. Every decision influences every other decision. A larger cabinet may improve low-frequency performance while creating industrial design challenges. A smaller enclosure may look elegant while limiting acoustic capability. Additional amplifier power may improve output levels while increasing cost and heat. Loudspeaker design therefore becomes a process of balancing competing priorities rather than pursuing a single ideal.

    For this reason, development proceeds through a series of prototypes. Early versions frequently employ off-the-shelf drivers mounted within simple enclosures that approximate the intended cabinet volume. At this stage, nobody is trying to create the finished product. Engineers are asking questions. Does the concept possess sufficient acoustic potential to justify further development? Is the enclosure volume realistic? Can the desired frequency range be achieved? Dr Martin compared this process to testing an engine outside a vehicle. Nobody is concerned with comfort, aesthetics, or handling characteristics. The objective is to establish whether enough performance exists to make further investment worthwhile. As development continues, the questions become increasingly specific. Drivers are modified. Internal structures change. Cabinet geometry evolves. Diffraction effects emerge. Resonances are identified and controlled. Measurements reveal new problems while prototypes reveal new possibilities. Progress rarely follows a straight line. Instead, the process resembles a conversation between engineering decisions and acoustic consequences, with each iteration producing a slightly deeper understanding of the system being developed.

    What makes this process particularly interesting is that measurements alone never provide all the answers. Loudspeaker development relies heavily upon objective data. Engineers measure frequency response, distortion, directivity, impedance, output capability, and countless other parameters. Without such measurements, development would quickly descend into guesswork. Yet Dr Martin repeatedly returned to a simple observation that changes how these measurements should be interpreted. Real listeners do not experience loudspeakers in anechoic chambers. They experience them in rooms.

    That observation may sound almost trivial, though its implications are profound. When a listener sits in a living room, only part of what reaches the ears comes directly from the loudspeaker. Sound also reflects from walls, ceilings, floors, windows, furniture, and countless other surfaces. Every room participates in the listening experience. A loudspeaker therefore does not simply radiate sound forwards towards a listener. It radiates sound into an environment. Once those reflections begin interacting with direct sound, the listening experience becomes considerably more complicated than a single frequency response measurement might suggest.

    This is why Dr Martin devoted considerable attention to directivity. Many audio discussions focus almost exclusively on what happens directly in front of a loudspeaker. Place a microphone on axis, measure the response, and examine the resulting graph. Such measurements remain important, though they tell only part of the story. Engineers also need to understand how sound is distributed throughout space. How much energy radiates to the sides? How much travels upwards and downwards? How does this behaviour change with frequency? To answer these questions, loudspeakers are measured repeatedly while being rotated through hundreds of positions, producing detailed maps of acoustic radiation. The resulting data reveals how a loudspeaker interacts not only with listeners but also with rooms.

    This shift in perspective transforms the problem entirely. Two loudspeakers may produce remarkably similar measurements directly in front of the listener while sounding quite different in real environments. The reason often lies in what happens away from the central listening position. A loudspeaker that distributes energy broadly throughout a room creates a different pattern of reflections from one that concentrates energy more narrowly. Those reflections influence spaciousness, localisation, tonal balance, and listener perception. Suddenly, the loudspeaker is no longer just a source of sound. It becomes part of a larger acoustic system that includes the room itself.

    At this point the lecture moved beyond engineering and into psychoacoustics. Dr Martin argued that directivity influences more than tonal characteristics. It also shapes how listeners perceive space. Human beings routinely use reflections to estimate the distance of sound sources. Outdoors, where reflections are relatively limited, sounds often appear perceptually closer than equivalent sounds heard indoors. Rooms provide information about scale, distance, and location through the reflections they generate. Loudspeakers participate in these same perceptual processes. A design that radiates energy widely into a room can produce a different impression of distance from one that concentrates energy more narrowly, even when other measurements remain similar.

    One particularly memorable example involved speech reproduction. Under certain circumstances, different frequency components within a voice can appear to occupy slightly different perceptual distances. The recording itself remains unchanged. The effect emerges from the loudspeaker’s changing directivity across the frequency spectrum. Some elements of the voice radiate broadly while others become increasingly directional. Listeners may not consciously identify the source of the discrepancy, though they often perceive something unusual. Once noticed, the effect can become difficult to ignore. Examples such as these reveal why loudspeaker design cannot be reduced to frequency response curves alone. Human hearing does not experience isolated measurements. It experiences integrated perceptual events in which distance, localisation, spaciousness, timbre, and context continuously interact.

    Seen in this light, many of the lecture’s apparently technical discussions acquire a different significance. Cabinet diffraction is not merely a measurement problem. Driver placement is not simply a mechanical decision. Directivity is not just another engineering specification. Each ultimately influences how listeners interpret acoustic information. A loudspeaker cannot be understood solely by examining what happens directly in front of it. It must also be understood in terms of how it interacts with a room and how listeners interpret the resulting acoustic information. Directivity, reflections, diffraction, frequency response, and cabinet design are not independent concerns. They are different parts of the same perceptual problem.

    This helps explain why loudspeaker development remains such an iterative process. Engineers measure, build, listen, modify, and measure again. Each prototype reveals something about the relationship between the physical behaviour of the loudspeaker and the way that behaviour is ultimately perceived. Better measurements improve understanding, though they do not eliminate the need for listening. Listening remains the reason the measurements exist in the first place.

    Looking back across the lecture, what emerges most clearly is not a story about loudspeakers but a story about the limits of measurement. Measurements remain indispensable. Without them modern loudspeaker design would be impossible. Yet measurements alone cannot answer the question that matters most. They can describe what a loudspeaker does. They cannot completely describe what it is like to hear it.

    That gap between measurement and perception is where much of loudspeaker design actually happens.

  • Designing Fear: Matt Yocum on Horror, Tension, and the Psychology of Sound

    Matt Yocum

    What is the fastest way to make a horror film stop being scary?

    Matt Yocum’s answer was immediate: mute it.

    At first, the response feels almost too simple. Horror cinema is often discussed in terms of monsters, visual effects, darkness, violence, or shock. Yet remove the soundtrack and something fundamental changes. The creature remains on screen. The corridor remains dark. The threat still exists. What disappears is much of the tension. Anticipation begins to weaken. The feeling that something terrible might be about to happen gradually fades away. For Yocum, whose career has included sound design work across film and television, this observation reveals something important about the role of sound in horror. Sound design is not simply about creating interesting sounds. It is about shaping emotion. Throughout his guest lecture at Edinburgh Napier University, whether discussing creature design, immersive audio, audience psychology, or jump scares, a remarkably consistent idea emerged. Horror is not primarily about making audiences hear frightening things. It is about making them feel uncertain about what might happen next.

    That distinction helps explain why some of the most effective moments in horror involve remarkably little happening at all. A character walks slowly down a hallway. A door stands slightly ajar. An empty room appears entirely ordinary. Nothing overtly threatening is visible, yet audiences become increasingly uncomfortable. According to Yocum, much of horror operates through tension and release. Viewers are encouraged to anticipate an event before that event actually arrives, and sound plays a central role in constructing that anticipation. Environmental detail begins to disappear. The soundtrack becomes quieter. Attention narrows. Audiences recognise the pattern immediately. Years of watching horror films have taught them that something is coming. A character approaches a door, the atmosphere tightens, and the audience braces itself for the inevitable scare. The door opens and nothing is there. Relief briefly returns, only for the real scare to arrive moments later when attention has already begun to relax. Horror repeatedly exploits this relationship between expectation and uncertainty. Audiences respond not only to what they hear, but also to what they believe they are about to hear.

    Silence therefore occupies a surprisingly important position within horror sound design. Although the genre is often associated with loud impacts and sudden shocks, Yocum argued that removing sound can be just as effective as adding it. As environmental information falls away, attention becomes focused on the sounds that remain. Breathing becomes more noticeable. Footsteps acquire greater significance. The creak of a floorboard suddenly feels loaded with meaning. None of these sounds are inherently frightening. Their significance emerges through context. A footstep heard in a crowded shopping centre communicates something very different from a footstep heard in an empty house late at night. Horror succeeds by manipulating those relationships, encouraging audiences to reinterpret ordinary sounds as signs of vulnerability, danger, or uncertainty. Rather than overwhelming viewers with information, effective sound design often achieves more through careful restraint. The audience begins searching for clues, assigning importance to small details, and constructing explanations from incomplete information. In many respects, horror is less concerned with frightening sounds than with the psychology of listening itself.

    Questions of interpretation also emerged throughout Yocum’s discussion of creature design. Audiences often imagine creature sound as a process of inventing something entirely new, though the reality is frequently more complicated. Effective creature design begins not with software, plug-ins, or signal processing, but with observation. How large is the creature? How does it move? Does it walk, crawl, slither, or fly? Does it possess lungs? How much does it weigh? What sort of anatomy produces its sounds? Such questions help ground fictional beings within believable worlds. Sound gives visual effects a sense of physical presence. A creature that appears enormous on screen can feel surprisingly weightless without appropriate sonic support. Movement, impacts, breathing, and vocalisation all contribute to the illusion that something genuinely occupies space. The task is not simply to create an unusual sound. It is to persuade audiences that a fictional entity belongs within the world they are experiencing.

    One of the most memorable moments in the lecture emerged when a student described creating a creature vocalisation from the sound of a restaurant toilet flush. Rather than dismissing the idea, Yocum praised the approach. Organic source material, he argued, often provides richer creative possibilities than excessive processing. A toilet flush already contains qualities that resemble breathing, resonance, and vocalisation. More importantly, it originates in the physical world. Throughout the lecture, Yocum repeatedly returned to the value of starting with interesting source material rather than attempting to manufacture complexity through endless layers of effects. This preference led naturally into a broader discussion about creative confidence. Early in his career, he admitted that he often attempted to solve design problems through increasingly complex layering and processing. Over time, he recognised a common trap. Designers frequently add more and more material when they become uncertain about their choices. One piece of advice from veteran sound designer Erik Aadahl remained particularly influential: the less confident you are, the more likely you are to throw the kitchen sink at a design. The observation is humorous, though it points towards a deeper truth about creative practice. Effective sound design is rarely an exercise in accumulation. It is an exercise in decision-making. Success depends less upon how many sounds can be added and more upon understanding which sounds genuinely belong.

    A story later in the lecture illustrated this principle perfectly. Working on a film involving a supernatural creature, Yocum spent weeks developing vocalisations based upon detailed descriptions provided by the filmmakers. Numerous versions were presented. None satisfied the directors. More versions followed. Still nothing. Eventually, after countless iterations and experiments, the sound that made it into the final film turned out to be a heavily processed recording of his French bulldog. The story generated laughter, though it also revealed something important about professional practice. Sound design is rarely a straightforward process of technical problem-solving. It often depends upon experimentation, intuition, collaboration, and a willingness to recognise successful ideas when they emerge from unexpected places. Behind the technology, the software, and the increasingly sophisticated production tools lies a creative discipline that remains deeply dependent upon listening, judgement, and imagination.

    Questions of attention remained central throughout the lecture, particularly when Yocum turned towards immersive audio formats such as Dolby Atmos. Discussions of Atmos often focus upon technology. Additional speakers create opportunities for sounds to move around an audience, above them, and through three-dimensional space. Yet one of the more interesting aspects of Yocum’s discussion was the extent to which he resisted treating the technology itself as the primary attraction. Additional channels do not automatically create better storytelling. A sound placed behind the audience is not effective simply because it appears behind them. It becomes effective when its position contributes to the emotional experience of the scene. This principle feels especially relevant to horror. Audiences are often more frightened by sounds they cannot see than by threats directly in front of them. A creak somewhere behind a listener immediately encourages questions. What caused it? How far away is it? Is it moving closer? A sound overhead may suggest a presence occupying unseen space. Rain surrounding a house can make isolation feel more tangible. In each case, the sound itself matters less than the uncertainty it creates. Atmos therefore becomes a storytelling tool rather than a technological showcase. The objective is not to demonstrate that sounds can move around a room. The objective is to shape how audiences imagine the world beyond the frame.

    Many of Yocum’s examples returned to this relationship between hearing and imagination. Horror repeatedly exploits the simple observation that listeners can hear far more than they can see. Sound extends perception beyond the limits of the image. A camera may reveal only a small portion of a location, though audio can suggest activity elsewhere. Something may be moving in another room. A distant voice may imply an unseen presence. A sound above a ceiling can transform an ordinary environment into a potentially threatening one. Once audiences begin constructing explanations for sounds that lack visible sources, imagination becomes an active participant in the storytelling process. Classic horror cinema frequently depends upon this principle. Yocum pointed to Alien as a particularly influential example. Although the creature has become one of the most recognisable monsters in film history, much of its effectiveness emerges from how rarely audiences see it clearly. Sound plays a crucial role in sustaining that uncertainty. The audience hears evidence of the creature’s presence long before receiving a complete visual understanding of what it is. Strange noises, movement within confined spaces, and subtle indications of activity allow imagination to fill gaps that images deliberately leave unresolved. The result is often more effective than direct revelation. Once a threat becomes fully visible, it also becomes more understandable. Horror frequently derives its strength from resisting that certainty.

    A similar logic appeared in Yocum’s discussion of possessed objects and haunted spaces. One example involved whispers gradually drawing a child towards a crack in a wall. Physically, very little is happening. The wall remains a wall. The room remains a room. Yet sound transforms the situation. The whispers encourage audiences to assign significance to something that would otherwise appear entirely ordinary. An inanimate object begins to feel charged with possibility. Attention becomes focused upon a location that images alone could never make equally compelling. Sound therefore contributes not only to atmosphere but also to narrative meaning. It guides audiences towards particular interpretations of what they are seeing.

    What emerged repeatedly throughout these examples was the importance of expectation. Horror does not simply frighten audiences through sudden surprises. It first teaches them how to anticipate those surprises. Once viewers recognise familiar patterns, filmmakers can begin manipulating them. Yocum highlighted Barbarian as a particularly interesting contemporary example. The film repeatedly establishes situations that appear to be moving towards conventional horror outcomes before abruptly changing direction. Audiences believe they understand what will happen next. The film then exploits that confidence. Sound design plays a central role in this process. Expectations must first be established before they can be disrupted. A soundtrack may encourage viewers to anticipate danger in one place while the real threat emerges somewhere else entirely.

    Taken together, these examples reveal a consistent philosophy running throughout Yocum’s lecture. Sound design is not simply concerned with what audiences hear. It is concerned with where they direct their attention, what they expect to happen next, and how they interpret incomplete information. Atmos, creature design, silence, environmental detail, and possessed objects may appear to involve very different techniques, though they frequently pursue the same objective. They encourage audiences to imagine worlds extending beyond what is immediately visible. Horror thrives within that gap between perception and certainty. The less certain audiences become about what lies beyond the frame, the more actively they participate in constructing the experience themselves.

    Looking back across the lecture, what emerges most clearly is a conception of sound design that extends far beyond the creation of individual sounds. Discussions of horror often focus upon monsters, jump scares, disturbing imagery, or technical effects, yet Yocum repeatedly returned to something more fundamental. Sound design is ultimately concerned with emotion. Every creative decision, from the selection of source material to the placement of a sound within an immersive environment, contributes to how audiences experience a story. This perspective helps explain why so many of the lecture’s examples appeared to revolve around expectation rather than spectacle. Silence becomes valuable not simply because it removes sound, but because it changes how listeners interpret what remains. Creature design succeeds not through complexity alone, but through an understanding of physiology, movement, and character. Atmos becomes meaningful when it directs attention towards spaces that audiences cannot see. Even the most effective jump scares depend less upon the scare itself than upon the tension that precedes it. Across each of these examples, sound functions as a way of shaping perception and guiding interpretation.

    Many of the stories shared throughout the lecture pointed towards the same conclusion. A restaurant toilet flush can become the foundation for a creature vocalisation. Weeks of carefully crafted designs may ultimately give way to a recording of a French bulldog. A whisper can transform an ordinary wall into something unsettling. None of these outcomes emerge from technology alone. They emerge from a creative process built upon listening, experimentation, and a willingness to follow ideas wherever they lead. The tools may continue to evolve, though the underlying challenge remains remarkably consistent: understanding how audiences will respond to what they hear. Perhaps this is why horror provides such a revealing lens through which to understand sound design more broadly. The genre exposes processes that are often present in other forms of storytelling but are easier to overlook. Audiences are constantly interpreting sounds, assigning meanings to them, and using them to make sense of the worlds unfolding around them. Horror simply makes those processes more visible. A creak in a floorboard, a distant movement, or a barely audible breath can suddenly become the focus of intense attention. The sounds themselves may be entirely ordinary. What changes is the emotional framework through which they are experienced.

    Returning to Yocum’s opening observation, the fastest way to make a horror film less frightening may indeed be to mute it. Doing so removes far more than sound effects or atmospheric detail. It removes anticipation. It removes uncertainty. It removes many of the subtle cues that encourage audiences to imagine what might happen next. Horror depends upon those moments of expectation, and sound plays a central role in creating them.

    A hallway. A footstep. A whisper from another room. A door slowly opening.

    None of these things are especially frightening on their own.

    Yet in the hands of a skilled sound designer, they can make an entire audience hold its breath.

  • Why Has Pitch Remained So Difficult to Explain? Prof. William Yost on Hearing Science’s Enduring Mystery

    Professor William Yost

    Few aspects of hearing feel more straightforward than pitch. Sounds seem high or low, rising or falling, stable or changing. We recognise familiar voices, detect changes in intonation, distinguish one alarm from another, and effortlessly judge whether one sound is higher than the next. Most of the time, pitch appears so natural that it barely attracts attention. It feels less like an interpretation and more like a property of the world itself. Prof. William Yost’s guest lecture revolved around a deceptively simple question: if pitch feels so obvious, why has it proved so difficult to explain?

    The question has occupied researchers for more than two thousand years. During that time, scientific understanding of hearing has advanced dramatically. Researchers can measure acoustic signals with extraordinary precision, investigate the mechanics of the inner ear in remarkable detail, record neural activity throughout the auditory pathway, and construct increasingly sophisticated computational models of perception. Yet despite all of this progress, pitch remains one of the most debated topics in hearing science. What makes this especially intriguing is that the difficulty does not arise from a shortage of ideas. The history of pitch perception is filled with elegant theories. Again and again, researchers have proposed explanations that appeared capable of accounting for the available evidence. Again and again, new observations have emerged that complicated the picture. The resulting history is not one of scientific failure. It is a story of a percept that repeatedly proves more complicated than researchers initially expect.

    Discussion of pitch often begins with Pythagoras. Observations of vibrating strings suggested that simple mathematical relationships corresponded to differences in perceived pitch, encouraging the belief that pitch might ultimately be explained through measurable physical properties. Centuries later, researchers such as Hermann von Helmholtz developed increasingly sophisticated accounts linking acoustics, physiology, and perception. Progress seemed to move steadily towards a complete explanation. Yet the history presented by Prof. Yost repeatedly demonstrated that confidence in any single account rarely lasted for long. New experiments continued revealing sounds that behaved in unexpected ways, exposing limitations in explanations that had previously appeared convincing.

    Among the most influential examples is the phenomenon now known as the missing fundamental. Listeners can perceive a pitch corresponding to a frequency that is physically absent from the sound itself. Telecommunication systems have long benefited from related principles. Even when low frequencies are poorly transmitted, listeners can often continue perceiving aspects of the missing pitch through the remaining harmonics. At first encounter, the phenomenon sounds almost impossible. How can listeners hear a pitch that is not present within the signal? Its importance extends far beyond its novelty. The missing fundamental revealed that pitch could not be explained simply by identifying which frequencies were physically present. The auditory system appeared capable of generating a stable perceptual experience even when information that seemed essential was absent. A phenomenon that initially appeared to be a curious exception gradually became evidence that researchers might be asking the wrong questions. Observations of this kind repeatedly changed the direction of pitch research. Their significance lay not merely in producing unusual percepts but in exposing hidden assumptions about how hearing operates.

    Researchers naturally searched for the critical variable that would finally explain pitch. Sometimes that variable appeared to be frequency. Sometimes it appeared to be temporal periodicity. Sometimes it appeared to be harmonic structure. Each candidate captured something important about hearing. Each eventually encountered observations that it struggled to explain. Scientific explanations often become more satisfying as they become simpler, and much of the history of pitch research can be understood as a search for a unifying principle capable of accounting for a wide range of perceptual experiences. Every successful theory illuminated part of the phenomenon while leaving other aspects unresolved. Rather than steadily converging towards a single universally accepted explanation, the field gradually accumulated evidence that several different forms of information contribute to what listeners experience as pitch.

    Contemporary hearing science reflects this growing recognition. Spectral information contributes to perception. Temporal patterns contribute as well. Envelope cues can also play a role under certain conditions. Each source of information appears capable of supporting aspects of pitch perception, though each also possesses limitations. The challenge therefore becomes less about identifying a single cue and more about understanding how different forms of information interact to produce a percept that listeners experience as unified and stable. That challenge becomes even greater once the nature of sound itself is considered. Sound unfolds rather than existing all at once. A listener cannot determine the intonation of a spoken sentence from a single instant of sound. The rising contour that transforms a statement into a question only becomes apparent once enough of the signal has unfolded. Similar constraints apply more broadly throughout hearing. A pressure wave travels through the environment, reaches the ear, interacts with the auditory system, becomes encoded into neural activity, and undergoes further processing before contributing to conscious experience. Many of the acoustic cues associated with pitch require information to accumulate before they become meaningful. The auditory system therefore cannot rely upon an instantaneous snapshot of the world. Instead, it must integrate information distributed across time while maintaining perceptual stability.

    Listening never occurs under perfectly controlled conditions. Every listener brings a unique physiology, a unique listening history, and a unique set of experiences to the task of perception. Consider how differently a trained musician, a young child, and an older listener with age-related hearing loss may encounter the same sound. Languages emphasise different pitch patterns. Hearing changes across the lifespan. Exposure to speech and environmental sounds varies considerably. Acoustic environments introduce further variability through reverberation, masking, reflections, distance, and background activity. Signals reaching the ear are therefore rarely identical from one situation to the next. Yet despite this variation, listeners often arrive at strikingly similar perceptual judgements. Understanding how such stability emerges remains part of the broader challenge confronting pitch research.

    Relative pitch offers another perspective on why the problem remains difficult. Most people can readily determine whether one sound is higher or lower than another, recognise familiar patterns across changing circumstances, and detect subtle shifts in vocal expression. A familiar voice remains recognisable whether the speaker is tired, excited, whispering, or shouting. A simple melody can remain recognisable when sung by different people starting on different notes. The acoustic details change, though listeners continue perceiving stable relationships. Absolute pitch, by contrast, appears comparatively uncommon. Hearing therefore seems especially effective at identifying patterns and relationships rather than fixed reference points. Such relational perception proves enormously useful in a world where sounds vary continuously according to source, context, and environment, though it complicates attempts to explain pitch through simple correspondences between physical signals and perceptual experience.

    Contemporary research continues uncovering percepts that challenge established assumptions. Prof. Yost’s discussion of Iterated Ripple Noise provided a particularly striking example. Such stimuli can generate robust pitch percepts despite possessing characteristics that many traditional theories would not predict. Listeners report clear pitches even when the sounds themselves bear little resemblance to the simple tones often associated with textbook demonstrations. Their importance lies in showing that the history of pitch research is not merely a story of earlier misunderstandings corrected by later discoveries. New observations continue emerging. New stimuli continue revealing unexpected aspects of perception. More than two thousand years after researchers first began asking how pitch works, the auditory system still has surprises to offer.

    Scientific uncertainty occupied an unusually prominent place throughout the lecture. Many guest lectures focus on a particular discovery, method, or contribution. Prof. Yost approached the subject differently. Rather than presenting pitch as a problem approaching resolution, he presented it as a continuing scientific conversation extending across centuries. Researchers separated by generations appeared not as competitors replacing one another but as participants in a shared effort to understand a percept that repeatedly exceeds expectations. There was a striking absence of triumphalism in this account. Successive theories were not presented as failures to be discarded, nor as final answers waiting to be celebrated. Instead, they became stages in an ongoing attempt to understand one of the most familiar yet elusive aspects of hearing. New methods produce new insights while simultaneously revealing new complications. Better measurements reduce some uncertainties while exposing others. The enduring value of pitch research therefore lies not only in the answers it has generated but also in the questions it continues to produce.

    Seen from this perspective, pitch becomes something larger than a specialised topic within psychoacoustics. Researchers can measure sounds with extraordinary accuracy. They can investigate increasingly detailed aspects of auditory physiology and neural processing. Connecting those physical processes to lived perceptual experience remains challenging. More than two thousand years of investigation have not diminished the significance of the problem. If anything, they have expanded it. New methods reveal additional layers of hearing, while new explanations illuminate important aspects of auditory processing without resolving every question.

    What emerged most clearly from Prof. Yost’s lecture was that the enduring importance of pitch lies not merely in discovering which theory ultimately proves correct. Its value lies in what the search has revealed about hearing itself. The history of pitch perception is often described as a succession of competing theories, though the lecture presented something richer than that. It revealed generations of researchers grappling with the same fundamental puzzle, each contributing part of a much larger conversation. The closer researchers look at pitch, the less it resembles a single problem waiting to be solved and the more it resembles a window into the sophistication of auditory perception. Few scientific questions have persisted for so long. Fewer still continue generating new experiments, new explanations, and new debates. That persistence suggests that researchers are not simply refining an existing answer. They are continuing to uncover new dimensions of the question itself.

  • Beyond the Frequency Response: Dr Nick Zacharov on Why Sound Quality Refuses to Stay Simple

    Sound quality appears to be something that should be relatively easy to define. Modern audio engineering has become remarkably precise, allowing engineers to measure frequency response, distortion, sound pressure level, impulse response, and countless other properties with extraordinary accuracy. Pages of graphs and measurements can describe how an audio system behaves in minute detail. Looking at these increasingly sophisticated tools, it becomes tempting to assume that the problem has largely been solved. Better systems should produce better measurements, while increasingly detailed measurements should gradually lead towards better listening experiences.

    Yet most people who spend time with sound eventually encounter an uncomfortable contradiction. A new pair of headphones may arrive with impressive specifications and glowing reviews, promising exceptional clarity and technical accuracy. Everything appears correct on paper, yet after listening for a while something feels slightly wrong. Another pair with less impressive measurements somehow sounds more engaging, or perhaps two products that appear remarkably similar perform very differently in practice. Even more confusingly, people listening to exactly the same material can disagree entirely about what they hear. Experiences like these raise an interesting question. If sound can already be measured with extraordinary precision, why do we still need people to listen?

    This question formed the starting point of an online guest lecture delivered by Dr Nick Zacharov, whose work has spent more than three decades exploring sound quality and sensory evaluation across industries including telecommunications, professional audio, and product development. As co-founder of AudioSense Lab, his work focuses on understanding how people experience sound rather than simply measuring the physical properties of signals. Across the lecture, one idea gradually became increasingly clear: sound quality is not hidden solely within the signal itself. It also emerges through the relationship between sound and the people hearing it.

    Part of the challenge begins with assumptions about hearing itself. Measurement systems generally behave in predictable ways. Microphones can be calibrated, repeated measurements can produce highly consistent results, and instruments respond reliably under controlled conditions. Human hearing behaves rather differently. Rather than functioning as a neutral recording device, the auditory system continuously interprets incoming information before we consciously become aware of it.

    Zacharov described hearing as an extraordinarily sophisticated process operating across enormous ranges of frequencies and intensities. Sounds arriving from different directions interact with the shape of the head and ears before even reaching the inner ear, while loudness, timing, and spatial position all influence the information ultimately reaching the brain. Listening therefore involves more than passively receiving information from the outside world. The auditory system actively reconstructs what we hear, continually shaping experience rather than simply recording it. Measuring sound pressure level may therefore be relatively straightforward, though measuring how people actually experience sound quickly becomes much more complicated.

    This issue becomes clearer when considering the language people commonly use to describe audio experiences. Terms such as brightness, warmth, spaciousness, clarity, depth, and fullness often feel straightforward and intuitive, and most listeners immediately recognise what these ideas mean. Yet many of these qualities do not correspond directly to simple physical measurements. Loudness provides a useful example. Loudness is not merely a sound pressure value but a perceptual experience allowing listeners to organise sounds along a continuum extending from quiet to loud. Anyone who has increased the volume of a quiet dialogue scene in a film only to be startled moments later by a sudden explosion or a swelling piece of music has experienced this distinction directly.

    Similar relationships exist for many of the characteristics listeners use when evaluating sound systems. Spaciousness involves more than physical distance between sound sources, warmth cannot simply be reduced to a particular frequency range, and clarity often emerges through interactions between multiple factors rather than a single measurable value. Describing sound therefore becomes surprisingly complicated. People often use similar words while imagining different things. One listener’s idea of warmth may not correspond exactly to another person’s understanding of the same term. Researchers and designers therefore face the challenge of developing shared vocabularies that allow experiences to be discussed more consistently.

    This need for a common language has led researchers towards the development of perceptual descriptors and sensory lexicons. Rather than relying on vague impressions such as “good” or “bad”, listeners are encouraged to think in terms of more specific qualities that can be identified repeatedly. The aim is not simply to produce more words for describing sound. Instead, the goal is to create reliable ways of connecting subjective experiences with measurable characteristics. The question therefore shifts again. Rather than asking whether sound itself can be measured, attention moves towards understanding whether measurements adequately describe the experiences listeners actually care about.

    One of the most interesting ideas discussed during the lecture emerged through a distinction between preference and perception. Initially these concepts seem almost interchangeable. If somebody prefers one sound over another, it appears reasonable to assume that the answer provides everything necessary. Preference feels direct and uncomplicated. Yet preference quickly becomes more unstable than it initially appears. People notice different details, bring different expectations into listening environments, and respond differently depending on context. Prior experiences shape listening behaviour, while cultural backgrounds and individual habits influence interpretation. Preferences can also change over time, meaning two listeners hearing exactly the same material can arrive at entirely different conclusions.

    To explain this distinction, Zacharov introduced an example involving cheese. Imagine placing several cheeses in front of a group of people and simply asking which one they prefer. Most people would answer almost immediately. The process feels natural and instinctive. Yet the situation changes once different questions begin appearing. Which cheese feels creamier? Which one seems more acidic? Which has a stronger texture? Attention gradually moves away from simple preference and towards analysis. People begin thinking differently about the experience itself.

    Listening behaves in much the same way. Zacharov noted that if people are simply asked what they prefer, they often respond immediately and instinctively. Once listeners are instead asked to evaluate characteristics such as distortion, bass, or other specific attributes, something changes in the listening process itself.

    “If I ask people what they prefer, they will instantly tell you. If I ask them to evaluate distortion and bass and all of these different characteristics, they start thinking consciously about things.”

    What initially appears to be a relatively small distinction gradually becomes much more interesting. Once people become consciously aware of what they are listening for, their relationship with sound itself begins changing. They are no longer responding naturally in the same way they might during everyday listening. Instead, they begin examining specific characteristics and separating experiences into individual components. Listening effectively becomes analytical rather than instinctive.

    This distinction sits at the centre of sensory evaluation. Rather than asking people simply whether they like something, sensory evaluation attempts to understand how people perceive particular characteristics and why those characteristics influence experience. The goal is not merely to identify winners and losers but to understand the qualities shaping listening itself.

    Zacharov described how this often involves training listeners to recognise and describe perceptual attributes systematically. This process does not necessarily involve teaching people what they should hear. Instead, it focuses on developing consistency. Listeners learn to identify particular forms of distortion, tonal differences, changes in spatial presentation, or other relevant characteristics. Over time, they develop a shared vocabulary allowing listening experiences to be discussed with greater precision.

    Training becomes particularly important since untrained listeners often respond differently from experienced listeners. Someone listening casually may immediately focus on broad impressions such as whether a sound feels enjoyable or unpleasant, while trained listeners may identify subtle changes in bass response, timbral colouration, spatial width, or artefacts introduced by processing systems. Neither response is inherently better than the other, though they provide different forms of information. One reflects instinctive experience while the other provides analytical detail.

    These methods become particularly valuable within product development. Preference testing can identify whether people generally favour one system over another, though such tests often reveal relatively little about why decisions occur. A product may consistently outperform competitors while leaving important questions unanswered. What exactly are listeners responding to? Greater spaciousness? Reduced distortion? Increased clarity? Better balance?

    Sensory evaluation attempts to bridge this gap by identifying the characteristics influencing perception, allowing researchers and designers to understand not simply whether products succeed but why they succeed. These approaches have applications across a wide range of industries. Telecommunications systems aim to optimise speech quality and intelligibility. Headphone manufacturers seek desirable listening experiences across different musical styles. Automotive companies increasingly design not only engines and interiors but also the sonic experience of travelling within vehicles. Consumer technologies ranging from smart speakers to voice assistants similarly depend on understanding how people perceive sound rather than simply reproducing signals accurately.

    Towards the end of the lecture, another issue gradually emerged concerning the relationship between controlled testing environments and everyday listening experiences. Listening tests often take place under carefully designed conditions intended to isolate variables and remove distractions. Such environments are extremely useful for identifying subtle differences and maintaining consistency, yet real listening situations rarely behave in the same way.

    People do not spend their lives sitting silently in isolated rooms rapidly switching between competing systems. Sound exists alongside movement, conversations, expectations, distractions, and activities unfolding simultaneously. Headphones are used on trains and buses, music accompanies exercise and travel, and films are experienced within social environments rather than laboratories. A technically ideal system under laboratory conditions may therefore not necessarily produce the same experience within everyday contexts.

    This raises questions surrounding ecological validity, a concept concerned with how closely experimental conditions resemble real-world experiences. Zacharov reflected on this as an increasingly important direction for future work, suggesting that listening research has gradually begun moving towards broader and more realistic forms of evaluation.

    “I think there is a trend in going more holistic nowadays and going more ecological.”

    Running throughout the lecture was a wider point. Sound quality is not simply a technical problem waiting to be solved through increasingly detailed measurements. Measurements remain essential and enormously valuable, though they only describe part of the listening experience. Signals, technologies, environments, expectations, and listeners continuously interact with one another. Understanding sound therefore may involve more than measuring systems accurately. It may also require understanding the people hearing them.

  • Listening Between Worlds: Dr Ximena Alarcón on Deep Listening and Sonic Migrations

    Dr Ximena Alarcón

    Migration is often described through borders, journeys, and distances travelled. People leave cities, cross countries, settle elsewhere, and gradually build new lives. Less often do we ask what migration sounds like. Yet movement between places changes more than physical location. Familiar sounds disappear from everyday life while new ones slowly become woven into routine experience. Voices remain in memory long after people and places have gone, and certain sounds can unexpectedly return us somewhere we thought we had left behind.

    During an online guest lecture, Dr Ximena Alarcón explored these less visible experiences through sound, asking whether listening might reveal dimensions of migration that geography alone struggles to capture. Drawing on her own experiences of moving from Colombia to Europe, alongside years of artistic and research practice, she explored how listening can become a way of understanding relationships between people, places, and memory.

    Dr Alarcón is a sound artist, researcher, and Deep Listening practitioner whose work combines collaborative performance, sound art, memory, and digital technologies. Across these projects and reflections, one idea repeatedly surfaced: listening is not simply an act of hearing sounds that already exist around us. It can also become a way of tracing experiences, understanding relationships, and making sense of where we belong.

    Many of these ideas first developed through an apparently ordinary experience. After growing up in Bogotá and later encountering underground transport systems in European cities, Alarcón became increasingly interested in the environments created by these systems. Most people barely notice them. Announcements repeat endlessly, trains arrive and disappear, and routine eventually turns entire spaces into background activity. Daily commuting often becomes something we stop consciously hearing. Yet beneath that familiarity, people continue forming subtle relationships with the spaces around them, carrying emotions, frustrations, routines, and memories through these environments day after day. Alarcón became interested in what kinds of traces these repeated experiences might leave behind.

    This question developed into Sounding Underground, a project exploring underground systems in London, Mexico City, and Paris. Participants recorded journeys, selected sounds they considered meaningful, and reflected on the experiences attached to them. Rather than documenting transport systems themselves, the project explored relationships formed through listening.

    “What memories have people when they listen during routine journeys?”

    Responses revealed something surprising. Participants recognised common rhythms and textures across different cities while also identifying details that felt distinctive to each place. One participant described experiencing the three underground systems as though they formed a single connected network rather than separate environments. Sounds that would usually disappear into the background of everyday life suddenly felt more intimate. Mechanical noises, station announcements, and passing voices acquired emotional significance, becoming linked with memory and familiarity in ways that might otherwise remain unnoticed.

    Questions that initially centred on transport systems gradually grew more personal. Listening repeatedly to memories of movement raised another question that redirected Alarcón’s work entirely: “I would like to listen to my own migration.” Attention moved away from cities themselves and towards the experiences carried through them. The question was no longer simply how environments sound, but how memories, identities, and relationships continue shaping listening long after movement has taken place. This transition led Alarcón towards Deep Listening, a practice developed by Pauline Oliveros that encourages expanded awareness of sound, body, memory, and environment.

    Deep Listening extends beyond identifying sounds within a space. Listening becomes connected with silence, bodily awareness, dreams, movement, and relationships with others. Alarcón described keeping dream diaries as part of this process, recording fragments of dreams before they disappeared into waking life. Listening was no longer directed only towards external environments. It became a way of tracing relationships between memories and experiences that might otherwise pass unnoticed. Migration consequently began to appear as something more complex than movement between locations. Memories from different places continue existing alongside present experiences, while voices from the past remain present within current surroundings. Different versions of ourselves emerge over time rather than simply replacing one another.

    Language became an important part of this exploration. During the lecture, Alarcón reflected on the experience of moving between English and Spanish, describing how speaking different languages can sometimes feel like moving between different versions of oneself.

    “When you speak more than one language, you start to create a different personality when you switch between languages.”

    Many people who speak more than one language immediately recognise this feeling. Words change, though something else changes as well. Rhythm changes, gesture changes, and emotional expression often shifts in subtle ways. Certain ideas suddenly become easier to express while others seem to disappear entirely. Alarcón described this through the idea of the “nomadic voice”, suggesting that migrants often inhabit spaces that are neither entirely one place nor another. Instead, memories, identities, and experiences overlap and remain in motion, creating what she described as in-between spaces.

    Questions about memory and identity eventually expanded beyond individual experience. If listening could reveal something about personal migration, could it also create meaningful connections between people separated by geography? This question shaped projects such as Letters and Bridges and Migratory Dreams, where participants in different countries exchanged letters, shared dreams, recorded sounds, and developed collaborative sonic performances across distance. Unexpectedly, participants often described feeling close to people they had never physically met.

    One of the most memorable moments emerged during Migratory Dreams. Participants in Bogotá perceived London as sonically dense and heavily urban. During performances they instinctively introduced sounds of nature, almost as if attempting to return something they felt migrants living in London had lost. Across continents, participants were not simply exchanging sounds or creating performances. Listening had become a way of caring for distant people through shared experience.

    Although these projects emerged through experiences of migration, the ideas discussed throughout the lecture extend far beyond migration itself. Sound design often focuses on realism, immersion, and technical precision, yet Alarcón’s work suggested broader possibilities. Sound can preserve memory, support identity, and create relationships between people separated by distance.

    Migration, in this sense, may involve more than moving between places. Physical journeys eventually end, yet the quieter journeys shaped by memory, identity, and listening often continue long afterwards. Alarcón’s lecture suggested that people do not simply travel across spaces. They also continue travelling through experiences, relationships, and sounds that remain with them long after they arrive.