Preface

Why Sound Design Is Critical to Successful Products

For something so key to the human experience, we have few words to describe the types of sound available to us. This is why we often see user-centered sound design fall by the wayside, leaving customers with detractive results. This book is designed to bridge gaps in terminology and illuminate aspects of sound and sound design. A well-designed interface using sound can be profoundly effective, conveying nuance as well as emotion and urgency, without adding to the visual clutter that characterizes modern technology. We have many benchmarks and concepts for visual design. It is important for us to have frameworks and terminology for sound design as well. With better guidelines, technology can be more calming and human-centered.

Why Does Sound Matter?

Sound is emotional: Because hearing is passive and immediate, it is capable of producing an emotional response irrespective of the intention of the human experiencing it. Music and voice can affect our emotions directly and without interpretation. The sound of light rain falling on a summer day can elicit a sense of calm and ease. Listen to Amália Rodrigues singing “Estranha Forma de Vida” and see if you can resist slipping into melancholy, even if you do not understand the words.
Sound is informative: Many of our responses to sound are hardwired by our physiology. These innate responses range from momentary distraction to delight to a fight-or-flight response.
Sound is a powerful brand differentiator: Well implemented, sound allows a product to stand out; poorly implemented, it detracts. Just as with a visual user interface, sound should cultivate a consistent impression across products and platforms. Auditory cues can be subtle, leaving us without a distinct impression of any one sound, but when they complement the other aspects of design, they can leave us with a deep sense of satisfaction and cohesion. This can produce a successful brand identity.
Sound can ease cognitive burdens: We build more and more products every year, and our environments are more the result of human than natural processes. Our attention is already overloaded, and rather than taking some of the cognitive load off our beleaguered brains, undesigned sounds often add to the burden. Digital recording and playback marks an advancement over analog instruments in that it lets us produce and share music even more easily. But this ease of access comes with drawbacks, such as the loss of communal listening and the loss of sound quality due to compression. Today it is rare to hear full, natural music as we might in a chamber music hall. Instead, we most often hear music that is processed so it can be listenable at low bit rates, making it relatively easy to stream, but diminished in terms of quality. This places a hidden cognitive burden on our brains, which must work to fill minuscule gaps in the music left by the compression process. This is the pragmatic argument for improving our sound design capabilities. With better sound and less compressed audio, we can create more productivity with less effort.
Sound impacts productivity: We have evolved to expect a certain level of background noise, and a certain level of variability: nature is rarely silent, but it is also rarely loud, and loud noises in nature often indicate danger. Because of this, sound can impact our behavior and productivity in a dramatic way. It is difficult to focus on a task when part of your brain is sensing danger, but it is also easy to dismiss these effects when no actual danger is present. For these reasons, sound has an extraordinary ability to influence our experience of tasks, promoting or sapping concentration, creativity, and resolve.

This book is written to be useful to anyone who wants to design or improve on the auditory experience of a new or existing product. It is for anyone who needs to determine when, where, or how sounds are used. From executives to product managers, designers, and developers, and from entrepreneurs to integrated device manufacturers, this book is intended to be the introduction to sound design that non–sound engineers can put to use. We hope it will lead to a better sonic experience for all of us.

The Subjective Nature of Sound

The first step to designing sound is to have a solid understanding of how sound works. We can draw on this knowledge to use sound in products, experiences, and environments (adding, changing, or removing it) in a way that is better for everyone.

Many references speak mainly about the physical phenomena of sound, while we are almost certainly thinking of sound in subjective terms—how we perceive it. When a reference switches back and forth between objective, physical concepts (like sound pressure level, wavelengths, and frequency) and subjective, perceptual ideas (like loudness and pitch) without indicating that it is doing so, the entire subject becomes muddled. In this book, we try to explicitly call out the objective and the subjective aspects of sound.

Audio engineering is complex and challenging because it must work with the distortions introduced by our unique auditory faculties. Some of the frustration between sound engineers and their clients may stem from the fact that these complexities are not commonly understood outside of the field. References often discuss sound as if it were as simple as compressions of air with different strengths and different frequencies, but when it comes to how we hear sound, this is simply not the case.

Our hearing treats the physical phenomena of sound as though interpreted through a funhouse mirror. Sounds of the same physical energy (sound pressure waves, measured in decibels) are heard as differing in loudness depending on their frequency. The same frequency is perceived as a different pitch depending on how loud it is. Sounds that are short enough don’t sound like tones at all, but instead sound like a “click.” All of this becomes confusing when we are trying to talk about sound.

Learning How to Listen

Anyone who makes decisions about how something sounds should be equipped with good listening skills. How else will they be able to put themselves in the shoes of their customers? Listening is a skill that needs to be learned. It takes time and conscious effort. Practice listening to your environment. Understanding music can certainly help you design better, but it is important to pay attention to sounds in your environment.

Recording sound will allow you to gather a more sophisticated palette to work with. Record the little things in life: the sound of footsteps in a hallway with carpet and without, what voices sound like in a restaurant with a lot of reverb, or the sounds that children make versus adults. Record lawn mowers, engines, and dogs; boats and cars and weather. See what it sounds like when you record a car from behind a concrete wall versus right next to it. See how machines sound different from different angles, and whether you are closer to the source or farther away from it.

You can use a digital recorder (Figure P-1) or record on a phone with an app, using .wav or .aiff format. This is important because, unlike .mp 3 files, which compress the audio, .wav and .aiff files are larger, are higher resolution, and can give you a much better understanding of sound during recording and a visual display of the sound waves. Some mobile apps, like Twisted Wave Recorder, allow for recording and playback. Record at a high resolution of 44.1 KHz. Download free software like Audacity or WavePad. Then play with recording!

Remember that, while hearing is passive, listening is an active experience. Being able to listen and not just hear is one of the skills that distinguish a truly effective designer.

Figure P-1. A Zoom brand digital recorder (image courtesy Aaron Day)

Sound should work with us, not against us. The best technologies get out of our way and let us live our lives. As the world gets noisier, a greater understanding of how sound affects us is more and more important. When we design sound instead of just including it in our projects, we’re improving the auditory experience for all who come into contact with our work. Hopefully this book will teach you how to understand, work with, and improve the auditory experience and how crucial it can be for products in everyday life. If you’d like to learn more, visit designingwithsound.com, Amber Case’s site at caseorganic.com and calmtech.com, and Aaron Day’s site at aaron-day.com. Be curious. Be patient. Be brave. Listen.

Let’s begin!

How This Book Is Organized

Part 1: Principles and Patterns of Sound Design

Chapter 1, Opportunities in Sound Design: This chapter covers past, present, and upcoming advances in sound design—including leveraging sound’s effect on our sense of taste and using sound to provide wireless power—and discusses other overlooked areas of how sound can enhance our relationship with the world.
Chapter 2, Subtractive Sound Design for Products: This chapter covers techniques and principles of designing quieter products, starting with innovations pioneered by the automotive industry. Topics span from creating a good fit between components, minimizing unoccupied space, and adding sound-absorbing materials to adding containers and Helmholtz cavities to dampen sounds. The chapter finishes with a discussion of how vibration and turbulence can add unwanted sound to products, and how to design products in a way that reduces these sources of noise.
Chapter 3, Adding Sound to Interactions: A good sound designer knows when to add and when to take away. This chapter covers a set of guidelines for adding sounds to interactions, which can be done with the aim of improving the user experience, augmenting displays, or enhancing environments.
Chapter 4, Removing Sound from Interactions: This chapter covers a set of guidelines for removing sounds from interactions. At times, reducing sound in the interaction is the best way to improve the user experience of a product. This approach can often save costs by reducing development time for new sounds. Knowing when to take away can be an extremely effective skill.
Chapter 5, Sound and Brand: This chapter provides some guidelines for creating and working with sound and brand for both physical and digital products. Anything that produces sound is an extension of a brand, including keystroke sounds, the acoustics of tapping on a device, and what it sounds like to drop, unwrap, or use a device.
Chapter 6, Designing Voice Interfaces: This chapter covers how to design a voice persona and other considerations for the voice in voice interfaces.

Part 2: The Sound Design Process

Chapter 7, Interviewing: This chapter covers how best to interview stakeholders, engineers, and anyone else involved in the development process.
Chapter 8, Design: This chapter provides an overview of how to create a deliverable table and design document. The audit process helps you discover limits, landscape, and opportunities for design. You’ll learn how to specify your design, and get buy-in on deliverables.
Chapter 9, Prototyping: It is often faster and less expensive to test sounds before they are put into the final product. This chapter provides an overview of some helpful prototyping methods, such as interactive palettes, video with sound overlays, video with paper prototypes, animation, and real-world prototypes.
Chapter 10, Hardware Testing: Once a prototype is made, it should be tested. Testing helps evaluate not just the performance, but the character of the audio hardware as well. This chapter covers how to test target hardware, what issues you might encounter and how to solve them, as well as final tuning and synchronization.
Chapter 11, User Testing: This chapter covers methods that can help inform, change, and validate design ideas, as well as research, preproduct testing, prototype testing, in-person and contextual. User testing in context is crucial for the success of sound design projects.

Vocabulary

We have found that a basic overview of the definitions of terms is one of the fastest ways to make people new to sound more comfortable discussing the topic. Consider this a brief sampling of different topics in sound. We have intentionally de-alphabetized the glossary terms in order to make them more accessible and enjoyable to read. We hope the reader will get far more use out of the book because they have these definitions in mind and can refer back to them if needed. The definitions are excerpted from J. Gordon Holt’s Audio Glossary (Audio Amateur Press), with permission.

Qualities of Sound

qualifier: An adjective which the listener attaches to an observed sonic imperfection (such as “peaky” or “muddy”) in order to convey a sense of its magnitude. “Subtle” and “conspicuous” are qualifying adjectives. See “audibility.”
sheen: A rich-sounding overlay of velvety-smooth airiness or guttiness. A quality of outstanding high-frequency smoothness and ease.
rosinous (or resinous): Describes the “zizzy” quality of bowed strings, particularly of cellos or violas.
gutty: Rosinous.
bloom: A quality of expansive richness and warmth, like the live body sound of a cello.
presence: A quality of realism and aliveness.
body: A quality of roundness and robustness in reproduced sound. “Gutsiness.”
gutsy: Ballsy.
cool: Moderately deficient in body and warmth, due to progressive attenuation of frequencies below about 150Hz.
cold: The same as “cool,” only more so. Having somewhat excessive upper-range output and weak lower-range output.
thin: Very deficient in bass. The result of severe attenuation of the range below 500 Hz.
sparse: Less cold than “pinched” but more than “thin.”
thick: Describes sodden or heavy bass.
turgid: Thick.
clean: Free from audible distortion.
body sound: Of a musical instrument: the characteristic sound of the material of which the instrument is made, due to resonances of that material. The wooden quality of a viola, the “signature” by which a brass flute is distinguishable from a wooden or platinum one.
euphonic: Pleasing to the ear. In audio, “euphonic” has a connotation of exaggerated richness rather than literal accuracy.
dissonant: Unpleasant to the ear; ugly-sounding. Dissonance is an imperfection only when the music is not supposed to sound dissonant. Compare “consonant.”
consonant: Agreeable to the ear; pleasant-sounding. Compare “dissonant.”
smooth: Sound reproduction having no irritating qualities; free from high-frequency peaks, easy and relaxing to listen to. Effortless. Not necessarily a positive system attribute if accompanied by a slow, uninvolving character.
tipped-up: Having a rising high-frequency response.
toppy, toppish: Tipped-up. Slightly “tizzy” or “zippy.”
zippy: A slight top-octave emphasis. See “toppy, toppish.”
hot: Very tipped-up high frequencies.
golden: A euphonic coloration characterized by roundness, richness, sweetness, and liquidity.
haze, haziness: A moderate smearing of detail and focus. The audible equivalent of viewing something through a gauzy veil or a dirty window.
sweet: Having a smooth, softly delicate high end.
treacly: British for syrupy.
chocolatey: Like “syrupy,” but darker and more full-bodied.
syrupy: Excessively sweet and rich, like maple syrup.
aggressive: Reproduced sound that is excessively forward and bright.
muffled: Very dull-sounding; having no apparent high frequencies at all. The result of high-frequency roll-off above about 2 kHz.
coarse: A large-grained texturing of reproduced sound; very gritty. The continuum of reproduced sound seems to be comprised of large particles. See “texture.”
grunge: Sonic dirt, crud, roughness. Muffled grittiness.
liquid: Textureless sound.
glassy: Very bright.
harsh: Gratingly unpleasant to the ear.
texture, texturing: A perceptible pattern or structure in reproduced sound, even if random in nature. Texturing gives the impression that the energy continuum of the sound is composed of discrete particles, like the grain of a photograph.
rough: A quality of moderate grittiness, often caused by LP mistracking.
gritty: A harsh, coarse-grained texturing of reproduced sound. The continuum of energy seems to be composed of discrete, sharp-edged particles.
grainy: A moderate texturing of reproduced sound. The sonic equivalent of grain in a photograph. Coarser than dry but finer than gritty.
dry: 1) Describing the texture of reproduced sound: very fine-grained, chalky. 2) Describing an acoustical space: deficient in reverberation or having a very short reverberation time. 3) Describing bass quality: lean, overdamped.
spiky: Pertains to a coarse texturing of sound characterized by the presence of many rapidly recurring sharp clicks. Like the sound of tearing cloth, only crisper.
chalky: Describes a texturing of sound that is finer than grainy but coarser than dry. See “texture.”
snap: A quality of sound reproduction giving an impression of great speed and detail.
slam: (British) Impact.
boomy: Characterized by pronounced exaggeration of the midbass and, often, dominance of a narrow range of bass frequencies. See “one-note bass.”
naturalness: Realism.
sodden, soggy: Describes bass that is loose and ill-defined. Woolly.
woolly: Pertains to loose, ill-defined bass.
loose: Pertains to bass which is ill-defined and poorly controlled. Woolly.
lush: Rich-sounding and sumptuous to the point of excess.
open: Exhibiting qualities of delicacy, air, and fine detail. Giving an impression of having no upper-frequency limit.
billowy (also “billowing”): Excessively reverberant.
plummy: (British) Fat, rich, lush-sounding.
airy: Pertaining to treble which sounds light, delicate, open, and seemingly unrestricted in upper extension. A quality of reproducing systems having very smooth and very extended high-frequency response.
dynamic: Giving an impression of wide dynamic range; punchy. This is related to system speed as well as to volume contrast.
congested: Smeared, confused, muddy, and flat. Totally devoid of transparency.
sock: A quality of sound reproduction giving a sensation of concussive impact.
visceral: Producing a bodily sensation of pressure or concussion.
sizzly: Emphasis of the frequency range above about 8kHz, which adds sibilance to all sounds, particularly those of cymbals and vocal esses (sibilants).
clinical: Sound that is pristinely clean but wholly uninvolving.
silvery: Sound that is slightly hard or steely, but clean.
steely: Shrill. Like “hard,” but more so.
hard: Tending toward steeliness, but not quite shrill. Often the result of a moderate frequency-response hump centered around 6kHz, sometimes also caused by small amounts of distortion.
closed-in: Lacking in openness, delicacy, air, and fine detail. A closed-in sound is usually caused by high-frequency roll-off above 10kHz. Compare with “open,” “airy.”
lean: Very slightly bass-shy. The effect of a very slight bass roll-off below around 500Hz. Not quite “cool.”
soft: Very closed-in, markedly deficient at the extreme high end.
opaque: Lacking detail and transparency.
pristine: Very clean-sounding, very transparent.
strident: Unpleasantly shrill, piercing.
shrill: Strident, steely.
silky: Pertains to treble performance that is velvety-smooth, delicate, and open.
screechy: The ultimate stridency, akin to chalk on a blackboard or a razor blade being scraped across a windowpane.
muddy: Ill-defined, congested.
tubby: Having an exaggerated deep-bass range.
vague, vagueness: Having poor specificity, confused.
velvet fog (as in “listening through a…”): Describes a galloping case of haze, wherein virtually all detail and focus are absent.

Listening to Sound

acuity: 1) The sensitivity of the ears to very soft sounds. 2) The acquired ability of an audiophile to hear and to assess the subtle qualitative attributes of reproduced sound.
audibility: The measure of the severity of a sonic imperfection. The scale of audibility, from least audible to most audible, is: inaudible, subtle, slight, moderate, obvious, conspicuous, and Arrggh!!
noticeable: In aural perception, any sonic quality which is clearly audible to most people.
perceptible: At or above the threshold of audibility of a trained listener.
subtle: Barely perceptible on a very good system. See “audibility.”
inaudible: A sonic imperfection which is either too subtle to be consciously perceived or is actually nonexistent. Compare “subliminal.”
subliminal: Too faint or too subtle to be consciously perceived. Compare “inaudible.” See “listening fatigue.”
slight: Easily audible on a good system but not necessarily on a lesser one. See “audibility.”
moderate: A qualifier which describes a sonic imperfection which is clearly audible through any decent system, but not annoyingly so. See “audibility.”
dramatic: Describing a perceived difference between components: very noticeable, unmistakable. A term misused by audio reviewers to demonstrate how incredibly sensitive they are to barely audible differences. See “audibility.”
observation: The perceived attribute of a sonic element, on which a personal judgment about its quality is based. Observations are described by subjective terms such as “smooth,” “woolly,” or “spacious.”
quality: The degree to which the reproduction of sound is judged to approach the goal of perfection.
involvement: The degree to which a reproduction draws the listener in to the musical performance and evokes an emotional response to it.
musical, musicality: A personal judgment as to the degree to which reproduced sound resembles live music. Real musical sound is both accurate and euphonic, consonant and dissonant.
phasey: A quality of reproduced sound which creates a sensation of pressure in the ears, unrelated to the intensity of the sound. Phasiness is experienced by many people when listening to two loudspeakers which are connected out of phase with each other.
cocktail party effect: The auditory system’s controllable ability to separate out, on the basis of direction alone, one sound source from many coming from different directions. This allows you to follow one voice among the others at a noisy cocktail party.
precedence effect: The tendency for the ears to identify the source of a sound as being in the direction from which it is first heard.
imagery: Descriptive terminology intended to convey an impression or mental image of a subjective observation. Imagery is usually employed to describe qualities in reproduced sound in terms of more familiar sensory responses like vision, taste, and touch.
articulation: 1) Clarity and intelligibility, usually of voice reproduction. 2) The reproduction of inner detail in complex sounds, which makes it easy to follow an individual musical voice among many.
palpable: Describes reproduction that is so realistic you feel you could reach out and touch the instruments or performers.
aliveness: A quality of sound reproduction which gives an impression that the performers are present, in person, in the listening room.

Components of Sound

characteristic: One of the basic properties of reproduced sound, which contributes to its perceived quality. Frequency response, loudness, extension, soundstaging, and resolution are sonic characteristics.
element: One of the constituent parts of a sonic characteristic. Bass, midrange, and treble are elements of frequency response. Depth and breadth are elements of soundstaging.
click: A small, sharp impulse that sounds like the word “click.”
impulse: An abrupt, extremely brief burst of signal energy; a transient.
crackle: Intermittent medium-sized clicks. The usual background noise from much-played vinyl discs.
buzz: A low-frequency sound having a spiky or fuzzy character.
attack: 1) The buildup of sound when an instrument is bowed, blown, struck, or plucked. 2) The ability of a system to reproduce the attack transients in musical sound. Poor attack makes a system sound slow.
attack transient: The initial energy pulse of a percussive sound, such as from a piano string, triangle, or drum head.
transient: See “attack transient.”
detail: The most subtle, delicate parts of the original sound, which are usually the first things lost by imperfect components. See “low-level detail.” Compare “haze,” “smearing,” “veiling.”
low-level detail: The subtlest elements of musical sound, which include the delicate details of instrumental sounds and the final tail of reverberation decay. See “delicacy.”
delicacy: The reproduction of very subtle, very faint details of musical sound, such as the fingertip-friction sounds produced when a guitar or a harp is played. See “low-level detail.”
sonic detail: See “detail.”
impulse noise: Transient noise, such as surface-noise ticks and pops.
noise: Any spurious background sounds, usually of a random or indeterminate pitch: hiss, crackles, ticks, pops, whooshes.
decay: The reverberant fadeout of a musical sound after it has ceased. Compare “attack.”

Frequency Range

Organized by ascending frequency.

frequency range: A range of frequencies stated without level limits: i.e., “The upper bass covers the frequency range 80–160Hz.”
frequency (or amplitude) response: 1) A range of frequencies stated with level limits: i.e., “The woofer’s response was 20–160Hz ±3dB.” 2) The uniformity with which a system or individual component sounds as if it reproduces the range of audible frequencies. Equal input levels at all frequencies should be reproduced by a system with subjectively equal output.
infrasonic: Below the range of audible frequencies. Although inaudible, the infrasonic range from 15–20Hz can be felt if strongly reproduced. Compare “subsonic.”
subsonic: Slower than the speed of sound through air. Often used incorrectly to mean “infrasonic.”
low frequency: Any frequency lower than 160Hz.
bass: The range of frequencies below 160Hz, characterized by low pitch.
sub-bass: Infrasonic bass.
deep bass: Frequencies below 40Hz.
low bass: The range from 20–40Hz.
midbass: The range of frequencies from 40–80Hz.
upper bass: The range of frequencies from 80–160Hz.
midrange (also “middles”): The range of frequencies from 160–1300Hz.
lower middles: The range of frequencies from 160–320Hz.
upper middles: The range of frequencies from 650–1300Hz.
high-frequency range: 1) The audio range above 1300Hz. 2) The usable upper limit of that range. See “extension.”
treble: The frequency range above 1.3kHz.
presence range: The lower-treble part of the audio spectrum, approximately 1–3kHz, which contributes to presence in reproduced sound.
lower highs: The range of frequencies from 1.3–2.6kHz.
middle highs: The range of frequencies from 2.6–5kHz.
upper highs: The range of frequencies from 10–20kHz.
top: The high treble, the range of audio frequencies above about 8kHz.
extreme highs: The range of audible frequencies above 10kHz.
ultrasonic: Beyond the upper-frequency limit of human hearing. Compare “supersonic.”
supersonic: Faster than the speed of sound through air. Sometimes used incorrectly to mean ultrasonic.
roll-off (also “rollout”): A frequency response which falls gradually above or below a certain frequency limit. By comparison, the term “cutoff” (often abbreviated to “cut,” as in “bass cut”) implies an abrupt loss of level above or below the frequency limit.

Coloration of Sound

vowel coloration: A form of midrange or low-treble coloration which impresses upon all program material a tonal “flavor” resembling a vowel in speech.
coloration: An audible “signature” with which a reproducing system imbues all signals passing through it.
neutral: Free from coloration.
“ah” (rhymes with “rah”): A vowel coloration caused by a frequency-response peak centered around 1000Hz.
honky: Pertaining to a severe “aw” coloration.
“aw” (rhymes with “paw”): A vowel coloration caused by a frequency-response peak centered around 450Hz. An “aw” coloration tends to emphasize and glamorize the sound of large brass instruments (trombone, tuba).
horn sound: An “aw” coloration characteristic of many loudspeakers that have a horn-loaded midrange.
comb filtering (also “flanging,” “phasing”): A hollow coloration that, once recognized, is unmistakable. Caused by a regularly spaced series of frequency-response peaks and dips, most often due to interference between two identical signals spaced in time. If that time difference is continually changed, the comb-filter peaks and dips move accordingly, giving rise to the familiar “phasing,” “flanging,” or “jet plane” effect used in modern rock music.
“ee” (rhymes with “we”): A vowel coloration caused by a frequency-response peak centered around 3.5kHz.
“eh” (as in “bed”): A vowel coloration caused by a frequency-response peak centered around 2kHz.
nasal: Reproduced sound having the quality of a person speaking with his/her nose blocked. Like the vowel “eh” coloration. In a loudspeaker, often due to a measured peak in the upper midrange followed by a complementary dip.
“ih” (as in “bit”): A vowel coloration caused by a frequency-response peak centered around 3.5kHz.
“oh” (as in “toe”): A vowel coloration caused by a broad frequency-response peak centered around 250Hz.
boxy: 1) Characterized by an “oh” vowel coloration, as when speaking with one’s head inside a box. 2) Used to describe the upper-bass/lower-midrange sound of a loudspeaker with excessive cabinet-wall resonances.
“oo” (as in “gloom”): A vowel coloration caused by a broad frequency-response peak centered around 120Hz.
hooty: 1) Pertaining to a severe “ooo” coloration. 2) Resonant colorations may cause some lower-midrange notes to jump forward or “hoot” at the listener.
pop: A midrange pulse characterized by a very sharp attack followed by a short “o” or “aw” vowel sound. Usually the result of a severe LP blemish.
pinched: 1) Very cold, with a “nyeah” coloration. 2) Pertaining to soundstaging: laterally compressed and lacking in spaciousness.
sibilance: A coloration that resembles or exaggerates the vocal s-sound.
soundstaging, soundstage presentation: The accuracy with which a reproducing system conveys audible information about the size, shape, and acoustical characteristics of the original recording space and the placement of the performers within it.
spitty: An edgy “ts” coloration which exaggerates musical overtones and sibilants as well as LP surface noise. Usually the result of a sharp response peak in the upper treble range.
wiry: Having an edgy or distorted high end, similar to the “tish” of brushed cymbals, but coloring all sounds reproduced by the system.
tizzy: A “zz” or “ff” coloration of the sound of cymbals and vocal sibilants, caused by a rising frequency response above 10kHz. Similar to “wiry,” but at a higher frequency.
cupped-hands: A coloration reminiscent of someone speaking through cupped hands or, if extreme, a megaphone.

Technical Attributes of Sound

definition: That quality of sound reproduction which enables the listener to distinguish between, and follow the melodic lines of, the individual voices or instruments comprising a large performing group.
resolution: See “definition.”
extension: The usable limits of a component’s frequency range.
reaction: A counterforce imparted to a speaker enclosure in response to the air resistance to the motion of a moving diaphragm or cone. On a thick carpet, a reacting enclosure will rock slightly back and forth, impairing low-frequency quality and overall detail.
dynamic range: 1) Pertaining to a signal: the ratio between the loudest and the quietest passages. 2) Pertaining to a component: the ratio between its no-signal noise and the loudest peak it will pass without distortion.
damping: The amount of control an amplifier seems to impose on a woofer. Underdamping causes loose, heavy bass; overdamping yields very tight but lean bass.
strained: Showing signs of audible distress during loud passages, as though the system is verging on overload. Compare “ease,” “effortless.”
ease: Pertains to reproduction which sounds effortless, free from strain.
effortless: Unstrained; showing no signs of audible stress during loud passages. Compare “strained.”
one-note bass: The exaggeration of a single bass note, due to a sharp low-frequency peak, normally due to an underdamped woofer but also caused by room resonances.
rotated: The sound of a frequency response that is linear but tilted.
monaural: Literally “hearing with one ear.” Often used incorrectly in place of “monophonic” (as in Glenn D. White’s otherwise excellent Audio Dictionary, 1991, second edition, University of Washington Press). Compare “binaural.”
binaural: Literally hearing with “two ears,” refers to a recording/playback system which presents the listener’s ears with the acoustic waveforms they would have received at the original event. Only currently achievable with a “dummy-head” microphone and playback via headphones.
mono (also “monophonic”): A system or recording with one channel or speaker. See “monaural.”
single-mono: Sound reproduction through a single loudspeaker system. Compare “dual mono.”
double (or dual) mono: Reproduction of a monophonic signal through both channels/speakers of a stereo system, as when a preamplifier’s mode switch is set to A+B (L+R). Compare “single mono.”
stereo (also “stereophonic”): A two-channel recording or reproducing system. Compare “binaural,” “monophonic.” See “dual mono,” “single mono.”
distortion: 1) Any unintentional or undesirable change in an audio signal.; 2) An overlay of spurious roughness, fuzziness, harshness, or stridency in reproduced sound.
rounding (also “rounding-off”): The shearing-off of sharp attack transients, due to poor transient response or restricted high-frequency range. See “slow,” “speed.”
dip: A narrow area of depression within an otherwise flat frequency-response curve.
suckout: A deep, narrow frequency-response dip.
scrape flutter: Roughness and veiling of analog tape sound due to discontinuous movement of the tape across the head (“violining”).
violining: See “scrape flutter.”
veiled, veiling: Pertaining to a deficiency of detail and focus, due to moderate amounts of distortion, treble-range restriction, or attack rounding.
smearing: Severe lack of detail and focus.
discontinuity: A change of tone color (timbre) or coloration due to the signal’s transition, in a multi-way speaker system, from one driver to another having dissimilar coloration.
slow: Sound reproduction which gives the impression that the system is lagging behind the electrical signals being fed to it. See “fast,” “speed,” “tracking.”
speed: The apparent rapidity with which a reproducing system responds to steep wavefronts and overall musical pace. See “fast,” “slow.”
tracking: The degree to which a component responds to the dictates of the audio signal, without lag or overshoot.
bright, brilliant: The most often misused terms in audio, these describe the degree to which reproduced sound has a hard, crisp edge to it. Brightness relates to the energy content in the 4kHz–8kHz band. It is not related to output in the extreme-high-frequency range. All live sound has brightness; it is a problem only when it is excessive.
crisp: In reproduced sound: sharply focused and detailed, sometimes excessively so because of a peak in the mid-treble region.
dirty: Sound reproduction which is fuzzy, cruddy, or spiky.
fast: Giving an impression of extremely rapid reaction time, which allows a reproducing system to “keep up with” the signal fed to it. (A “fast woofer” would seem to be an oxymoron, but this usage refers to a woofer tuning that does not boom, make the music sound “slow,” obscure musical phrasing, or lead to “one-note bass.”) Similar to “taut,” but referring to the entire audio-frequency range instead of just the bass.
quick: See “fast.”
flat: 1) Having a subjectively uniform frequency response, free from humps and dips. 2) Deficient in or lacking in soundstage depth, resulting in the impression that all reproduced sound sources are the same distance from the listener.
glare: An unpleasant quality of hardness or brightness, due to excessive low- or mid-treble energy.

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Acknowledgments

To our primary content editors, Carl Alviani and Kellyn Yvonne Standley, for long days and nights of in-depth help, and to the fantastic and very patient Angela Rufino and Mary Treseler, our editors at O’Reilly: thank you. Thank you to Lynn Kimbrough for copy editing.

Thanks also to our patient and dedicated content reviewers: Toby Nelson, Jonathan H Brown, Nim Wunnan, James Nesfield, Joshua Marinacci, Xuehong Liu, Peter Sikking, Karen Kaushansky, Jess Mitchell, Alexander Baumgardt, Peter Bautista, Martyn Rowe, Dennis DeSantis, George Abraham, and Anselm Hook.

Amber Case would like to thank Toby Nelson for always believing in her, no matter the odds. She would like to thank her mom for giving her an early desire to learn; Sheldon Renan, for getting her to write books in the first place; Douglas Rushkoff, for his positive and constant encouragement; and Professor Deborah Heath, for getting her started in the field of studying humans and technology. Finally, she would like to thank her late father, Eliot Case, who passed away from cancer during the production of this book. He was a recording engineer, sound designer, and inventor. Her childhood memories of her father were filled with speakers, microphones, and synthesizers. She watched him constantly experiment with sounds and spaces. Although he did not live to see the final production of this book, it is her hope that it might make him proud.

Aaron Day would like to thank his wife, Cornelia, and son, Avo, for their encouragement and patience throughout this process. He would also like to thank Jim Flynn, Vance Galloway, and Bruce Christian Bennett for their wisdom, which started him on this path so long ago.

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Designing with Sound by Amber Case, Aaron Day