A glossary of disciplines and applications.
by Dave Skipper

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Oh noise, how may I study thee? Let me count the ways…

This is more of a reference article for my own benefit, and is not necessarily for trawling through line by line, though I think it’s quite interesting to do that! I wanted to compile in one place a cross-section of fields, applications, phenomena, and definitions that involve (in varying degrees) the study of some form of noise or sound or music. I thought this would be interesting and useful for having a wider awareness of what is being pursued academically and practically around sound and noise. I decided to organise the list alphabetically rather than taxonomically (by category). Inevitably there are gaps and overlaps – there is no one way to arrange such a list, and this attempt is far from perfect.

As my writing continues into the future, some of these areas will demand further engagement and research according to the focus of the particular topic at hand. I will refer to or dip into other areas along the way as appropriate. Links, and most of the definitions, are taken from Wikipedia. Feel free to comment below or email me [ reppiks (at) gmail (dot) com ] with anything you think I ought to add to this list.

[For my other references articles, see Definitely Noise (noise definitions) and Classified Noise (noise categories).]

A

• Acousmatic sound – sound that is heard without an originating cause being seen.
• Acoustics – the branch of physics that deals with the study of all mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound.
• Acoustic absorption – the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy.
• Acoustic attenuation – a measure of the energy loss of sound propagation in media.
• Acoustic dispersion – the phenomenon of a sound wave separating into its component frequencies as it passes through a material.
• Acoustic ecology – a discipline studying the relationship, mediated through sound, between human beings and their environment; sometimes called ecoacoustics or soundscape studies.
• Acoustic emission – the phenomenon of radiation of acoustic (elastic) waves in solids that occurs when a material undergoes irreversible changes in its internal structure, for example as a result of crack formation or plastic deformation due to aging, temperature gradients or external mechanical forces.
• Acoustic engineering – the branch of engineering dealing with sound and vibration. It is the application of acoustics, the science of sound and vibration, in technology.
• Acoustic fingerprint – a condensed digital summary, a fingerprint, deterministically generated from an audio signal, that can be used to identify an audio sample or quickly locate similar items in an audio database.
• Acoustic levitation – a method for suspending matter in a medium by using acoustic radiation pressure from intense sound waves in the medium. Also acoustophoresis.
• Acoustic location – the use of sound to determine the distance and direction of its source or reflector.
• Acoustic metamaterial – a material designed to control, direct, and manipulate sound waves as these might occur in gases, liquids, and solids.
• Acoustic microscopy – the technique of using sound waves to visualize structures too small to be resolved by the human eye.
• Acoustic quieting – the process of making machinery quieter by damping vibrations to prevent them from reaching the observer.
• Acoustic resonance – a phenomenon where acoustic systems amplify sound waves whose frequency matches one of its own natural frequencies of vibration (its resonance frequencies).
• Acoustic signal processing – a subfield of signal processing that is concerned with the electronic manipulation of both digital and analogue audio signals.
• Acoustic signature – the combination of acoustic emissions of sound emitters (such as vehicles, machinery, and living animals), which can be used to study their condition, behaviour, and physical location.
• Acoustic theory – a scientific field, deriving from fluid dynamics, that relates to the description of sound waves.
• Acoustic transmission – the transmission of sounds through and between materials, including air, wall, and musical instruments.
• Acousto-optics – a branch of physics that studies the interactions between sound waves and light waves, especially the diffraction of laser light by ultrasound (or sound in general) through an ultrasonic grating.
• Aeroacoustics – the study of noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces.
• Ambisonics – a full-sphere surround sound format: in addition to the horizontal plane, it covers sound sources above and below the listener.
• Anthropophony – the study of all sounds produced by humans, whether coherent, such as music, theatre, and language, or incoherent and chaotic such as random signals generated primarily by electromechanical means.
• Archaeoacoustics – the use of acoustical study as a methodological approach within the field of archaeology. Archaeoacoustics examines the acoustics of archaeological sites and artifacts.
• Architectural acoustics – the science and engineering of achieving a good sound within a building; also known as room acoustics and building acoustics.
• Asteroseismology – the study of oscillations in stars, which can be frequency shifted into audible sound (also astroseismology, helioseismology, stellar seismology)
• Atmospheric noise – radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms.
• Audio analysis – the extraction of information and meaning from audio signals for analysis, classification, storage, retrieval, synthesis, etc.
• Audio engineering – the production of a recording or a live performance (typically of music and/or speech), balancing and adjusting sound sources using equalization and audio effects, mixing, reproduction, and reinforcement of sound; also called sound engineering and recording engineering.
• Audio system measurements – Designers take measurements so that they can specify the performance of a piece of equipment. Maintenance engineers make them to ensure equipment is still working to specification, or to ensure that the cumulative defects of an audio path are within limits considered acceptable.
• Audiometry – a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies.
• Audiology – a branch of science that studies hearing, balance, and related disorders.

B

• Background noise or ambient noise – any sound other than the sound being monitored (primary sound).
• Baryon acoustic oscillations – (cosmology) fluctuations in the density of the visible baryonic matter (normal matter) of the universe, caused by acoustic density waves in the primordial plasma of the early universe. I
• Bioacoustics – the investigation of sound production, dispersion and reception in animals (including humans), involving the neurophysiological and anatomical basis of sound production and detection, and relation of acoustic signals to the medium they disperse through.
• Biophony – the collective impact of all sounds emanating from natural biological origins in a given habitat. The realm of study is focused on the intricate relationships – competitive and/or cooperative – generally between non-human biological sound sources taking into account seasonal variability, weather, and time of day or night, and climate change.

C

• Colours of noise – the power spectrum of a noise signal (a signal produced by a stochastic process), for example white noise, grey noise, black noise, pink noise, red/brown/Brownian noise, Gaussian noise.
• Communication noise – influences on effective communication and interpretation;  includes psychological noise, environmental noise, physical noise, physiological noise, and semantic noise.
• Cosmic noise and galactic radio noise – random noise that originates outside the Earth’s atmosphere.
• Cymatics – a subset of modal vibrational phenomena, sometimes utilised for physical/visual representation of sound/music.
  

E

• Electroacoustics – a branch of acoustic engineering that deals with the design of headphones, microphones, loudspeakers, sound systems, sound reproduction and recording.
• Electronic noise – in electronics, noise is an unwanted disturbance in an electrical signal; in communication systems, noise is an error or undesired random disturbance of a useful information signal.
• Environmental noise – the summary of noise pollution from outside, caused by transport, industrial and recreational activities. See also noise measurement.
• Ethnomusicology – the study of music from the cultural and social aspects of the people who make it.
• Euphony and cacophony – Euphony is the effect of sounds being perceived as pleasant, rhythmical, lyrical, or harmonious. Cacophony is the effect of sounds being perceived as harsh, unpleasant, chaotic, and often discordant; these sounds are perhaps meaningless and jumbled together.

F

• Fisheries acoustics – a range of research and practical application topics using acoustical devices as sensors in aquatic environments.
• Free field (acoustics) – a situation in which no sound reflections occur.

G

• Geoacoustics – a branch of acoustics in which sonic, infrasonic, and ultrasonic phenomena occurring in the earth’s crust are studied.
• Geometrical acoustics – a branch of acoustics that studies propagation of sound on the basis of the concept of rays considered as lines along which the acoustic energy is transported. Also called ray acoustics.
• Geophony – the study of the components of the soundscape that relate to the naturally occurring non-biological audio signal sources coming from different types of habitats, whether marine or terrestrial.

H

• Health effects from noise – the physical and psychological health consequences of regular exposure, to consistent elevated sound levels (for example tinnitus, the hearing of sound when no external sound is present).
• Hydroacoustics – the study and application of sound in water.

I

• Image noise – random variation of brightness or color information in images, and is usually an aspect of electronic noise.
• Information theory – the study of the quantification, storage, and communication of information.
• Infrasonics – the study of infrasound, sound that is lower in frequency than 20 Hz or cycles per second, the “normal” limit of human hearing.

L

• Loudspeaker acoustics – a subfield of acoustical engineering concerned with the reproduction of sound and the parameters involved in doing so in actual equipment.

M

• Medical ultrasonography – a diagnostic imaging technique based on the application of ultrasound, used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal organs. Its aim is often to find a source of a disease or to exclude pathology. Also called diagnostic sonography or medical sonography..
• Meteorological acoustics – the science of the sounds of meteorological (weather) phenomena.
• Music archaeology – an interdisciplinary study field that combines musicology and archaeology.
• Music history – the highly diverse subfield of the broader discipline of musicology that studies music from a historical viewpoint; sometimes called historical musicology.
• Music information retrieval – the interdisciplinary science of retrieving information from music. Also known as musical audio mining.
• Music instrument technology – the construction of instruments and the way they have changed over time.
• Music psychology – a branch of both psychology and musicology that aims to explain and understand musical behaviour and experience, including the processes through which music is perceived, created, responded to, and incorporated into everyday life.
• Music theory, analysis and composition – a field of study that describes the elements of music and includes the development and application of methods for composing and for analyzing music through both notation and, on occasion, musical sound itself.
• Music therapy – the use of music to improve health or functional outcomes. Music therapy is a creative arts therapy, consisting of a process in which a music therapist uses music and all of its facets—physical, emotional, mental, social, aesthetic, and spiritual—to help clients improve their physical and mental health.
• Musical acoustics – a branch of acoustics concerned with researching and describing the physics of music – how sounds are employed to make music. Examples of areas of study are the function of musical instruments, the human voice (the physics of speech and singing), computer analysis of melody, and in the clinical use of music in music therapy.
• Musicology – the scholarly analysis and research-based study of music.

N

• Neoacoustics – the study of new sounds. Actually I made this one up ‘cos it sounds cool… and congratulations if you’re actually reading right through and got this far!
• Noise as metaphor – separate (though not unrelated) to audio noise or visual/computational/mathematical noise, this is the concept of noise utilised as an analogy or descriptor of other phenomena whether physical/social/emotional/philosophical/etc. For example, noise as a metaphor of destructive or degenerative processes in the natural world, in relationships, or in the mind: disharmony, disease, decay, death, disappointment, disorientation, discord, depression, disaster, and so on.
• Noise control – a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors; also called noise mitigation.
• Noise floor – the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored.
• Noise generators – electrical circuits that produces electrical noise (i.e., a random signal).
• Noise health effects – the physical and psychological health consequences of regular exposure, to consistent elevated sound levels.
• Noise in music – the use of unpitched, indeterminate, uncontrolled, loud, unmusical, or unwanted sounds in music. (Especially history, characters, culture, recordings, performances, etc within experimental music, noise music, musique concrète, improvised music, electronic music, industrial music, sound art, performance art, the avant-garde, etc.)
• Noise pollution – the propagation of noise with harmful impact on the activity of human or animal life; also known as environmental noise or sound pollution.
• Noise regulation – includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government.
• Noise, vibration, and harshness (NVH) – the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks; also known as noise and vibration (N&V).
• Nonlinear acoustics – a branch of physics and acoustics dealing with sound waves of sufficiently large amplitudes.

O

• Occupational noise or industrial noise – the amount of acoustic energy received by an employee’s auditory system when they are working in the industry.
• Onomatopoeia –  the process of creating a word that phonetically imitates, resembles, or suggests the sound that it describes.
• Optoacoustics or photoacoustics – the study and application of the formation of sound waves following light absorption in a material sample.
• Organology – the science of musical instruments and their classification.
• Otology – a branch of medicine which studies normal and pathological anatomy and physiology of the ear (hearing and vestibular sensory systems and related structures and functions) as well as their diseases, diagnosis and treatment.

P

• Passive acoustics – the action of listening for sounds, often at specific frequencies or for purposes of specific analyses.
• Phonetics – a branch of linguistics that studies the sounds of human speech, or—in the case of sign languages—the equivalent aspects of sign. It is concerned with the physical properties of speech sounds or signs (phones): their physiological production, acoustic properties, auditory perception, and neurophysiological status.
• Phonphobia or ligryophobia or sonophonia or acousticophobia –  a fear of or aversion to loud sounds. See also astraphobia (the fear of thunder and lightning, also called astrapophobia, brontophobia, keraunophobia, or tonitrophobia) and misophonia (literally ‘hatred of sound’).
• Phonosemantics or sound symbolism or phonoaesthesia – the idea that vocal sounds or phonemes carry meaning in and of themselves; studying archetypal relationships between sounds and ideas.
• Physical acoustics – the area of acoustics and physics that studies interactions of acoustic waves with a gaseous, liquid or solid medium on macro- and micro-levels.
• Popular music studies – writing about popular musics past and present.
• Pseudorandom noise – in cryptography, a signal similar to noise which satisfies one or more of the standard tests for statistical randomness.
• Psychoacoustics – the scientific study of sound perception and audiology – how humans perceive various sounds. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound (including noise, speech and music).

Q

• Quantum acoustics – the study of sound under conditions such that quantum mechanical effects are relevant.

S

• Seismology – the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. See also astroseismology, helioseismology, lunar seismology.
• Signal processing – a subfield of mathematics, information and electrical engineering that concerns the analysis, synthesis, and modification of signals.
• Sonar – a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.
• Sonic boom – the sound associated with the shock waves created whenever an object travelling through the air travels faster than the speed of sound.
• Sonic weaponry – weapons of various types that use sound to injure, incapacitate, or kill an opponent.
• Sonics – the science and technology of sound.
• Sonification – the act of applying sound energy to agitate particles in a sample, for various purposes such as the extraction of multiple compounds from plants, microalgae and seaweeds.
• Sonochemistry – is concerned with understanding the effect of ultrasound in forming acoustic cavitation in liquids, resulting in the initiation or enhancement of the chemical activity in the solution.
• Sonoluminescence – the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.
• Sound art – an artistic discipline in which sound is utilised as a primary medium.
• Sound mimesis – the imitation of natural sounds, e.g. for Shamanic rituals, entertainment, or luring animals.
• Sound recording and reproduction – an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects.
• Sound studies – an interdisciplinary field that to date has focused largely on the emergence of the concept of “sound” in Western modernity, with an emphasis on the development of sound reproduction technologies.
• Sound synthesis – various methods of sound generation in audio electronics.
• Soundproofing – any means of reducing the sound pressure with respect to a specified sound source and receptor. See also noise barrier.
• Soundscape ecology – the study of the acoustic relationships between living organisms, human and other, and their environment, whether the organisms are marine or terrestrial.
• Spectral noise – random or unwanted signals appear in many fields including in acoustics (e.g. aircraft noise, jet noise, traffic noise, roadway noise, train noise, background noise, grey noise, industrial noise), biology (e.g. cellular noise, developmental noise, neuronal noise, synaptic noise, transcriptional noise), computer graphics (e.g. gradient noise, Perlin noise, Simplex noise, simulation noise, value noise, wavelet noise, Worley  noise), electronics and radio (e.g. burst noise, ground noise, atmospheric noise, comfort noise, cosmic noise, video noise, radio noise, shot noise), mathematics (e.g. colours of noise, pseudorandom noise, statistical noise, noise-based logic, noise print), and other (e.g. electrochemical noise, phonon noise, seismic noise).
• Spectromorphology – the perceived sonic footprint of a sound spectrum as it manifests in time.
• Spectroscopy – the study of the interaction between matter and radiative energy, predominantly in the electromagnetic spectrum, though matter waves and acoustic waves can also be considered forms of radiative energy.
• Structural acoustics – the study of the mechanical waves in structures and how they interact with and radiate into adjacent media.
• Supersonic fracture –  fractures where the fracture propagation velocity is higher than the speed of sound in the material.
• Supersonic speed – the rate of travel of an object that exceeds the speed of sound.

T

• Theoacoustics – God-sounds, or theology of sound.
• Theory of sonics – a branch of continuum mechanics which describes the transmission of mechanical energy through vibrations.
• Therapeutic ultrasound – any type of ultrasonic procedure that uses ultrasound for therapeutic benefit.
• Thermal noise – the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage.
• Thermoacoustics – the interaction between temperature, density and pressure variations of acoustic waves.

U

• Ultrasonics – the study of  sound waves with frequencies higher than the upper audible limit of human hearing.
• Underwater acoustics – the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water, its contents and its boundaries.

V

• Vibration and dynamics – acoustic engineers working on vibration study the motions and interactions of mechanical systems with their environments, including measurement, analysis and control.

W

• Waveguide – a physical structure for guiding sound waves.

 

DEPARTMENT PAGE FOR THIS SERIES: THE WORD ON NOISE
PREVIOUS ARTICLE IN THIS SERIES: Thinking About Noise
NEXT ARTICLE IN THIS SERIES: My Ears Are Ravenous