Sound

thumb|A drum produces sound via a vibrating membrane.

thumb|thumbtime=23|Video showing how sounds make their way from the source to the brain|upright=1.35 Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science.

thumb|alt=Lindsay's Wheel of acoustics|upright=1.75|Lindsay's Wheel of Acoustics, which shows fields within acoustics

frequency change of a wave for observer relative to its source

distance travelled during a unit of time by a sound wave propagating through an elastic medium

change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated

thumb|right|upright=1.35|Barbershop quartets, such as this US Navy Band ensemble, sing four-part pieces, made up of a [[melody line (normally the lead) and three harmony parts. ]] In music, harmony is the concept of combining different sounds in order to create new, distinct musical ideas. Theories of harmony seek to describe or explain the effects created by distinct pitches or tones coinciding with one another; harmonic objects such as chords, textures and tonalities are identified, defined, and categorized in the development of these theories. Harmony is broadly understood to involve both a

thumb|right|An ultrasonic examination

thumb|Saint Anne, Coptic [[tempera plaster wall painting from the 8th century]] thumb|Keep silent sign in South Africa.

The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the variable's extreme values. In older texts, the phase of a periodic function is sometimes called the amplitude.

device used to produce a fixed tone

thumb|right|Spectrogram of the first second of an E9 [[suspended chord played on a Fender Stratocaster guitar. Below is the E9 suspended chord audio: File:9577 Guitarz1970 Clean E9 Guitar Chord (Mike Tribulas).ogg ]]

mathematical curve that describes a smooth repetitive oscillation; continuous wave

physical system that responds to a restoring force inversely proportional to displacement

speed that exceeds the speed of sound

thumb|upright=1.5|Infrasound arrays at a monitoring station in Qaanaaq, [[Greenland]]

perceptual property in music ordering sounds from low to high

thumb|384x384px|Reverb on a guitar

random signal having equal intensity at different frequencies, giving it a constant power spectral density

instantaneous product of sound pressure and particle velocity

obstacle to achieving supersonic speed

sound associated with shock waves created when an object travels through the air faster than the speed of sound

science and engineering of achieving a good sound within a building

high-quality reproduction of sound

measure comparing the level of a searched signal to the level of background noise

local pressure deviation from the ambient atmospheric pressure, caused by a sound wave

thumb|250px|The node (physics)|nodes of a vibrating string are harmonics. thumb|Two different notations of natural harmonics on the cello. First as sounded (more common), then as fingered (easier to sightread).

filter that passes signals with a frequency lower than a certain cutoff frequency, and attenuates signals with higher frequencies

term in acoustics

upright=1.35|thumb|A pair of headphones being tested inside an [[anechoic chamber for soundproofing]]

type of signal whose amplitude is inversely proportional to its frequency

exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution

sound intended to be heard as if it were emanating from one position

thumb|Spectrograms of [[Thrush nightingale (Luscinia luscinia) and Common nightingale (Luscinia megarhynchos) singing help to reliably distinguish these two species by voice.]] Bioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually, it refers to the investigation of sound production, dispersion and reception in animals (including humans). This involves neurophysiological and anatomical basis of sound production and detection, and relation of acoustic signals to the medium they disperse through. The findings provide clues about the evolution of acoustic mechan

quotient of average sound pressure at a surface and sound volume flow rate through that surface

device for acoustic measurements

A soundscape is the acoustic environment as perceived by humans, in context. The term, originally coined by Michael Southworth, was popularized by R. Murray Schafer. There is a varied history of the use of soundscape depending on discipline, ranging from urban design to wildlife ecology to computer science. An important distinction is to separate soundscape from the broader acoustic environment. The acoustic environment is the combination of all the acoustic resources, natural and artificial, within a given area as modified by the environment. The International Organization for Standardization

Phonophobia, also called ligyrophobia or sonophobia, is a fear of or aversion to specific sounds—a type of specific phobia as well as a form of auditory hypersensitivity. Occasionally it is called acousticophobia. Although some sounds could be feared by most people, such as certain loud sounds or sounds that signal threats, fears of these sounds would not be considered phonophobia unless the amount of fear and anxiety was disproportionate. In phonophobia, the feared sounds may be ones that are soft and non-damaging, such as kitchen sounds or a door closing. Another example is watching someone

frequency selection subsystem for various receiver systems

longitudinal wave that propagates by means of adiabatic compression and decompression;travels with the speed of sound which depends on the medium they're passing through

Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mechanism is typically that of one structure with a well-defined lip, ridge, or nodules (the "scraper" or plectrum) being moved across a finely-ridged surface (the "file" or stridulitrum—sometimes called the pars stridens) or vice versa, and vibrating as it does so, like the dragging of a phonograph needle across a vinyl record. Sometimes it is the structur

thumb|upright=1.3|right|Equal-loudness contours The phon is a logarithmic unit of loudness level for tones and complex sounds. Loudness is measured in sones, a linear unit. Human sensitivity to sound is variable across different frequencies, so although two different tones may present an identical sound pressure to a human ear, they may be psychoacoustically perceived as differing in loudness. The purpose of the phon is to provide a logarithmic measurement (like decibels) for perceived sound magnitude, while the primary loudness standard methods result in a linear representation. A sound with

biological process to identify the location or origin of a detected sound in direction and distance

Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks. In the 1980s, broadcasters began to use NICAM compression for transmissions of stereo TV sound to the public.

periodic vibration whose frequency is audible to the average human

perception of being physically present in a non-physical world

sound with a sinusoidal waveform

Growling is a low, guttural vocalization produced by animals as an aggressive warning but can also be found in other contexts such as playful behaviors or mating. Different animals will use growling in specific contexts as a form of communication. In humans, low or dull rumbling noises may also be emitted when they are discontent with something or they are angry, although this human sound is often termed "groaning" & "grunting".

surface integral over the sound intensity

AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code-modulated digital audio over several transmission media including balanced lines, unbalanced lines, and optical fiber.

study of the propagation of sound in water and the interaction of sound waves with the water and its boundaries

branch of engineering dealing with sound and vibration

difference between phase angles

audio or video represented as a stream of discrete numbers

REDIRECT Underwater acoustics

point along a standing wave where the wave has minimum amplitude

A vibration in a string is a wave

strategies to reduce noise pollution or its impact

frequency characteristics of hearing and perceived volume

device in communications engineering