ELECTRO-ACOUSTIC or ELECTROACOUSTIC
An adjective describing any process involving the transfer of a SIGNAL from acoustic to electrical form, or vice versa. Most commonly, TRANSDUCERs such as the MICROPHONE or LOUDSPEAKER are examples of this process. Compare: AUDIO.
Although the term most precisely refers to a signal transfer from electrical to acoustic form or vice versa, it also is often used more loosely to refer to any process for the electronic generation and/or manipulation of sound signals, including techniques of SOUND SYNTHESIS for the electronic or digital generation of such signals. When the purpose of such manipulation is artistic, the result is commonly called electroacoustic music.
See also: DIFFUSION, ELECTRONIC MUSIC, MOOZAK, MUSIQUE CONCRETE, SOUND OBJECT, STEREOPHONIC.
A large number of sounds commonly heard in the contemporary environment are electroacoustic in origin, ranging from HUMs and flat line sounds (see STATIONARY SOUND), through electrically driven devices, to the electroacoustic reproduction of sound via the TAPE RECORDER, phonograph record or compact disc, radio, television, telephone, film track, etc. As a result, it is now often claimed that the most universal acoustic instrument is the LOUDSPEAKER.
Electrification of sounds previously powered by other means will change their character, including waveform, timbre, duration, intensity and envelope characteristics. For instance, the ability to SWITCH an electronic siren on and off abruptly produces a faster and more startling ATTACK, a brief DECAY (contrasting sharply with the prolonged decay of mechanical sirens), higher intensities, and patterns of modulation, called the 'wail' and 'yelp' modes, that were previously impossible to obtain. See also: DISAPPEARING SOUND.
Each stage of an electroacoustic COMMUNICATION chain introduces a certain distortion, as well as NOISE, into the system. For instance, the DIRECTIVITY and FREQUENCY RESPONSE patterns of microphones and loudspeakers influence the way in which a sound is recorded or reproduced. The limited DYNAMIC RANGE of electroacoustic systems, compared to that of the ear or the original sound or environment, requires techniques of signal compression (note the further use of this technique in radio as described under COMPRESSION). Compare: FIDELITY.
More subtly, the split between the original sound and its electroacoustic reproduction, which has been termed SCHIZOPHONIA, changes the way in which the sound will be heard by the listener. Sounds may appear in unusual or inappropriate settings (e.g. orchestral music in elevators) and may thereby contribute to SOUND POLLUTION; sounds may be exact repetitions more often than they are unique occurrences; sounds may occur at intensities, durations, densities and speeds never before experienced, as well as in succession or simultaneity with other sounds to an arbitrary degree of complexity. All of these new possibilities can change a listener's habits or modes of listening, particularly through frequent exposure; some changes may dull, others stimulate, listening attitudes and abilities.
Sound Example: Milking a cow by hand, followed by the electrical equivalent.Sound Example: Three foghorns at Point Atkinson, West Vancouver, B.C., the last of which is electronic.
Sound Example: Fluorescent light hum.
Sound Example: Amplified voice from a mobile public address system.
Sound Example: Background music in a shopping mall.