Technology / Home Audio / Noise: Perceived sounds not in the original soundtrack. Such things as hiss, crackle, pops, hum, and buzz, are typical of the types of extraneous signals described as noise. Inherent noise in the electronic processing in any sytem is measured in decibels relative to the amplitude of the original signal. Sounds perceived as noise are heard in contrast to the sound that is the object of attention. Thus, a noise signal measured at 15 decibels below the output of Tchaikovski's 1812 Overture finale would probably not even be heard; while a slight hiss at 55 db below the level of a soft piano passage would be annoyingly obvious. Generally, any piece of equipment which generates ambient noise of more than 90 db below the level of a typical audio signal is noise free as far as most human perception is concerned.
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Other Words for Noise

Noise Noun Synonyms: sound, clamour, crash, clap, clash, clangour, din, thunder, thundering, rumble, rumbling, outcry, hubbub, uproar, hullabaloo, racket, charivari or and also shivaree, rattle, caterwauling, rumpus, blare, blast, blasting, bawling, babel
Noise Adjective Synonyms: sound, disturbance

Dolby Noise Reduction

Technology / Home Audio / Dolby Noise Reduction: Decodes Dolby-encoded cassette tapes during playback to virtually eliminate the tape hiss which is especially apparent in quiet environments. Dolby B is the most widely used system. Dolby C is an exte MORE

Signal-To-Noise Ratio

Science / Spiders / Signal-To-Noise Ratio: ratio of signal variance to noise variance, computed for a given band limit. MORE

Spectral Signal-To-Noise Ratio (SSNR)

Science / Spiders / Spectral Signal-To-Noise Ratio (SSNR): measure of resolution proposed by Michael Unser and coworkers [Unser et al., 1987] [119-121]. MORE