Noise

a sound in which tonality is absent or implicitly expressed. Known varieties of noise: white noise (Johnson noise) – has a spectrum with approximately constant spectral density over its entire length; pink noise – its spectrum has a spectral density decreasing by 3 dB with each subsequent octave (spectral density is inversely proportional to the frequency); orange noise is a quasi-constant noise with a finite spectral density, the spectrum of such noise has strips of zero energy scattered throughout its length, such strips are located near the frequencies corresponding to musical notes; green noise – similar to pink noise with an amplified frequency range in the region of 500 Hz; blue noise– its spectral density increases by 3 dB with each subsequent octave (spectral density is proportional to frequency); purple noise – differentiated white noise, its spectral density increases by 6 dB with each subsequent octave (spectral density is proportional to the square of the frequency); gray noise – the spectrum of such noise has a graph similar to the graph of the psychoacoustic curve of the threshold of audibility, which means that for a person’s hearing aid this noise has the same volume over the entire audible frequency range; brown noise – its spectral density decreases by 6 dB with each subsequent octave (spectral density is inversely proportional to the square of the frequency); black noise– there are a lot of definitions of this noise, one of them: black noise is supersonic white noise, such noise has a constant finite spectral density beyond the threshold of audibility (20 KHz). Broadband noise is noise whose energy is distributed over a wide frequency range (more than one octave).

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