Fluctuation strength

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The fluctuation strength is a measure of the subjectively perceived fluctuation in volume .

The unit of measure of fluctuation is vacil . 1 vacil is defined as the fluctuation strength of a 1 kHz tone of 60  dB sound pressure , which is amplitude modulated with a frequency of 4  Hz and a degree of modulation of 1.0 = 100% . The modulation frequency of the noise must be determined with a high degree of accuracy, which means that signal lengths of at least 4 seconds are necessary.

The strength of the fluctuation is proportionally scaled , i.e. H. a noise that is perceived to fluctuate twice as much as the definition sound has a fluctuation strength of 2 vacil.

Eberhard Zwicker and Hugo Fastl provided the model for calculating the degree of fluctuation . The fluctuation strength is one of the Zwicker parameters , such as


  1. Eberhard Zwicker, Hugo Fastl: Psychoacoustics. Facts and Models (Springer Series in information sciences; 22). Springer, Berlin 1990, ISBN 3-540-52600-5 .