Reducing the Integral Noise Level of Active Speech Protection Facilities by Switching Frequency Bands

摘要

This article is devoted to experimental review of idea, which offers to generate noise in alternate frequency bands in order to reduce the integral noise level of active speech protection facilities. The idea is that at any given moment of time acoustic noise should exist not in a full range of frequencies, but only in a certain number of bands, and this set of bands changes with a specified period. During the study, a number of patterns was identified. First of all, it was found that the best way to divide the full range of frequencies for this idea is to use bands of equal length. In particular, the dependence was identified - the smaller length of the bands is used, the more effective noise in terms of formant intelligibility can be created. The alternation period of bands should be smaller than the minimal duration of the speech sounds. The best result was obtained with a low-frequency distribution, when the bands from the low-frequency range are used more often than the bands from the high-frequency range. This effect is explained by asymmetric influence of noise on perception of sounds. As a result, a gain (decrease) in the integral level of 6.2 dB was achieved comparing with white noise (7 octave bands).