Pyschoacoustical comparison of active versus passive noise control techniques

Abstract

Comparisons of active versus passive noise control techniques can be found in various papers. However, this comparison mainly concerns economic, operational, or technical considerations. The present contribution aims at describing the psychoacoustical effects produced by some of the classical solutions used in passive and active noise control. The models introduced by Zwicker and his coworkers, and by Moore and Glasberg are used to evaluate the auditory efficiency of passive and active noise control techniques. Several types of signals were examined: (i) test signals obtained with a band of noise embedded in a white noise or a pink noise; (ii) actual environmental noises: noise produced by the turbine of an aircraft or by a car engine, and several interior noises (locomotive, helicopter and car). It is shown that the modifications in the spectrum of a signal that can be produced by active control are sometimes disappointing, because they induce a subjective enhancement of the high-frequency portion of the spectrum. What the listener then commonly reports is that overall the signal has become slightly softer, but also more unpleasant. The use of a hybrid noise control technique, combining active and passive control, can greatly reduce this effect.