Possibility of reducing reverberation time by negative electroacoustic feedback

Abstract

Although electroacoustic feedback channels have been very sucessfully used with positive feedback to increase reverberation times, the reduction of reverberation time by negative feedback has had only very limited experimental success. As part of a thorough investigation of tone-burst responses of electroacoustic feedback channels, the possibility of reverberation reduction was closely examined. Both computed results and measurements in a three-dimensional model showed that the resulting reverberation times were not accurately predicated by the normal feedback equations. The results were dependent on the reflection coefficient of the enclosure and the length of the source tone-burst, as well as the channel loop gain. In contradiction of other recent results, reverberation reduction by this method was not found to be of great practical utility, as in many cases the reverberation time was increased rather than decreased.