Electronic Sound Absorber

Abstract

The electronic sound absorber is so named because it absorbs sound or reduces the sound level by means of an electronic transducing system as contrasted to conventional sound absorption by direct conversion from acoustical to heat energy. The electronic sound absorber consists of a microphone, amplifier, and loudspeaker connected so that for an incident sound wave the sound pressure at the microphone is reduced. Thus it will be seen that electronic sound absorber is a feedback system which operates to reduce the sound pressure in the vicinity of the microphone. The sound pressure in the neighborhood of the microphone can be reduced 10 to 25 decibels over a frequency range of three octaves in the low frequency portion of the audiorange. The electronic sound absorber may be used to reduce the noise over a small volume, that is, spot type noise reducer, or it may be used with an acoustical resistance to obtain a high order of sound absorption in the low frequency range.