Attenuation of sound waves

摘要

An active sound control system is described in which allowance is made in a relatively uncomplicated circuit for acoustic coupling between a sound generating system for generating a cancelling sound wave and a detector for sensing a sound wave to be cancelled. Unwanted sound from a source is detected by a microphone and cancelled by sound from a speaker connected by way of an amplifier to the microphone. The amplifier has a feedback processing system with a transfer function which takes account of acoustic feedback between the speaker and the microphone in deriving, with the amplifier, a signal to drive the speaker.