ACTIVE ACOUSTIC ATTENUATOR

摘要

An active acoustic attenuator is provided by the subject invention for the attenuation of a relatively broad band of lower frequency sound from a given source propagating through a confined enclosure such as a duct, by the introduction of cancelling sound having the mirror image amplitude and phase characteristics of the source sound. The active acoustic attenuator herein includes a speaker disposed at a remote location from the duct which is connected thereto by a waveguide. The speaker is driven by electronic circuitry including an adaptive filter having a modified LMS algorithm governing the operation of its transversal filter which accommodates the inherent delays associated with the propagation of acoustic waves in a duct.