Active control of harmonic and random sound transmission in a structural-acoustic system

Abstract

The active control of sound transmission in structural-acoustic coupled systems has been of interest in recent years. Two particular problems that have received attention are the active control of harmonic sound transmission into aircraft, and control of random noise transmission into the payload bay of space rockets. This paper describes an analytical and experimental investigation to compare the feedforward control of harmonic and random sound transmission into an acoustic cavity. A rectangular enclosure is considered that has five acoustically rigid walls and a flexible plate on the remaining side through which a plane acoustic wave is transmitted into the enclosure. The control systems are designed to reduce the acoustic potential energy inside the enclosure when the incident sound is either harmonic or random. Three control configurations, classified by the type of actuators, are investigated both theoretically and experimentally. They are the use of a structural actuator, the use of an acoustic source, and the simultaneous use of both structural and acoustic actuators. It is shown that the use of both actuators is desirable for the active control of both harmonic and random sound transmission into a coupled structural-acoustic system whose response is governed by plate and cavity controlled modes.