NUMERICAL-STUDIES OF ACOUSTIC BOUNDARY CONTROL FOR INTERIOR SOUND SUPPRESSION

There are two mainstream methods for the active control of noise in en closures: active noise cancellation (ANC) and active structural acoust ic control (ASAC). ASAC systems are most effective when the primary no ise source is the radiation from a vibrating structure, but cannot eff iciently control sound from other sources. ANC systems are effective w hen other noise sources are present, but will sometimes require a much higher dimensionality than ASAC systems to control structural radiati on. This paper proposes a practically motivated implementation strateg y for ANC actuator placement. Specifically, it proposes to implement a n array of acoustic control sources in front of vibrating boundaries t o form an acoustic boundary control layer. This provides low-power per formance comparable to ASAC systems for controlling sound radiation fr om the boundary, but also an efficient system for controlling noise fr om other disturbances. Numerical simulations are presented to demonstr ate the ability of the acoustic boundary control to suppress interior noise due to acoustic and structural sources. Because of the expense o f implementing large active control systems, there is great interest i n developing an actuator grouping strategy to reduce the control syste m dimensionality. A preliminary feasibility study, to establish under which conditions actuator grouping may be successful, is presented. A strategy in which actuators are grouped through an off-line analysis o f the control problem is studied. (C) 1998 Acoustical Society of Ameri ca. [S0001-4966(98)00809-1].