Numerical studies of acoustic boundary control for interior sound suppression

Abstract

There are two mainstream methods for the active control of noise in enclosures: active noise cancellation (ANC) and active structural acoustic control (ASAC). ASAC systems are most effective when the primary noise source is the radiation from a vibrating structure, but cannot efficiently control sound from other sources. ANC systems are effective when other noise sources are present, but will sometimes require a much higher dimensionality than ASAC systems to control structural radiation. This paper proposes a practically motivated implementation strategy for ANC actuator placement. Specifically, it proposes to implement an array of acoustic control sources in front of vibrating boundaries to form an acoustic boundary control layer. This provides low-power performance comparable to ASAC systems for controlling sound radiation from the boundary, but also an efficient system for controlling noise from other disturbances. Numerical simulations are presented to demonstrate the ability of the acoustic boundary control to suppress interior noise due to acoustic and structural sources. Because of the expense of implementing large active control systems, there is great interest in developing an actuator grouping strategy to reduce the control system 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 of the control problem is studied.