Acoustic Modeling and Control of Conical Enclosures

Abstract

Acoustic modeling and control of conical enclosures with an actuator boundary condition is presented. Acoustic impedances are coupled with electrical and mechanical actuator dynamics to generate a coupled state-space model of the system. Analysis of the acoustic impedance illustrates that pole-zero cancellation occurs when the length of the conic section becomes large compared to the distance from the apex to the actuator boundary condition. Used as a platform for control design, positive position feedback is applied for acoustic attenuation. The model predicts the first four resonance frequencies to within 1.75 percent of experimentally measured values. Standing waveforms are presented and related to the effects of the actuator boundary condition. A feedback controller is implemented on an experimental testbed with global reductions of 38.4 percent or 4.2 dB observed over a 50-400 Hz frequency range. Experimental results demonstrate that global sound attenuation is possible with a single feedback channel.