Adaptive Resonant Mode Acoustic Controller

Abstract

Helmhotz resonators are popular devices used for passive noise control. These apparatus can be designed to produce a maximum reduction over a narrow frequency range. The frequency of the resonator is dependent upon its volume and shape. Schemes have been proposed to adapt Helmholtz resonators, through changing physical parameters, such as volume and neck area. A recent study by Bisnette and Vipperman (2004) has modeled the passive Helmholtz resonators and realized them electronically in a process that is similar to positive position feedback control in structures. One key difference is the need for phase compensation of the speaker dynamics, which is accomplished with an all-pass filter. Recent extensions to this control method have examined the advantages of using band-pass versus the low-pass resonant filters as well as higher-order Butterworth bandpass filters. Bandpass filters are found to simplify the multi-modal design process by reducing interaction of adjacent modes. Additional refinements include the adaptation of system parameters. By adapting controller gain, damping and control frequency are examined and optimized. Adaptation of system parameters is greatly facilitated through the electronic realization.