Numerical Evaluation of the Performance of Active Noise Control Systems

Most of the approaches to the prediction of the effectiveness of active noise control systems are analytical in nature. Analytical approaches are limited to active noise control systems where a solution to the governing acoustic wave equation is available. The objective of the investigation presented in this paper was to develop a generalized numerical technique for evaluating the optimal performance of active noise controllers. The numerical technique used as the basis of the numerical analysis is the indirect boundary element method (IBEM). Boundary element methods have been shown to be straightforward and accurate numerical methods for the prediction of the acoustic response of a system. The IBEM numerical procedures are used here to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the noise source strengths or the enclosure boundary description may not be known. Detectors are introduced into the system to deduce the unknown noise source strengths. The performance prediction for a single input, single output system is presented. Analysis of the stability and observability of the active noise control system employing detectors is also presented.