THE PERFORMANCE OF ADAPTIVE NOISE CANCELLATION SYSTEMS IN REVERBERANT ROOMS

The performance of adaptive noise cancellation (ANC) systems in a reverberant room is investigated. Room reverberation effects are modeled through the method of images, incorporating both direct signal and reverberation effects into the room impulse response. The performance of ANC for broadband inputs is examined as a function of reverberation time, noise source location, and the geometry of the room and measurement equipment. Expressions are obtained relating the steady-state minimum mean-squared error and excess mean-squared error to the reverberation time and filter parameters. Nonuniform convergence effects are also investigated and bounds on the eigenvalue disparity are obtained for a given configuration. It is shown that the eigenvalue disparity increases as both the filter length and the distance between noise source and reference receiver increase, approaching a limiting value as the distance from source to reference receiver surpasses the acoustic critical distance.