Optimal on-line modeling of primary and secondary paths in active noise control systems.

Abstract

The modeling error shown by the difference of the characteristics between the secondary paths and its models will cause the improper adaptation of the filtered-x LMS adaptive filters in active noise control systems. It is necessary to use the on-line modeling systems for avoiding such improper adaptation, and several on-line modeling methods have been proposed hitherto. Especially, one of them is very useful because the method can identify the primary and the secondary path characteristics without using any additional signal. This method, however, will not always provide the proper modeling results, and the conditions for optimizing the results have not been discussed yet. This paper investigates the conditions for optimal on-line modeling of the primary and the secondary path characteristics without using any additional signal for identification. Theoretical analysis produces the specific conditions which the noise control adaptive filter should satisfy. Those results of the theoretical consideration are confirmed by the computer simulation in which the impulse responses measured in a vehicle cabin are used.