ADAPTIVE INVERSE FILTERS FOR STEREOPHONIC SOUND REPRODUCTION

This paper describes a general theoretical basis for the design of adaptive digital filters used for the equalization of the response of multichannel sound reproduction systems. The work presented is applied first to the two channel case and then extended to deal with arbitrary numbers of channels. In the work described, the intention is not only to equalize both the response of the loudspeakers and the listening room but also the crosstalk transmission from right loudspeaker to left ear and vice versa. The formulation presented is thus a generalization of the Atal-Schroeder crosstalk canceller. However, the use of a least squares approach to the digital filter design, together with the use of appropriate modeling delays, also potentially enables the effective equalization of nonminimum phase components in the transmission path. A stochastic gradient algorithm is presented which facilitates the adaptation of the digital filters to the optimal solution, thereby providing the possibility of the design of the filters in situ in a given listening space. The work is illustrated using some experimental results for the two-channel case.