Multiple-Point Equalization in a Room Using Adaptive Digital Filters

A method is present for designing an equalization filter for a sound-reproduction system by adjusting the filter coefficients to minimize the sum of the squares of the errors between the equalized responses at multiple points in the room and delayed versions of the original electrical signal. Such an equalization filter can give a more uniform frequency response over a greater volume of the enclosure than a filter designed to equalize at one point only. The results of computer simulations are presented for equalization in a 'room' with dimensions and acoustic damping typical of a car interior, using various algorithms to adapt automatically the coefficients of a digital equalization filter.