Subband Optimization and Filtering Technique for Practical Personal Audio Systems

The implementation of personal audio systems in enclosed spaces, such as a car cabin, suffers from severe echoes from surrounding boundaries. In order to focus sound energy on a single seat position, echoes should be controlled by long multichannel filters with up to a few thousand taps for each channel, which leads to increased memory size and computational complexity. In an attempt to design a practical personal audio system, a subband based optimization and filtering technique are proposed. The design of optimal filters for downsampled low frequency responses enables finer control of low frequency echoes without significantly increasing the number of filter taps, while the broadband response of high frequency components can be controlled with a fewer number of filter taps. Experiments conducted in a real car cabin demonstrate that more than 20 dB SPL difference can be achieved across different seat positions with only half the number of filter taps.