Dereverberation systems design for room acoustics

Abstract

Partial equalization techniques are very interesting because they simultaneously allow reduction of reverberation effect and implementation complexity of FIR inverse filters. In this work, two different techniques for dereverberation systems design based on partial equalization for room acoustics have been proposed. The Homomorphic method is used to design stable minimum-phase inverse filters (equalizers) for non-minimum-phase acoustic impulse responses corresponding to small and large rooms. In the first proposed approach, some of the dominant poles of the inverse filter transfer function are replaced by new ones before carrying out the inverse DFT. Results for an impulse response measured in the car interior show that by using the modified version we can control the sound quality more precisely than when using the standard method. In the second approach, an iterative simple smoothing is applied to the original impulse response of a large room before its inversion. Corresponding time reduced impulse responses are derived which conform to perceptual principles. The smoothed impulse responses are then used to design equalization filters. Simulation results for a reverberant audio-conferencing room have been validated using listening tests on Texas Instruments DSP board.