Equalization in an acoustic reverberant environment: Robustness results

This paper investigates the robustness of sound equalization using a room response inverse filter with respect to changing or uncertain source or microphone positions. It is shown that due to the variations of the transfer function from point to point in a room, even small changes in the source or microphone position of just a few tenths of the acoustic wavelength can cause large degradations in the equalized room response. The robustness problem is especially acute at high frequencies, which are known to carry some important attributes of the speech signal. The spatial extent of equalization, derived from the statistical-average properties of sound transmission in rooms, is illustrated by computer simulations which corroborate the theoretical results presented in the paper.