Effects of thresholding on a small-scale matched filter array

Impulse responses (IRs) from eight microphones were measured in a conference room for evaluation with matched filter array (MFA) processing. Since truncation of the filters can be applied to the MFA with little loss in signal-to-noise ratio (SNR), the effects of diffusion and specular reflections are studied. An amplitude threshold is applied to divide the IR´s into specular reflections and diffusion. The results in terms of SNR and frequency response are shown. Specular reflections are required for MFA processing. For this array, using IR peaks above a 0.15 threshold gives 4.8 dB SNR, a 0.4 dB change, and a 2 dB change in frequency response. Diffusion is removed resulting in fewer stored coefficients, 77 peaks on average rather than all 1600 points