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.