Influence of Filter Characteristics on the Bias of Reverberation Time Estimation
Keywords:
reverberation time estimation, bias analysis, room impulse response, amplitude-frequency response, filter bandwidthAbstract
Bandpass filters with a rectangular amplitude-frequency response (AFR) are relatively easy to implement in the frequency domain by zeroing out spectral components outside the desired passband. An advantage of this approach is the ease of constructing high-order non-recursive filters with a linear phase response. However, as demonstrated in this paper, this benefit comes at the cost of significant bias in reverberation time (RT) estimates, particularly in cases of narrow bandwidth and short reverberation time. It can be assumed that this drawback may be largely eliminated by using filters with a non-rectangular AFR, which is simple to implement in practice. However, the validity of this assumption remained untested until recently. In this paper, the influence of the filter’s AFR shape and bandwidth on the bias in RT estimation is analyzed. It is shown that the bias of RT estimates based on T20 and T30 ranges from 60% to 100% when one-third-octave filters with a rectangular AFR are used in the frequency range of 25–200 Hz. When a Tukey window is used as the filter AFR, the bias can be reduced to 4%. Similar results were obtained for Early Decay Time and T10 estimates of RT.
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