Modifying the reverberations rendered from original impulse-response records is an essential three-dimensional audio technology. A nonparametric method is proposed for modifying the reverberation time, maintaining the frequency response trend (frequency locations of the spectral peeks and troughs) so that entire tonal characteristics might be preserved. The method can be interpreted to move the poles and zeros of the transfer function close to (for making reverberations longer) or far from (for shorter reverberations) the unit circle in the z plane. Exponential time windowing moves the minimum-phase zeros along the radial direction, while the pole and zero symmetrical locations of the all-pass part can be controlled after causal and noncausal cepstral decomposition. The locations of the all-pass poles can be moved by exponential windowing the time response reconstructed from the causal cepstrum component. The causal cepstrum obtained again after moving the all-pass pole locations is utilized in creating the noncausal part of the modified all-pass phase cepstrum. Rendering of the reverberation effects on the frequency response in which the frequency response trend is confirmed. Examples of frequency-dependent reverberation control applications are also given.
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