Evaluating the perceptual quality of speech signals enhanced using the Modified Phase Opponency model

Abstract

Previously, we presented a speech enhancement algorithm based on the auditorily motivated MPO model. It was shown that the MPO‐based speech enhancement scheme is robust to fluctuating noise. Compared to the output of several other speech enhancement techniques, the MPO‐enhanced speech signals exhibit the lowest increase in Itakura‐Saito, log‐area‐ratio, and log‐likelihood‐ratio‐based distortion measures as the SNR reduces. In the present work, the performance of the MPO speech enhancement is compared with that of the other techniques using subjective evaluations. Three normal‐hearing subjects were recruited to perform two‐alternative, forced‐choice preference tasks. Each sentence was presented twice: one of them was enhanced using the MPO scheme and the other was either left unprocessed or enhanced using one of three other speech enhancement techniques. Sentences are 5‐digits long and corrupted by additive subway noise at −5, 0, 5, or 15‐dB SNR. Most of the time, the MPO‐enhanced speech signal was preferred weakly. Moreover, the MPO‐processed clean speech signal was preferred over clean unprocessed speech signal just as many times as the clean unprocessed speech signal was preferred, indicating that the MPO processing does not introduce any perceptual artifacts in clean speech. [Work supported by NSF BCS0236707 DOD H9823005C0425.]