Perception of a Spectrally Deprived Speech Signal

It was found that, at a test bandwidth range of 50 Hz, 100% speech intelligibility is retained in naive subjects when, on average, 950 Hz is removed from each subsequent 1000-Hz bandwidth. Thus, speech is 95% redundant with respect to the spectral content. The parameters of the comb filter were chosen from measurements of speech intelligibility in experienced subjects, at which no one subject with normal hearing taking part in the experiment for the first time exhibited 100% intelligibility. Two methods of learning to perceive spectrally deprived speech signals are compared: (1) aurally only and (2) with visual enhancement. In the latter case, speech intelligibility is significantly higher. The possibility of using a spectrally deprived speech signal to develop and assess the efficiency of auditory rehabilitation of implanted patients is discussed.