Investigation of a temporal modulation based method on the intelligibility of speech in speech-spectrum shaped noise

Temporal modulation is frequently considered for improving the intelligibility of noisy speech owing to the importance of the envelope in conveying speech information. In this study, we evaluated the performance of temporal modulation on word scores obtained with speech-in-noise. We firstly divided the noisy speech into 16 contiguous subbands from 200 Hz to 6 kHz with bandwidth approximately 1.5xERB of an auditory filter. The temporal envelope was constructed for each subband from the absolute value. It was then low-pass filtered at 16 Hz and used as the instantaneous gain for the subband's noisy speech. We established a psychophysical test (Modified Rhyme Test) with different speech-in-noise SNR values of 0, −3, −6, and −9 dB. Eleven native speakers (age 29 ± 8) with normal hearing were recruited for the study. The signals were processed by MATLAB and presented over earphones to participants seated in an audiometric room. Comparing the processed and unprocessed noisy speech, the mean differences in word scores for SNRs of 0, −3, −6, and −9 dB were −0.4%, 1.5%, −10.5%, and 1.4%, respectively. Using ANOVA, we concluded that the temporal modulation-based algorithm does not produce a statistically significant improvement in speech intelligibility. [Work supported by NIOSH.]