Deep band modulation, frequency discrimination, temporal resolution and audibility effects: phrase perception with and without hearing impairment among older adults

Abstract

Objective The temporal envelope enhancement using deep band modulation (DBM) exaggerates the temporal peaks and valleys in the speech signal, thereby reducing the difficulty in the perception of speech in noise. Method Ten participants in each group of older adults with and without hearing loss in 65 to 83 years were recruited. A repeated measures research design was utilised to investigate phrase perception in unprocessed and deep band modulated phrases at different signal-to-noise (SNR) ratios (−4, 0, and +4). Temporal processing, spectral discrimination and speech intelligibility index were assessed. Results Regardless of the group, the phrase perception in the deep band modulated condition was significantly better than the unprocessed condition at each SNR. A significantly strong negative correlation was observed between: Gap detection threshold (GDT) and phrase perception scores in unprocessed condition at −4 dB SNR in each group; frequency difference limen in each condition and DBM phrase perception at −4 dB SNR in the older adult group with hearing impaired (OAG-HI) group. Furthermore, audibility reflected in the speech intelligibility index (SII) did not influence phrase recognition irrespective of condition, SNRs and group. Conclusion Increased modulation depth enables the participants to use the available temporal envelope, especially at the portion of the phrase where noise is less energetically masked.