Effectiveness of Time-expansion of consonants for the benefit of Hearing-impaired listeners

ABSTRACT The current paper investigated the efficacy of consonant duration modification or consonant time- expansion on speech intelligibility for the impaired listeners. This work is an extension of author’s previous papers and projects a comprehensive summary of the same along with the correlation of results with the current work. This paper highlights the importance of the lengthening an important acoustic attribute of clear speech - ‘consonant-Duration’. A case for synthetic clear speech in the context of hearing impairment was argued for speech intelligibility. Consonant recognition in noise free and noisy situations using the non-sense syllable test (NST) was investigated upon (i) Hearing Impaired subjects, and (ii) Normal hearing subjects under simulated hearing impairment. Stops and Fricative consonants of English language with cardinal vowels were processed for time expansion. Non-uniform algorithm for waveform expansion involving selection and expansion of acoustic features was adopted. The Burst Duration, Voice Onset Time, Formant Transition Duration for Stops; and Fricative Noise Duration and Formant Transition Duration for Fricatives, were time-expanded by 50 - 100% of original duration. The speech perception in noise tests were quantified in terms of relative information transmission measures. The results reported that among the various segments selected for modifications, only Burst Duration of Stop-vowels has positive benefit on speech intelligibility improvement for the hearing impaired subject while the rest of them lead to perceptual errors.