The speech-critical band for vowels in steady and fluctuating backgrounds.
Eric W. Healy, Kimberlee A. Crass, Frédéric Apoux · The Journal of the Acoustical Society of America · 2010
Previous work investigating the frequency resolution employed to process English vowels indicated that the speech-critical band (S-CB) for vowels was greater than the psychophysical critical band. This result suggests that the density of information in the acoustic signal is below the resolving power of the auditory system, and therefore functional resolution is limited by the signal. In the current investigation, the S-CB for vowels was measured in steady and fluctuating backgrounds. Thirty-six normal-hearing listeners heard vowels in /hVd/ context. The stimuli were restricted in overall bandwidth to 1.5 octaves centered at 1500 Hz and presented using vocoder-like processing as 1, 3, 5, 7, 9, or 11 low-noise noise carrier bands. Recognition increased and reached asymptote as the number of constituent bands increased. The carrier bandwidth at performance asymptote was again found to be larger than the psychophysical critical band. Moreover, the resolution of the acoustic signal at performance asymptote was similar across conditions in which the stimuli were presented (i) in quiet, (ii) in steady noise, or (iii) in four-talker babble at various signal-to-noise ratios. These results suggest that the current measure of speech frequency resolution is robust across a number of adverse listening conditions. [Work supported by NIDCD.]