Marc Fagelson
Dept. of Speech Commun., Prog. in Commun. Sci. and Disord., Univ. of Texas---Austin, CMA 2.200, Austin, TX 78712
Linda M. Thibodeau
Univ. of Texas, Austin, TX 78712
The spectral center of gravity refers to a listener's averaging of frequency and intensity components when formant peaks in a speechlike signal are separated by 3.5 Bark units or less. In this paper a total of 18 synthetic vowels whose spectra approximated /ae/ or /(inverted vee)/ were generated digitally; each stimulus contained the first 40 harmonics of a 100-Hz fundamental. Nine spectra contained three formants, while the balance contained only two. Subjects with normal hearing and mild high-frequency hearing loss above 3000 Hz were instructed to identify synthetic vowels as either /ae/ or /(inverted vee)/ as F2 frequency was varied between nine different values in 100-Hz steps for both the two-formant and three-formant stimuli. Probit analysis indicated that the normal-hearing subjects identified stimuli more consistently than the mildly hearing-impaired listeners across F2 frequencies for three-formant than for two-formant spectra. The F2 frequency corresponding to the perceived increase in vowel frontness occurred at a lower frequency for normal-hearing listeners. Auditory filter bandwidth was negatively correlated with the F3-F2 Bark difference. Results suggest that spectral averaging may help listeners disambiguate confusing speech signals.