Auditory Processing of Vowels by Normal-Hearing and Hearing-Impaired Listeners

Abstract

"Masking" patterns were obtained in normal-hearing and hearing-impaired listeners using the pulsation-threshold procedure. Synthesized vowel maskers /a/ and /ae/ were presented at various sound pressure levels and alternated witha sinusoidal probe of a given frequency at a repetition rate of 4 Hz, T = 250 msec. Simultaneous-masking patterns also were obtained in one normal-hearing listener. The vowel pulsation patterns (VPPs) for the normal-hearing listeners closely resembled the acoustic spectra of the vowel maskers. Neither the pulsation patterns for the hearing-impaired listeners nor the simultaneous-masking patterns for the normal-hearing listener preserved the contour of the vowel spectra. These results are interpreted in terms of suppression effects, which have been observed only with nonsimultaneous-masking paradigms in normal-hearing listeners and have not been observed in listeners with a cochlear hearing loss. The effects of increased masker level were the same for both groups of listeners and are discussed in terms of upward spread of masking and a masking function with a slope less than 1.0.