Critical bandwidth for phase discrimination in hearing-impaired listeners.
Monaural phase discrimination was evaluated in normal-hearing and hearing-impaired listeners as a function of the frequency separation among components in three-tone complexes. The phases of the center components of 100% sinusoidal amplitude-modulated (SAM) waveforms were shifted by 90 degrees to yield quasi-frequency-modulated (QFM) waveforms that had identical long-term spectra but different envelopes and temporal fine structure. Normal-hearing listeners can distinguish QFM waveforms from SAM waveforms as long as the modulation frequency (frequency separation between components) is less than about 40% of the carrier frequency (center component). Phase discrimination performance (d') was measured as a function of modulation frequency, and critical bandwidths for phase discrimination (CBphs) were specified as the modulation frequency corresponding to a performance index (d') of 1.0. In normal-hearing ears, CBphs increased with stimulus SPL. In hearing-impaired ears, CBphs estimates were equal to or narrower than normal when comparisons were made at the same SPLs; CBphs estimates from hearing-impaired ears were broader (better) than normal only when comparisons were made at equivalent SLs. Differences between CBphs estimates in normal-hearing and hearing-impaired ears are explained by level-dependent auditory filtering and the sensation levels at which comparisons are made, without the necessity to postulate abnormal tuning in hearing-impaired ears.
Nelson
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DA
Department of Otolaryngology, University of Minnesota, Minneapolis 55455, USA.
Schroder
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AC
D000328:Adult; D000368:Aged; D001309:Auditory Threshold; D003051:Cochlea / Q000503:physiopathology; D006309:Hearing; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D011601:Psychophysics