Level discrimination of stop-consonant noise bursts by normal-hearing and hearing-impaired listeners.

Abstract

Level discrimination for the consonant noise bursts of the word ‘‘pack’’ was measured in normal-hearing and hearing-impaired listeners. The utterance, produced by a female talker, was digitized at 20 kHz, edited and output via a D/A converter. Using a constant-stimuli 2IFC procedure, listeners had to discriminate level increments ranging from 0.5–7.0 dB in noise bursts either ‘‘in isolation’’ (i.e., excerpted from the word) or in word context. The sensorineural impaired ears had fairly uniform losses ranging from 30–70 dB. In all conditions, burst presentation level was 59–60 dB SPL for normal ears, and 25–30 dB above the PTA for impaired ears (i.e., most of the burst’s spectra were clearly above the audibility thresholds). Discrimination thresholds [P(c)=75] were interpolated from probits fitted to nine-point psychometric functions. In normal ears, thresholds were 1.5–2.0 dB for both the /p/ and /k/ bursts presented ‘‘in isolation.’’ Thresholds ‘‘in context’’ were ∼2.5 dB for /k/ and 3.0–4.0 dB for /p/. Some impaired ears showed discrimination thresholds similar to those of normal ears. [Work supported by OCAST Grant No. HSO-005 and Presbyterian Health Foundation.]