Masking release for speech in listeners with real and simulated hearing impairment

The current study examined the effects of audibility and age on the release of masking for speech in interrupted versus steady-state noise in listeners with real and simulated hearing loss. The absolute thresholds of each of ten hearing-impaired listeners were simulated in normal-hearing listeners through a combination of spectrally shaped masking noise and multiband expansion for the octave bands with center frequencies from 0.25–8 kHz. Each individual hearing loss was simulated in two groups of three normal-hearing listeners (one age-matched group and one non-age-matched group). The speech-to-noise ratio (S/B) for 50%-correct identification of HINT sentences was measured in backgrounds of steady-state noise and temporally modulated (10-Hz square-wave) noise at two overall levels for unprocessed speech and for speech that was amplified with the NAL-PR prescription. Results indicate that the magnitude of the release from masking (the difference in S/B obtained in steady-state versus interrupted noise) observed in individual hearing-impaired listeners was generally well produced in both groups of simulated-loss listeners. Thus, release of masking appears to be determined primarily by audibility regardless of age. Predictions of masking release derived from the Speech Intelligibility Index (SII; ANSI S3.5-1997) will be compared to the observed values. [Work supported by NIH-NIDCD R01 DC00117.]