THE EFFECTS OF HEARING-LOSS AND NOISE MASKING ON THE MASKING RELEASE FOR SPEECH IN TEMPORALLY COMPLEX BACKGROUNDS

Speech recognition was measured in three groups of listeners: those wi th sensorineural hearing loss of (presumably) cochlear origin (HL), th ose with normal hearing (NH), and those with normal hearing who listen ed in the presence of a spectrally shaped noise that elevated their pu re-tone thresholds to match those of individual listeners in the HL gr oup (NM). Performance was measured in four backgrounds that differed o nly in their temporal envelope: steady-state (SS) speech-shaped noise, speech-shaped noise modulated by the envelope of multi-talker babble (MT), speech-shaped noise modulated by the envelope of single-talker s peech (ST), and speech-shaped noise modulated by a 10-Hz square wave ( SQ). Threshold signal-to-noise ratios (SNRs) were typically best in th e ST and especially the SQ conditions, indicating a masking release in those modulated backgrounds. SNRs in the SS and MT conditions were es sentially identical to one another. The masking release was largest in the listeners in the NH group, and it tended to decrease as hearing l oss increased. In 5 of the 11 listeners in the HL group, the masking r elease was nearly identical to that obtained in the NM group matched t o those listeners; in the other 6 listeners, the release was smaller t han that in the NM group. The reduced masking release was simulated be st in those HL listeners for whom the masking release was relatively l arge. These results suggest that reduced masking release for speech in listeners with sensorineural hearing loss can only sometimes be accou nted for entirely by reduced audibility.