The effect of temporal envelope changes on recognition of normal rate and time-compressed speech by young-old and old-old hearing-impaired listeners.

摘要

When understanding speech in complex listening situations, older adults with hearing loss face the double challenge of cochlear hearing loss and additional deficits of the aging auditory system. Wide-dynamic-range compression (WDRC) is used in hearing aids as remediation for the loss of audibility associated with hearing loss. WDRC processing has the additional effect of altering the acoustics of the speech signal, particularly the temporal envelope. Older listeners are negatively affected by other types of temporal distortions, but this has not been found for the distortion of WDRC processing. The purpose of this research was to determine how older adult listeners compensate for the temporal envelope changes of WDRC. To answer this question, a two-part approach was used, first incorporating acoustic measures and second isolating the compensatory mechanisms the older listener may be using.; Two groups of adults with mild to moderate hearing loss were tested: young-old (62--74 yrs, n = 11) and old-old (75--88 yrs, n = 14). The groups did not differ on hearing loss, cognition, working memory, or health. Participants listened to low-predictability sentences compressed in quiet at each of four selected compression settings that covered a wide range of acoustic effects, quantified by the Envelope Difference Index (EDI). The sentences were presented at three rates: normal rate, 50% time-compressed, and time-restored.; There was no age difference, nor any interactions between age and listening condition. There was a significant interaction between speech rate and EDI value. As the EDI value increased, representing higher amounts of distortion, speech recognition was significantly reduced for the third and fourth EDI values relative to the first EDI value. At the fourth EDI value, this reduction was greater for the time-compressed than normal-rate condition.; It can be concluded that temporal envelope changes are detrimental to recognition of low-context speech for older listeners, once a certain threshold of distortion has been reached. The effect is not age-related within the age range tested here. The results of the time-restored condition suggested that listeners were using acoustic redundancy to compensate for the negative effects of WDRC distortion in the normal rate condition.