Phonemic restoration in hearing impaired elderly people

Abstract

　Phonemic restoration is the ability to hear and understand, with the involvement of the brain, sound information made unintelligible by noise. We made hearing young people, hearing elderly people, and hearing-impaired elderly people listen to short sentences in Japanese (Japanese Hearing in Noise Test, HINT-J) under five different conditions, an original listening condition (listening to a sentence without alternation), a condition where silent intervals were inserted, and three noise insertion conditions where noise was inserted into the silent intervals with signal-to-noise ratios of 0, -5, and -10 dB, and evaluated the effects of age and hearing impairment on phonemic restoration. In the elderly subjects, insertion of silent intervals reduced the percentage of correct answers; this tendency was stronger in the hearing-impaired elderly than in the hearing elderly. A phonemic restoration effect from inserted noise was observed in all subjects, and was greater when the inserted noise was louder. Such phonemic restoration effects exhibited no clear association with the background factors in the hearing-impaired individuals' hearing ability, speech articulation, age, threshold values for hearing aids, or speech articulation during use. However, the findings suggested that the complexity of the hearing impairment factors in elderly subjects may have had an impact on the phonemic restoration.