Speech perception with steeply sloping hearing loss: effects of frequency transposition

Six adults with a very steeply sloping high-frequency hearing loss listened to monosyllabic words in several conditions. In the first condition, their ability to identify phonemes with a signal-to-noise ratio of 6 dB was measured. Results were similar to those of normally hearing subjects listening to the same material through low-pass filters having comparable cut-off frequencies. In the remaining two conditions, four of the hearing-impaired subjects, and a control group of five normally hearing subjects, listened to speech in quiet with and without frequency transposition. The transposition lowered all speech frequencies by a factor of 0.6. Specific auditory training with transposed speech materials different from the materials used in the tests of speech perception was provided in 10 sessions, each of one hour's duration, which were scheduled at weekly intervals. Despite this training, no significant differences were found between the two conditions in these subjects' recognition of words. It is concluded that such a frequency-transposition scheme, if implemented in a wearable hearing aid, would be unlikely to benefit people with a sloping hearing impairment of this type.