Abstract
Speech perception is known to deteriorate in subjects with sensorineural hearing impairment, due to the increased spectral and temporal masking effects in the peripheral auditory system. As a hearing enhancement technique to deal with this issue, dichotic hearing appears promising. This technique splits speech signals into two complementary parts and presents them dichotically. In the present study, in order to verify the efficacy of this method for dealing with the masking of consonants by the preceding vowels, a listening test was conducted in 27 subjects with mild to moderate high-frequency sensorineural impairment. Forty VCV syllables were divided into two bands taking into account the formant frequency of the preceding vowels. The changes in clarity were analyzed by selecting the dividing frequency and by interchanging the conditions for presenting the high- and low-frequency components. The following results were obtained: 1) irrespective of the dividing frequency, the dichotic listening enhancement effects were observed. However, there were differences in the degree of improvement in the proportion of correct answers among the consonants; 2) intelligibility of the preceding vowels, /u/, /i/ and /e/, improved; 3) the intelligibility could be further improved when a better combination was chosen based on the sum of the hearing acuity for the low-frequency band presenting the low-frequency components and the hearing acuity for the high-frequency band presenting the high-frequency components rather than the sum of the hearing acuity for their complementary bands or vice versa.
