We performed the band noise masker (BNM) therapy for the suppression of tinnitus. Spontaneous otoacoustic emissions (SOAEs) were measured before and after BNM therapy and the correlation between the efficiency of BNM therapy and changes of SOAEs was analysed. There were no significant correlations between pitch of tinnitus and frequency of SOAEs, and loudness of tinnitus and amplitude of SOAEs. Before and after BNM therapy, the frequency and amplitude of SOAEs did not changed significantly. In conclusion, it was predicted that SOAEs had little relation to tinnitus.
The equivalent dipoles for ABR were estimated using the Dipole Tracing Method (DTM). 10 adult-healthy volunteers were employed for this study. The subject was laying on an EEG chair with closed eyes and presented clicks of 80dBnHL monaurally as the acoustic stimulation with/without masking noise to the contralateral ear. 21ch ABRs were obtained. Then, the grand averaged responses (GAs) among all subjects were calculated. The GAs were divided into the filtering ranges of 20-1500Hz (slow+fast band), 20-300Hz (slow band), and 300-1500Hz (fast band) with the FFT based digital filter. The waves IV, V and VI for these filtering ranges were analyzed using DTM. The dipoles for 20-1500Hz (slow+fast band) and 20-300Hz (slow band) were localized on the mid brain and the thalumus. The estimated dipoles without masking noise in the range of 20-1500Hz were not divided into each wave. Those in the range of 20-300Hz were scattered or located different positions that will be resulted in the effects of both shadow response and binaural interaction.
Twelve cochlear implant patients (34-77 years old) were examined by pure tone audiometer in terms of their abilities of discriminating the loudness, frequencies, and interval time between pulses and identifying the speech sounds of vowels and consonants. The results indicated that speech perception would be affected by the psychoacoustic factors. It was found that their abilities deteriorated in proportion to the length of auditory deprivation, and the patients who had auditory deprivation for more than 30 years showed the lowest discrimination abilities. Therefore, cochlear implant should be recommended soon after the onset of auditory deprivation because of the plasticity of brain functions.
Since April 1977, the Japanese goverment has sponsored the screening tests for the early detection of severe hearing impairment in one and a half-year-old infants as part of the national health program. The authors carried out a pilot study of the screening tests consisting of questionnaires and behavioral observation audiometry (BOA), to detect a moderate or severe hearing impairment in infants born with a high-risk for hearing impairment. After we confirmed the usefulness of our screening tests in the pilot study, we attempted to apply the screening tests for one and a half-year-old infants. The results obtained were as follows: (1) Our screening tests were able to detect hearing impairment over the moderate degree in one and a half-year-old infants with a congenital high-risk for hearing impairment. (2) In the general health examination for the one and a half-year-old infants, BOA should be included to select those who will need further examinations, because only the questionnaires are insufficient to detect hearing impairments. (3) It would be better to use a standardized tone and sound pressure level in BOA.
Incidence of monosyulables was studied in Japanese scenario for teleplays. The incidences of the monosyllables were 19.3% for vowels without consonants, 84.7% for consonants with vowels and 6.0% for /n/ without vowels. Consonants having higher incidences were /t/, /k/, /n/, /s/ and /r/. Discrepancies were evaluated between distributions of the monosyllable incidences in Japanese conversation and those in word lists for speech discrimination tests, such as 57S list, 67S list, 100 monosyllable list and 14VCV list. The discrepancy was smallest in the 57S list. To evaluate the understanding ability of conversation from the results of discrimination tests, the results must be interpreted by taking account of the incidences of the monosyllables, especially in the 100 monosyllable list and the 14VCV list.