We examined psychophysical tuning curves (PTC) and distortion product otoacoustic emissions (DPOAE) in the normal ears and discussed the relation between these two phenomena. The stimulus levels of f1 and f2 in DPOAEs measurement were set so as to make those geometric means (GM) 1, 2 or 4kHz. The sound pressure level of f2 was less than that of f1 by 10dB and the ratio of f2/f1 was 1.2. Simultaneous PTC was obtained by determing the minimum level of a pure tone masker to mask the probe tone (0.5, 1, 2, 4kHz) 10dB above the threshold. When f1 in DPOAEs was regarded to be equivalent to that of the probe tone in PTC, the frequency at inflection point of PTC where “tip” meets “tail” was coincident to that of DPOAEs at the corresponding frequency. Considering that DPOAEs relate to the active process of the cochlea, the coincidence of DPOAE and PTC is considered to be a phenomenon indicating that both of them closely relate to the frequency selectivity of hearing.
Dominant negative SP in Meniere's disease correlated with the high plasma antidiuretic hormone (p-ADH) level was reported. However, the previous study had a statistical error of type 2 because number of cases were few. In the present study, the number of the cases was increased over twice, and we had nearly the same results as the previous one. The dominant negative SP was not closely linked to p-ADH level that measured within 2 weeks before or after electrocochleography was tested. But, in the patient groups with a persistant high p-ADH level or a history of high level, the SP/AP ratio statistically tended to be higher. The pathogenesis of the dominant negative SP remains unknown. Recently, the dominant negative SP is thought to be resulted from hair cells disfunction and/or increase of potassium ion, because the dominant negative SP does not easily normalize despite of hearing improvement. Our speculation is that an increase of negative SP might reflect the hair cell disorders and/or changes of membranous permealility indused by over-accumulation of endolymph resulting from an elevation of ADH.
The influence of noise induced temporary threshold shift (NITTS) on EOAE was investigated. The high intense sound exposure with 100dB white noise and 90dBnHL 1kHz pure tone comparatively was done. Amplitude of EOAE evoked with 1kHz tone burst was recorded as parameter. There was no significant change on amplitude of the EOAE, including for seconds soon after 100dB white noise exposure. On the other band, after exposure to 90dBnHL 1kHz pure tone, the amplitude reduction of EOAE was recognized among the subjects who had the TTS for a few minutes (so called ordinary TTS). These results suggested that there was a close relation between ordinary TTS and reduction of EOAE amplitude.
32 children (6-15 years old) suspected of functional hearing loss with school screening test were investigated especially by pure tone audiometry. 26 cases out of 32 (81%) performed pure tone audiometry successfully, and their hearing acuity were confirmed as normal. And most of them visited clinic only once or twice. But they required a devised method of the pure tone audiometmy. The other 6 cases out of 32 showed unreliable data, and their hearing acuity was confirmed as normal by another method such as auditory brainstem respons. The first 26 cases and the other 6 cases showed different types on Bekesy audiometry and speech reception threshould test. For children suspected of functional hearing loss, pure tone audiometry should be performed at a first visit.
Otoneurological findings in 2 cases of acute hearing loss due to rubella were reported. A 37-year-old man complained of hearing loss 2 weeks after rubella infection. Audiogram showed 39dB sensorineural deafness 3 days after onset. The diagnosis was confirmed serologically by rising rubella complement fixation reaction antibody titer 16:1 and positive specific IgM. The other patient was a 37-year old man who complained of tinnitus and fullness of ear one week after rubella infection. Audiogram showed 14dB sensorineural deafness 7 days after onset. The rubella haemangglutination antibody titer rose from 8:1 in the first week to 128:1 one week later. The hearing loss of these cases was improved four month after onset. From these findings we concluded that rubella infection played an etiologic role in sudden deafness. Separately from the above 2 cases, we measured the rubella IgM antibody values in the serum of 131 patients with sudden deafness. In all of the cases the IgM value was negative.
Auditory event-related potentials (ERPs) were assessed in 6 normal subjects in awake state when the oddball paradigm were manipulated repeatedly 3 or 4 times to study the reemergence of P300-amplitudes and the characteristics of a single P300 wave form by the adaptive correlation filter. As the results, the grand average of P300 correlation values had a tendency to decrease from the third session but was not stastically significant. In only two subjects, it was significant at the final session. The single P300 wave form which had a rapid descendent slope was asymmetrical. The duration was about 200ms. The averaged peak latency jitters was 22ms, SD, 22.
Some of recent hearing aids are featured with level compression circuits to compensate the recruitment. Gains of such a hearing aid for a specific input level at a frequency should be so determined that the loudness of the input for a impaired subject becomes as much as that for those with normal hearing. Therefore, it is important to estimate loudness functions, which describe loudness growth as a function of input signal level correctly. In this paper, application of the rating scale method for estimating loudness functions is considered. In particular, subdivision (two-step) rating scale method was focused on. First, Japanese adverbs and adjectives to represent rating scales that ranges from the threshold of hearing to UCL were examined. Next, loudness functions were measured with the subdivision rating scale method. The results of the subdivision method were compared with those of the conventional (single-step) method by regarding subjects judgments at the first step of the subdivision method as the result of the single-step method, and showed that the variance of the result of the subdivision method was smaller than that of the single-step method.