(1) There were hearing-impaired children in whom their hearing aids did not well adjusted, and they felt annoying by loud sounds and took off their hearing aids frequently. In most of them, the hearing aids were equipped with the highpowered peak-type earphones, and the replacement of them with the low-powered wide-type earphones could help them to use their aids more frequently and effectively than before. (2) On the other hand, for the children who had severe loss of hearing in high frequency range, the low-powered earphones were not suitable because their power limitation. They should be fitted with the medium-powered semiwide-type (socalled S-type or N-type), and their word intelligibility scores could be improved to the higher values. (3) Children with severe loss of hearing were fitted with the peak-type earphones because of their high power output, but some children might be annoyed with “hawling” due to their peak characteristics. For these children, the medium-powered wide-type earphones will be suitable, and the children could raise the volume-setting without feedback, resulting in effective use of hearing.
AP and SP responses were investigated by the single electrode technique. The recording sites were the round window, mid-portion of the bony wall of cochlea, the apical portion of the cochlea and bony wall of the hypotympanum. One cycle of sound stimuli at 8kHz, 4kHz, 1kHz and 0.5kHz was used and the sounds were given from 50cm lateral to the tested ear. The tone bursts with duration of 30msec were used as measurement of SP. The results obtained were as follows: The highest value of AP out-put potential was obtained by the round window recording. The highest value of AP out-put potential was obtained by the stimulation of one cycle of 4kHz and 8kHz. The positive SP as seen in the round window recording changed to a decreased positive SP or negative SP at the recording sites except the round window. The SP induced by a tone burst from the round window showed the positive SP at high frequency and the negative SP at low frequency. These results will contribute to the research on the single electrode recording of AP and SP responses in these animals.
Treatment of inner ear deafness is still very difficult even today except in certain cases. As mentioned above, the reason is that original sensory cells which cannot be regenerated lose their responsiveness for good to the sound of the comparable cycle once they have been degenerated and lost. It will be, therefore, the most important the cause quickly if it is ever known or to prevent the cause from getting worse. If one has been affected by deafness unfortunately, whether the cause is known or not, it may be reversible in some cases but grow worse in others, depending on the site and degree of the damage. At any rate, it is necessary to diagnose or apprehend them properly for prevention and treatment of hearing impairment. Discussion is made under general on the ultrastructure of the normal cochlea observed with the scanning and transmission electron microscopy as well as on pathological conditions of the cochlea induced by various causes.