It is well known that the earmold with a vent attenuates low frequency amplification of hearing aid. This low frequency attenuation by vented earmold is utilized for hearing aid in persons with a high frequency hearing loss. We are also beginning to apply this vented earmold to the children with a high frequency hearing loss. According to our experience, the earmold with a 3mm vent in diameter appears to be effective in decreasing the noisy that hearing aid delivered, while speech discrimination score is uneffected.
A mathematical psychophysiological theory is developed for loudness level and loudness as a function of tonal duration. It is based on the psychophysical as well as neurophysiological evidences that the apparent temporal summation of acoustic energy are the results of neural summation at a higher level of the auditory system and of inhibitory interaction and feedback in the peripheral auditory system. The results as follows: 1) Temporal decay of neural activity due to inhibitory feedback can counteract the effect of nonlinearity in the peripheral system to produce psychoacoustic characteristics that act as if it were an acoustic energy integrator. 2) At the same time, inhibitory feedback substantially reduces the effect of temporal summation on loudness. 3) Psychoacoustic characteristics of equal loudness summation as a function of tonal duration parallel these of a linear temporal integrator of acoustic energy can understand that is due to the effect of inhibitory feedback in the peripheral auditory system.
The result of observation of the effect of sound load on extrinsic tinnitus of 1, 354 cases was as follows: 1) The response was higher on the side where sound load was laid than on the other. The subjects were classified into the young group, the middle-age group, and the old group, and the response to sound load seemed to be the highest in the middle-age group. 2) When the subjects were classified into groups according to the causes of tinnitus (such as head trauma, noise trauma, miscellaneous cases), then according to qualities of tinnitus (such as continuous, intermittent, non-tinnitus), it was found that greater differences in response to sound load were significantly observed among the latter groups than among the former. 3) Among the patients in the groups classified according to their qualities of tinnitus, those who showed changes in qualities of their tinnitus were larger in number in younger patients than in older ones, but those who showed a rise or occurrence of tinnitus were larger in number in older patients than in younger ones.
The authors developed a new type of audiometer which automated the pure-tone air-conduction threshold audiometry according to the testing program based on the standard manual audiometric procedure and reported on the outline of the constitution and operation of this equipment. The characteristics of the equipment were as follows: 1) The pure tones of 4 out of 8 frequencies from 125 to 8, 000 Hz could. be voluntarily chosen for automated testing. Programs for subject's instruction and subject's response exercising were stored in this equipment. The exactly same threshold levels were obtained with the devices as those by the conventional manually operated puretone audiometric procedure to minimize the errors during the test. 2) The operating personnal were not required, and the testing time was short. 3) The equipment could be used manually. 4) The intensity levels and messages obtained either manually or automatically were punched on a paper tape which was off-line batch-processed by a data processing center. As a results, we could ascertain the necessity of the masking, errors during the testing, and whether the obtained intensity levels were correct or incorrect.
The author reported a case which showed a deterioration of hearing after wearing a hearing aid. The girl who was 6 years old and had a congenital deafness showing bilateral and symmetrical perceptive hearing loss in moderate degree of horizontal type, wore a hearing aid in her left ear. On 40 days after the initial use of hearing aid, a hearing test disclosed deterioration of the hearing in the aided left ear. The author suspected hearing aid trauma and recommended to remove the aid from the eft ear for time being. But the hearing acuity did not recover to its former level. The aid was changed to the right ear and after 8 months, no threshold shift in the right ear and no recovery in the left were observed. The author pointed out in this case that several conditions, such as, the susceptible age for hearing shift, endogenous deafness, the use of powerful hearing aid, suddenly raising of the amplification, and unsufficient use of ARC-equipment, gave a countenance to the hearing aid trauma.
A 49-year-old man was diagnosed as glomerulonephritis in 1962. The patient underwent haemodialysis 23 times until 1971. On 19 October 1971, the patient came to the Tokyo Metropolitan Okubo Hospital, and on the examination, there was no abnormal findings in the ear drum, x-ray film of the temporal bone, and on the vestibular functional test. Audiogram revealed perceptive deafness, gradual threshold shift in the higher frequency range. On 20 October, 1971 the patient admitted to the hospital for recieving haemodialysis. The patient was discharged from the hospital after 21 times haemodialysis. Thereafter, haemodialysis was carried out 40 times until the death on 19 May, 1972. Before the death, hypertension, increase in serum K-concentration, rapid increase in body weight due to edema, and decrease in body weight due to haemodialysis were noted. Histopathological examination of the temporal bone revealed mild fibrous thickening of the mucous membrane of the tympanic cavity, cord-like fibrous tissue around the round window niche loss of the outer hair cell confined to the basal end of the organ of Corti, and morphologic evidence of hydrops of the cochlear duct resulting in collapse of the organ of Corti. There was no remarkable change in the stria vascularis and spiral ganglion.
Difference limen for the frequencies (DLF) and the formant frequencies (DLFF) were examined in 5 children of normal, hard of hearing and deaf as the test of auditory discriminability. DLF of the normal and the deaf children were 0.6-1.2% and 5.6-11.4% respectively DLFF of the normal and the hard of hearing children 5.5-6.9% and 12.5-27.2% respectively. Vocal pitch matching (VPM) and variability of formant frequencies (VFF) were examined on the same subjects as the tests of motor function. VPM of the normal and the deaf were 1.6-2.2% and 17.8-30.2%, respectively. VFF of the normal, the hard of hearing and the deaf were 5.0-7.6%, 9.9-25.3% and 28.3-46.6% respectively. The results described above showed the almost same values between auditory discriminability and motor normality in speech behavior. From these results, the author hypothized that measurement of the motor variability in speech behavior will be useful in the judgement of grade on the speech disordres, prognosis and training effects.