An auditory screening test was conducted on 274 infants less than 4 months old by means of Infant Audiometer with warble tones of 1kHz and 3kHz (50dB (S. L) at one of Health Centers in Tokyo. An electronic computer (Melcom-70) was used in this investigation. The results were as follows. 1) There was a significant difference in the pattern of hearing responses between 3 months infants and 4 months infants. 2) This auditory screening test was useful for evaluating hearing acuity in infants less than 4 months old as public health service.
The aim of this study is to investigate the relationship between screening level of pure tone audiometry and back-ground-noise level. In the experiment I, the loudness of kack-ground-noise was measured ten quiet rooms in nursery schools and kindergartens selected atrandom in the city of Kanazawa. In the experiment 2, the thresholds (HL; JIS) for 0.25, 0.5, 1, 2, 4, 8kHz pure tones were measured in the presence of the four kinds of loudness levels (40, 45, 50, 55 phon dB (A)) of white noise. The subjects were 48 children aged from three to six (12 children in each age group). The following results were obtained: 1. The loudness levels of back-ground-noise of ten institutions were below 40 phon except intermittent large noise. 2. Asloudness of back-ground-noise was increased, the mean thresholds of each group at each frequencies tended to grow significantly. 3. The mean threshold was mainly increased at 1kHz. 4. The noise level, in which the mean threshold added to three times of SD was within the limits of 20dB (JIS), was below 40 phon in three and four years of the age groups, and below 45 phon in five and six years. 5. From the above-mentioned results and the fact that mild conductive hearing loss was much common in the pre-school children, it was postulated that the screening level of 20dB (JIS) of pure tone audiometry was appropriate.
Vibration mode of the human footplate was studied by means of holographic interferometry. Ten temporal bone specimens were treated as to be observed at the footplate from the inner ear side. The eardrum of each specimen was vibrated with a speaker generated by several test sounds of frequencies within the audible range, and vibration of the footplate was observed and recorded by holographic interferometry. One of the noteworthy findings was that the axis of movement of the footplate seemed to exist at some distance outside of the footplate.
Rowley's syndrome is characterized by 1) lateral cervical fistulae 2) preauricular fistulae and 3) mixed deafness. We found 6 cases of this syndrome in one family consisting of 25 individuals in 4 generations. Audiological evaluations of 5 cases demonstrated that one was completely deaf while the other four had bilateral, asymmetrical, mixed hearing loss. It was thus postulated that the anomaly of ossicles associated with the inner ear disorder were the probable causes of deafness. This syndrome appears to be inherited in autosomal dominant pattern with variable expressivily.
Otolaryngological and audiological examinations were done on the chain saw workers, and eighty seven subjects out of one hundred three workers were studied. No ear infections or hearing loss in past history were detected. The average hearing thresholds for 250, 500, 1, 000, 2, 000, 4, 000, 8, 000Hz in each decade were calculated by using a computer process. There were no remarkable differences of hearing loss in the lower frequencies than 2, 000Hz in each decade, but there were difference more than 20dB in 4, 000 and 8, 000Hz between the second and fifth decades. There were no significant difference according to the years of their experiences. It might be said that the hearing loss of the chain saw workers increased in accordance with the age, and their hearing loss were always worse than that of those working in office, but was better than that of those working in the noisy iron manufacturing industry. A typical pure tone audiogram for the chain saw workers was not a c-5 dip type, but a c-6 injured type. The hearing loss was found in fourteen percents in the second decade, twenty in the third, twenty two in the fourth, and thirty two percents in the fifth.
The changes of Brain Stem Response (BSR) recorded from the vertex of the anesthetized cat were studied after the eighth nerve was sectioned and the cochlear nuclei were destructed. The results and conclusions were as follows: 1. The typical wave form of BSR in cat consisted of the five waves. 2. After the section of the eighth nerve and the destruction of the cochlear nuclei the second to fifth waves were disappeared, but the first wave was not affected. 3. BSR was not recorded after the destruction of the inner ear. 4. The first wave of BSR is considered to be originated at the eighth nerve, and the second wave is supposedly generated at the cochlear nuclei.
To determine the recording site of potentials, marking techniques are very useful. Diffusion, pressure microinjection and iontophoresis can be employed as the means of, injection of dyes. The electrode marking technique with dyes such as Fastgreen FCF, Niagara Sky Blue and Alcian Blue was applied to investigate the intracellular potential of hair cells in the organ of Corti. Alcian Blue was the most suitable dye for marking among them, and the cell identification technique with Alcian Blue was discussed.