炭鉱従業員の職業性難聴の研究

第五報騒音環境炭鉱労務者の聴力状態並びに各種調査成績との関係, 全篇の総括

抄録

First the hearing in 280 ears of 140 driving men in noisy environment was examined. And the patency of eustachian tube, the retraction grade of tympanic membrane (Prof. Kawata), the development of middle ear pneumatisation, the tonicity of autonomic nervous system, or the vestibular function was examined in order to classify the noise-susceptibility. Moreover, these results were compared with the hearing acuity. The following data were obtained.
(1) The audiogram of a person whose working years count above five years suddenly shows the pathological hearing type, and the increase in hearing loss is parallel with that in working years, the frequency of deafness becoming high rate.
(2) A-type (34.0%), dip type (22.5%), C-type (22.5%), D-type (13.9%), W-type (2.5%), F-type (1.8%), B-type (1.4%), and E-type (1.4%)(Prorf. Kawata) as their hearing types could be measured.
With increase of working year, the hearing type shifts from C5-dip type to abrupt type, and then from abrupt type to declining type.
(3) It is supposed from above results that the driving men engaged for long year (above ten years) show the peculiar hearing impairment namely the occupational deafness.
(4) In the workers, the hearing impairment with tubal stenosis is more severe than the case with good pertubation. The author could not obtain the exact conclusion on the defference of hearing with or without the retraction of tympanic membrane.
(5) The hearing impairment due to acoustic trauma is more slight in the welldeveloped pneumatisation than in the poor pneumatisation.
The air-cell system of mastoid process probably behaves as a protector of labyrinth to intens and continuous sound.
(6) In the test of autonomic nervous system, S₂-type, especially So-type, has the resistance to acoustic trauma, and on the contrary V-type, especially V₂-, V₃-, or V₄-type, has the ausceptibility which may be labile in autonomic nervous condition.
(7) The deviation in waltzirg test (Frcf. Fukuda) was chstived in 41.2 % of workers, and that increased with the increase of working years or with the pregress of deafness. But there was no case of spontaneous nystagmus. Accordingly it is thought that the driving work gives somewhat influence on the vestibular function of driving men.
(8) Finally the consideration of occupational deafness of coalminers was described with the recent investigation of occupational deafness in this country.