On the occurrence of noise deafness, the significance of conductive deafness has been discussed from the various angles, and very different opinions have been emphasized respectively by the different authors.
In this observation, 21 workers with unilateral conductive deafness were selected from 419 workers who have been worked in the noisy environment of Japanese National Railways. Among of the selected cases, the clear sign of noise deafness was proved in either or both sides in 16 cases. On these 16 cases, the comparison of the hearing pattern between both side was made in order to evaluate the effect of conductive deafness upon the occurrence of noise deafness.
In most cases, no sign of the noise deafness wasf ound in the side at which the ear has the conductive lesion for a long time of period. From this result, it can be said that the conductive deafness shows the so-called ear-plug effect and might be a defensive factor to the occurrence of noise deafness. However, in a few cases, whose ears have been exposed to an intense noise with severe vibration, the sign of noise deafness was proved also in the side of conductive lesion. This might indicate that the conductive deafness rather accelerates the occurrence of noise deafness under the noisy environment with intensive vibration.
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