抄録
Those who work in factories or in high-speed transport facilities are generally exposed to vibration all over the body as well as to noise. On the influence of noise and vibration that the acoustic organs are subject to, a lot of tests on animals have been made, but none on human beings.
Using a new vibration-generator of my own devising, I tried a test on ten healthy young men and women. The conditions under which I tried the test were as follows: the frequency of the vib., 1000 per minute ; the amplitude, 3 mm ; pitching vib. ; the period of the test, 30 minutes at a time. The result of the test has revealed the fact that vibration adds to the power of hearing, white noise (white noise, 100 phon, 30 minutes) considerably attenuates it. But when vibration and noise are given at the same time, it gets still weakened. The hearing loss is striking at and around 4000 cps and C5 dip gets still more deepened than when it is caused by noise alone. The hearing loss in high and lowcompass is not evident.
Next I measured the retraction grade of the eardrum, by means of giving pure tone (1000 cps, 100 phon) to the ear immediately after charging them with vibration. When the vibration was given, the eardrum caved in actively and its angle was great, which, however, were weakened with the charge of noise.
From the above-said results, I have got to the conclusion that the existence of vibration is not harmful to the acoustic organs in itself, but when attended with strong noise, it becomes very harmful.
