| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
In this project, following results were obtained.
1. In order to investigate the effect of high frequency sound on hearing. 15 medical students of normal hearing were examined for test frequency of 4, 8 and 10kHz. As a results, the expsoure to 6 kHz with 100 dB (SPL) and 8 5Hz with 100 (SPL) Induced significant growth of TTS with test frequency of 8 kHz and 10 kHz, respectively
2. Whether or not the critical band with Temporary Threshold Shift (TTS)is affected by high frequency sound exposure was investigated. The function of the cochea and the 8-th nerve in guinea pigs was estimated by the intensity function and maximum output voltage of cochlear microphonics (CM) and by whole nerve action potential (AP). Our results showed that both the intensity function and the maximum output voltage of CM and AP decreaed. AP obtained at the test frequency higher by half on octave than the center frequency of exposed noise was especially lowered. These results suggest that the critical band with TTS
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of both AP and CM may be effected in exposure to high frequency sound.
3. In this experiment using the AP (Action Potential) and EP (Endocochlear Potential) of guinea pigs, experimental exposures to 4 kHz (100 dB (SPL), 20 hours), 8 kHz (100 dB (SPL), 20 hours) and 10 kHz (90 dB (SPL), 20 hours) were investigated. About 80 male guinea pigs, 6 weeks of age, were used. Experimental conditions were as follows. Exp. 1; control: test frequency 9 kHz and 10 kHz. Exp. 2; 8 kHz, 20 hours: test frequency, 9 kHz and 10 kHz. Exp. 3; control: test frequency, 11 kHz and 13 kHz. Exp. 4; 10 kHz, 20 hours: test frequency, 11 kHz and 13 kHz. In these experiment, intensity function of N_1 potential in AP was measures. The N_1 potential of AP induced by a 10 kHz tone burst was remarkably decreased after 8 kHz of tone exposure. And then, N_1 potential of 13 kHz of test pulse tone was remarkably decreased in 10 kHz tone exposure. The absolute value of the negative potential of EP in Exp. 6 (4 kHz; 100 dB (SPL), 20 hours) especially decreased. Less
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