|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥2,100,000 (Direct Cost : ¥2,100,000)
To determine a reference equivalent threshold sound pressure level for new earphones which are used for audiometer, psycho-acoustical experiments are had to carry out. A purpose of this study is developing a new method to detemine reference equivalent threshold sound pressure level wihtout psycho-acoustical experiments. During the term of this project, we carried out following experiments to clear the effects of noise in an ear caused by the wearing an earphone to the threshold of hearing.
1 Measurements of noise level in an ear canal
The noise levels were measured at the entrance of the ear canal with a small microphone when a subject was wearing an earphone. From this experments, some kinds of noise were observed in subject's ear canal below 100Hz, and it was the level increased when the head-band pressure grew heavier.
2 Measurements of thresholds of hearing varying head-band pressure as a parameter.
Measurements of thresholds of hearing, in which head-band pressure was varied as a parameter, were carried out. From the results, the thresholds were not affected by the variation of head-band pressure.
From the above experiments, it was shown that there was noise in subject's ear canal, and source of the noise does not rlate to head-band pressure. Therefore, we could not resolve what is the factor of depending threshold on earphone type. We should be continue studying to clear the source of noise and how effects the noise to the threshold.