|Budget Amount *help
¥2,900,000 (Direct Cost : ¥2,900,000)
Fiscal Year 1999 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1998 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Fitness with the external auditory canal which influences directly is one of the important factors to select earplugs in a noisy workplace. This research aimed at establishing the attenuation test method for earplugs which is applicable to loud environment like the office next to a factory.
The sound localization(SL) method was developed as a hearing test method adopted as the estimation of the attenuation of earplugs by the real ear, and the investigation was made by comparing with the conventional hearing threshold elevation(HTE) method, adding improvement to the experimental devices made in the last fiscal year. Consequently, in ten subjects' average value, the significant difference was not detected for the measured values between the SL method and the HTE method. However, as for standard deviations, those of the SL method were tend to be larger.
Furthermore, when comparison measurement was carried out in five subjects' real ear in case of a larger background noise level, by SL method, the measured values were stable and independent on the value of a background level, but the attenuation measured in the HTE method decreased in the background level of 75 dBA or more.
Moreover, about the test sound used by the SL method, it was found that a narrow band noise was better to carry out localization of sound, and deviations were smaller compared to a pure tone.