Development of the ear insertion-type noise dosimeter with hearing protection

This study developed the ear insertion-type noise dosimeter with an earpiece. This dosimeter is composed of features two microphones, one located at the ear canal entrance, and the other positioned inside the ear canal. The dosimeter calculates LAeq and LApeak at one-second intervals. The device logs data from both the inside and outside microphones for up to 8 hours, and the recorded data can be conveniently accessed and displayed on a smartphone. The difference between the inside LAeq and the outside LAeq indicates the exposed level attenuated by the earpiece. The ear insertion-type noise dosimeter was evaluated in a free field by using an acoustic measurement manikin (KEMAR; GRAS Inc, Denmark). Results obtained in this study showed that the differences between the LAeq in the free field and that at the entrance of the ear canal were found to be slightly amplified by the pinna effect. Also, the LAeqs measured at the microphone that positioned inside the ear canal was consistently 3.2 dB lower on average than that recorded by KEMAR's microphone. These findings suggest that the LAeq on the eardrum can be estimated by using the LAeq measured by the inside microphone. Additionally, the sound attenuation value can be calculated by comparing the values obtained from the outside microphones with those from the inside microphones.