Basic investigation of sound field inside and outside ear canal under ultrasound irradiation

In recent years, high-intensity airborne ultrasonic waves applied technology has been developed actively. Accordingly, there are concerns about the effects of sound wave exposure by high-intensity airborne ultrasonic waves. The sound wave intensity is different near the entrance of the ear canal and near the eardrum, because the wavelength is short in the ultrasonic region. Therefore, it is necessary to know accurately the sound pressure at the eardrum position in considering the effects of sound waves exposure by ultrasonic waves. However, it is difficult to measure sound pressure near the eardrum with a probe microphone because it may damage the ear canal and eardrum. Against this background, we have studied the sound pressure characteristics inside and outside the ear canal when airborne ultrasonic waves are exposed to the mannequin head (KEMAR) with a pseudo-ear canal created to imitate the dimensions of the human ear canal. And, we have attempted to estimate the sound pressure value near the eardrum using the sound pressure in the ear canal. In this report, we verified the sound field inside and outside the ear canal and the sound pressure near the eardrum, when ultrasonic waves (frequency:20 kHz) were irradiated to the mannequin head.