Measurement of acoustic transmission properties of a handset with a piezoelectric vibrator using a head and torso simulator

Abstract

This paper clarifies the difference between the acoustic transmission properties of the pinna simulator and a real pinna by a subjective assessment of the sound produced by vibration of the handset with a piezoelectric vibrator using a head and torso simulator (HATS). Recently, a piezoelectric vibrator that vibrates a pinna to produce and transmit sounds was adopted as a receiver on cell-phones and smartphones to improve perceived sound quality in noisy environments. The HATS, used for handset testing in accordance with ITU-T recommendations, has a silicone-rubber pinna simulator to realistically reproduce natural acoustic properties with its human-like shape and stiffness. However, the handset with the piezoelectric vibrator is beyond the scope and was not tested on the HATS. In this paper, we conducted a subjective assessment test that adjusted the gain of pure tones through the pinna simulator to make them auditorily equal to those through the real pinna. We used the HATS, B&K Type 4128-D. The results showed an effect resembling that of a low-pass filter with an approximate cutoff frequency of 1.5 kHz. This allows an actual sound to be simulated from the sound measured by HATS, using the known difference in frequency response.