The Head Shadow Phenomenon Affected by Sound Source: <i>In Vitro</i> Measurement

Abstract

This study focuses on establishing an in-vitro sound filed measurement system in order to investigate the effect of sound source angle and frequency on the head shadow effect (HSE). The study used sound stimuli at frequencies of 125 Hz, 250 Hz, 500 Hz, 750 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz, 6 kHz, 7 kHz, 8 kHz, and with sound source positioning at angles of 0, 30, 45, 60 and 90 degrees. It evaluated the effect these frequencies and positioning combinations had on the HSE. When the sound source was positioned at 90 degrees to the ear, this study found that the HSE not only existed at the frequencies of 4 kHz to 6 kHz, but also the HSE could be happened at 3 kHz, 7 kHz and 8 kHz. In addition, a significant influence on HSE was also demonstrated when the sound stimulus was positioned at 45 degrees to the ear, with a frequency range between 3 kHz~8 kHz. As well as considering head and ear anatomy and the head shadow effect when selecting and fitting hearing aids, it is also necessary to consider adjustment to account for angular sound sources at different sound frequencies.