| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 102 === The purpose of this study is to develop a binaural measurement system to simulate the human hearing characteristics with dual microphones and simplified head model. This work contains two parts, one is about the human hearing sense, the other is identification of sound source position.
For understanding the characteristics of auditory sense and the main response of head related transfer function, a simplified head model with the external ear size based on ITU-T Rec.P.57 were established. Besides, the simplified model with circular tube as ear canal. The acoustic module of LMS Virtual Lab was used to analyze the transfer function of simplified monaural through boundary element method, then figured out the optimized size for ear canal length. The size for head is designed by referring to ITU-T Rec.P.58.
In this research, we designed two head models, the shape for one of them is designed in accordance with the specification; while the other one is a simple oval geometry, that three axes following the guidelines of specification.
Comparing with the frequency response of HMS Ⅲ.L Artificial Head, we found high pressure gain at resonant frequency, which is attributed to canal cavity and material of the head. To improve the defect of high amplitude response, we utilized bandstop filter of NI LabVIEW DSP module to smooth the response of simplified head model.
The psychoacoustic parameters such as loudness and sharpness had been calculated according to Zwicker and Fastl’s method, the calculations are compared with the experimental data of the four directions(θ=0°、90°、180°、270°) from HMS Ⅲ.L Artificial Head, showing the difference of loudness and sharpness between the two measurement system are within 2.58 sone and 0.2 acum respectively.
In addition, the interaural time difference (ITD) can be calculated by dual-delay line algorithm for a low frequency sound, the location in front position of artificial head may be recognized; using this concept, the technology of an identification of sound source position was developed.
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