Study on 3-dimensional spatial hearing and its control for highly advanced acoustic communication

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In this fiscal year, sound reproduction accuracy of the auditory display proposed last fiscal year was analyzed in detail. The results showed that the error level of around-20 dB can be achieved. This was represented in an international conference on acoustics held last October in Kumamoto.The Effective coding methods of Room Transfer Functions (RTFs) and Head-Related Transfer Functions (HRTFs) were also investigated. Common-pole zero modeling of transfer functions proposed by Haneda et al. was applied to the set of RTFs and HRTFs used in our developed model. As a result, it was shown that this method has a potential to code the information involved in these set of transfer functions effectively with less parameters than those modeled by using the conventional FIR filter banks.Since our proposed sound field reproduction system is based on the straightforward modeling of the sound transmission system, this may be redundant when the dynamic change of the system due to the listener's head movement is taken account. Hence the influence of the listener's head movement in directional hearing was focused in our project. The hearing experiment was executed with the real time system changing the transfer functions convolved with the sound source signal according to the relative position of the sound source and the listener's ears due to his/her head movement sensed by a magnetic sensor. The results showed that the listener's head movement is significantly effective and taking into account the dynamic change is important in the highly accurate auditory display.