Interpolating head related transfer functions in the median plane

This paper describes the interpolation of head related transfer functions (HRTFs) for all direction in the median plane. The interpolation of HRTFs enables us to reduce the number of measurements for new user's HRTFs, and also reduce the data of HRTFs in auditory virtual systems. In this paper, a simple linear interpolation method and the spline interpolation method are evaluated and advantages of both methods clarified. In experiments, the interpolation methods are applied to HRTFs measured using a dummy head. The experimental results show that the two methods are comparable in the best case. The resultant minimum spectral distortion is about 2 dB for both methods. The results clarify that the linear interpolation is effective for a set of elevations selected based on the cross correlation and that the spline interpolation is effective at large and equal intervals. These results indicate that HRTFs in the median plane can be interpolated by the methods.