Issues on Dummy-Head HRTFs Measurements
The dimensions of a person are small compared to the wavelength at low frequencies. Therefore, at these frequencies head-related transfer functions (HRTFs) should decrease asymptotically until they reach 0 dB -i.e. unity gain- at DC. This is not the case in measured HRTFs: the limitations of the equipment used result in a wrong -and random- value at DC and the effect can be seen well within the audio frequencies. We have measured HRTFs on a commercially available dummy-head Neumann KU 100 and analyzed issues associated to calibration, DC correction and low frequency response. Informal listening tests suggest that the ripples seen in HRTFs with a wrong DC value affect the sound quality in binaural synthesis.
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