Issues on Dummy-Head HRTFs measurements

The dimensions of a person are small compared to the wavelength at low frequencies. Therefore, at these frequencies HRTFs should decrease asymptotically until they reach 0dB -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.