Issues on Dummy-Head HRTFs measurements

Head-related transfer functions (HRTFs) contain the transformations that affect the sound in its path to the eardrum of a listener.  As the dimensions of a person are small compared to the wavelength at low frequencies, HRTFs should decrease asymptotically in that range 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.  As a contribution to a current international round robin of HRTFs measurement systems, we have measured HRTFs of the dummy-head Neumann KU-100 for 85 directions in an anechoic chamber. These HRTFs measurements are used in this project as a case study to investigate different issues associated to calibration, DC correction and low-frequency response.  Informal listening tests have been conducted, which suggest that these issues can affect the sound quality.