Pauli Minnaar

Determination of optimal HRTFs for binaural synthesis

Earlier studies have shown that a carefully selected human substituting an artificial head can minimize the amount of localization errors for a group of people in a listening experiment, thus indicating that a set of head‐related transfer functions (HRTFs) can be found, which to some extent fits a population. This study aims at exploring ways of designing such general sets of HRTFs suitable for larger populations. An effort is put into considering the importance of, e.g., different frequency regions of the transfer functions in order to focus on the most general characteristics and avoid focusing attention on highly individual features. The physical origin of the different parts of the HRTFs will be taken into consideration, and HRTF design methods using parameters derived through signal analysis will be studied.

Inverse filtering of headphones for binaural sound reproduction

Binaural recordings can be made at a blocked ear canal entrance and can be conveniently played back over headphones. The total transmission is then characterized by a transfer function that includes the responses of the headphone and the microphone as well as the transmission between them. The transfer function can be broken up into a minimum phase and an excess phase component, of which the latter can again be broken up into an all‐pass and a linear phase component. In order to make the binaural system acoustically transparent, an equalization filter must be designed as the inverse of the total transfer function. The suitability of various filters for inverting each of the transfer function components is evaluated using data from real ear measurements. The robustness of the equalization is discussed with respect to slight changes in headphone and microphone placement. For the investigation 2892 measurements were made on a range of people wearing various types of headphones and wearing different samples o...