Examining the influence of controlled HRTF-variation on various distance measures
- Research Area:
Master Thesis of Ermert, Cosima Antonia
Binaural hearing is a complex process that is significantly influenced by physical attributes of the listener. These dependencies on the shape of the torso, head but also the resonance properties of the pinna can be summarized in a digital filter, the so-called Head-Related Transfer Function (HRTF). Such HRTFs are not only used widely in entertainment e.g. for virtual reality, but also in medical applications like hearing aid calibration. However, the fact that HRTFs must be highly individual for a realistic listening experience is a major obstacle to their usage. Especially changes in the dimensions of the head and pinna have a significant impact on the orientation ability of the user. Individualized HRTFs are an alternative to individual filters, which can only be recorded with considerable time and computational effort and using special equipment such as an anechoic chamber. An established procedure for the approximation of such individual transfer functions is the principle component analysis (PCA), a statistical method which is used for reconstructing HRTFs depending on the listener’s anthropometric dimensions. However, those simulated filters differ from the actual ones. So-called distance measures are a tool to compare complex filter structures like HRTFs objectively. In this thesis a better understanding of the behavior of distance measures shall be achieved. Various distance measures are presented and evaluated. Hence, simulated HRTFs are varied in a controlled manner to display the behavior of the different distance measures. These insights are then applied to a HRTF data base to compare individualized and individually recorded HRTFs in a meaningful way. The acoustic properties of children’s head differ significantly from those of adults. Therefore, the different distance measures should also be evaluated with regard to their suitability for children’s HRTFs.