Influence on the localization of virtual sound sources using head-related transfer functions with smoothed phase spectra
Bachelor Thesis of Vollmer, Lukas
Head-related transfer-functions (HRTF) describe the influence of body and head on the sound that arrives at the earcanal. This sound contains directional information, which can be extracted by the human ear. One of these cues is the interaural time difference (ITD) that quantifies the time delay between the arrivals of the sound at the left and right ear, respectively. In the frequency domian, time delays are representet as a linear phase but the phase spectra of HRTFs are only approximatly linear. To linearise a function, smoothing algorithms can be used. In terms of HRTFs, these algorithms were mostly used to smooth the magnitude, while the phase spectrum was maintained. Hence, in this study the influence of smoothed phase spectra on the localisation of virtual sound sources is investigated. Therefore different smoothing algorithms are presented and analysed. Because of the smoothing, errors in the ITD are expected, but the analysis shows that phonetic changes occur before the errors in the ITD become perceptible. Thus, instead of a localisation experiment, a perceptional listening experiment was conducted. The results show that the influence of the smoothing, compared to the objective results, has to be reduced, so that no difference between smoothed and original phase is perceptible.