Audibility thresholds for HRTF-switching in binaural synthesis

The project is part of a general project that investigates aspects of binaural synthesis related to changes in the sound field that occur as a result of moving sound. In order to synthesize these changes, head-related transfer functions (HRTFs) must be updated as a function of time. In this sense, implications of using direct switching of HRTFs are studied. Due to the discrete nature of the spatial representation available from the HRTFs, the switching operation generates artifacts that can be audible, e.g. clicks, and this may affect the perceived quality of the sound. These artifacts should ideally be below the threshold of human perception, here denoted the minimum audible switch, MAS. This project studies MAS in terms of the temporal and spectral characteristics of the HRTFs separately. Psychophysical experiments were conducted in order to measure audibility thresholds for temporal and spectral switching of HRTFs. These thresholds have been defined as the minimum audible time switch (MATS), and the minimum audible spectral switch (MASS). The more general result is that temporal characteristics require a higher resolution than spectral characteristics. Related projects are "Dynamic issues in binaural technology" and "Audibility of differences between adjacent HRTFs". Supported by STVF/FTP.