The project investigates dynamic issues related to the human perception of virtual auditory environments. Three-dimensional sound is simulated by means of binaural synthesis based on generic head-related transfer functions (HRTFs). The HRTFs are updated as a function of time in order to implement moving sound sources and/or in response to the listener's head movements. Perceptual aspects related to the updating are studied in psychophysical experiments. To this purpose, engineering aspects of the system, corresponding to spatial resolution of the HRTFs, filter-switching techniques and update rate are evaluated and related to their perceptual effect. The results will help at determining the needed accuracy of the engineering aspects, so as to implement a perceptually adequate three-dimensional sound system. Investigations on spatial resolution of HRTFs and filter switching techniques are ongoing and described in separate projects ("Audibility thresholds for HRTF-switching in binaural synthesis" and "Audibility of differences between adjacent HRTFs"). Supported by STVF/FTP.