Are distance perception and sound externalisation distinct ?

International audienceUsing a binaural room impulse response (BRIR), it is possible to create the feeling of a sound source perceived at a specific point in the space around the listener. Such sounds often also trigger the perception of distance. It is currently not known how much the impression of an externalised sound is related to the perceived distance of the sound source, or how they are distinct from each other. In order to investigate these two percepts, 18 participants listened with headphones to 27 simulated conditions using three different excerpts. During three sessions, participants were asked to judge azimuth, distance, and externalisation. Diotic anechoic stimuli were taken as reference and compared to several sounds obtained after a convolution. For the sounds convolved with a BRIR measured at three different azimuths (0,-30, and 60 degrees) and three distances (0, 3, and 5 meters) in a room, we expect higher externalisation ratings for lateralized sources, while te perception of distance should not change with azimuth. Sounds convolved with BRIRs are also expected to be more externalized compared to sounds convolved with anechoic HRTFs at the same azimuths. To evaluate the possiblity that sounds are more externalized only because they are simulated on the side, broadband ITD & ILD were also applied to the diotic sounds. Furthermore, some BRIR-convolved stimuli were averaged across ears to investigate diotic reverberation. The distance and externalization ratings for all these conditions will be systematically compared and correlated to better understand whether they both correspond to the same percept; while the azimuth ratings will be used as control variables