Evaluation and Prediction of Perceived Naturalness for Source Directivity With a Visible Virtual Source

In extended reality, dynamic rendering updates the auralization as changes occur in the scene. Directivity is a characteristic that may require dynamic rendering for moving sound sources. This study investigates how the reverberant component of a directional virtual loudspeaker, used as a controlled proxy for a human talker, is perceived as it rotates and whether its directivity contributes to the perceived naturalness of the scene’s acoustics. An experiment was conducted in a virtual environment in which recorded speech and vocal sounds were reproduced through a rotating virtual loudspeaker that was visually overlaid with a human avatar. Four directivity implementations were evaluated: (1) fully measured directivity, (2) direct-sound directivity only, (3) static reproduction without orientation-dependent directivity, and (4) an incongruent inverted-reverberation condition. Participants rated the perceived naturalness of each scene on a seven-point scale. Results indicated that the most physically realistic rendering was perceived as most natural, while partial or incorrect directivity implementations reduced realism. Analysis of the associated acoustic parameters showed that deviations in interaural level difference and direct-to-reverberant ratio were systematically related to changes in perceived naturalness.