Assessing Diffraction Perception Under Reverberant Conditions in Virtual Reality

When a sound source is occluded, diffraction replaces direct sound as the first wavefront arrival and can influence important aspects of perception such as localisation. Few experiments have investigated how diffraction modelling influences the perceived plausibility of an acoustic simulation. In this paper, an experiment was run to investigate the plausibility of an acoustic simulation with and without diffraction in an L-shaped room in VR. The rendering was carried out using a real-time 6DOF geometrical acoustics and feedback-delay-network hybrid model, and diffraction was modelled using the physically accurate Biot-Tolstoy-Medwin model. The results show that diffraction increases the perceived plausibility of the acoustic simulation. In addition, the study compared diffraction of the direct sound alone and diffraction of both direct and reflected sound. A significant increase in plausibility was found by the addition of diffracted reflection paths, but only in the so-called shadow zone.