Effects of measured and simulated diffraction from a plate on sound source localization

In daily life, natural or man-made structures influence sound propagation, causing reflections and diffraction with potential effects on auditory spatial perception. While the effect of isolated reflections on binaural localization has been investigated, consequences of edge diffraction on spatial perception have received less attention. Here, effects of edge diffraction on the horizontal localization of a sound source were assessed when a flat square plate occludes the direct sound or produces a reflection in an otherwise anechoic environment. Binaural recordings were obtained with an artificial head for discrete sound source positions along two horizontal trajectories in the vicinity of the plate, including conditions near the incident and reflection shadow boundary. In a listening test, the apparent source position was matched for conditions with and without the plate, resulting in azimuth offsets between the apparent and physical source of up to 12 degrees. The perceived direction of occluded frontal sound sources was laterally shifted to the visible region near the edge of the plate. Geometrical-acoustics-based simulations with different methods to binaurally render diffracted sound paths were technically and perceptually compared to the measurements. The observed localization offset was reproduced with the acoustic simulations when diffraction was rendered considering the individual ear positions.