Non-monotonic binaural cues: Recent insights from the “Acoustical Bright Spot”

Horizontal-plane sound localization relies on binaural cues, or interaural time and level differences (ITDs and ILDs), created by acoustic interactions with the head. ILDs are known to be non-monotonic functions of azimuth from diffraction of sound around the head (the “Acoustical Bright Spot”), resulting in the predictable mis-localization of tones in the free field by acoustic-hearing listeners [Macaulay et al., J. Acoust. Soc. Am. 127, 1440–1449 (2010)]. This talk reviews Fresnel diffraction and the Acoustical Bright Spot described by Hartmann and colleagues, and summarizes recent findings and experiments inspired by their work. Recent measurements and modeling studies revealed these non-monotonicities are not limited to just ILDs and have complex interactions with properties of hearing devices such as microphone placement and directionality.