Modeling distance-dependent individual head-related transfer functions in the horizontal plane using frontal projection headphones.

The veracity of virtual audio is degraded by the use of non-individualized head-related transfer functions (HRTFs) due to the introduction of front-back, elevation confusions, and timbral coloration. Hence, an accurate reproduction of spatial sound demands the use of individualized HRTFs. Measuring distance-dependent individualized HRTFs can be extremely tedious, since it requires precise measurements at several distances in the proximal region (<1 m) for each individual. This paper proposes a technique to model distance-dependent individualized HRTFs in the horizontal plane using "frontal projection headphones playback" that does not require individualized measurements. The frontal projection headphones [Sunder, Tan, and Gan (2013). J. Audio Eng. Soc. 61, 989-1000] project the sound directly onto the pinnae from the front, and thus inherently create listener's idiosyncratic pinna cues at the eardrum. Perceptual experiments were conducted to investigate cues (auditory parallax and interaural level differences) that aid distance perception in anechoic conditions. Interaural level differences were identified as the prominent cue for distance perception and a spherical head model was used to model these distance-dependent features. Detailed psychophysical experiments revealed that the modeled distance-dependent individualized HRTFs exhibited localization performance close to the measured distance-dependent individualized HRTFs for all subjects.