Torso and pinna echoes encode sound source direction cues

Evidence

A revealing study of the autocorrelation impulse response was undertaken University of Maryland and the Indian Institute of Technology; one of their results is shown in figure 21.5. The left panel shows an arriving pulse and fast echoes caused by diffraction off structures of the pinna in well under a millisecond, followed later by torso and knee reflections. This is the head-related impulse response, or HRIR, shown as a function of the angle of approach of the sound. On the right, the Fourier analysis of the HRIR autocorrelation shows the notches (antiresonances) and resonances between, also as a function of angle of approach. It is clear there is plenty of data to help us localize sound. — Eric J. Heller, Why You Hear What You Hear- An…, 1938

Categorization

• DEFINE: Defines head-related impulse response (HRIR) and shows how early echoes from pinna, torso, and knees provide directional information.
• SHARE: A good specific detail for someone working on spatial audio or HRTF processing.