Frequency and amplitude estimation of the first peak of head-related transfer functions from individual pinna anthropometry

The first (lowest) peak of head-related transfer functions (HRTFs) is known to be a concha depth resonance and a spectral cue in human sound localization. However, there is still no established model to estimate its center-frequency F1 and amplitude A1 from pinna anthropometry. Here, with geometries of 38 pinnae measured and their median-plane HRTFs calculated by numerical simulation, linear regression models were evaluated in estimating F1 and A1 from 25 concha depth and aperture measurements. F1 was best estimated (correlation coefficient r = 0.84, mean absolute error MAE = 118 Hz) by lateral distances from the base of the posterior cavum concha to the outer surface of the antitragus and antihelix (longest measures of concha depth). A1 was best estimated (r = 0.83, MAE = 0.84 dB) by the lateral distance from the ear-canal entrance to the side of the cheek near the anterior notch (shortest measure of concha depth) and by the equivalent diameter of the concha aperture. These results suggest that the first resonance's quarter-wavelength corresponds to the longest lateral extent of the concha and that its energy lost to the surrounding air depends on the concha aperture and the cavum concha's shortest lateral depth.