Head-related transfer function
= Head-related transfer function
{title2=$H(f,\theta,\varphi)$}
A direction-dependent acoustic transfer function from an external source to one ear, including effects of the head, pinna and torso under stated measurement conditions. Individual geometry changes the spectral cues. A pair of such functions predicts binaural signals for a known source; inferring direction from unknown sounds is a harder <inverse problem>.