HRTF
Definition
Head-Related Transfer Function — the mathematical description of how sound is filtered by the shape of a listener’s head, ears (pinnae), and torso before reaching the eardrums. HRTFs are the foundation of binaural rendering, enabling headphone playback to simulate sounds coming from specific positions in three-dimensional space.
Context
In Dolby Atmos workflows, HRTF profiles determine how convincing the binaural headphone render sounds. Generic HRTFs work for most listeners but can produce inaccurate localization — particularly for height perception. Dolby has developed a personalized HRTF beta program, and Apple uses ear scanning (via iPhone) to customize Spatial Audio processing for individual listeners. The Neumann KU 100 binaural head physically models a generic HRTF with its head shape, while the 3Dio binaural microphone uses ear-shaped baffles without a full head model. DIY binaural setups (foam mannequin heads with small-diaphragm mics) perform more like a baffle than a true HRTF but still produce a binaural effect.