Higher-Order Directional Audio Coding

The first-order model of directional audio coding (FO-DirAC) estimates a single direction of arrival (DoA) and a global diffuseness estimate that depend on the interactions of all the sound wave contributions arriving in a single observation window. The Higher-Order Directional Audio Coding (HO-DirAC) approach is based on a spherical harmonic (SH) representation of the sound field, equivalent to what is used in non-parametric HOA processing. HOA signals naturally encode the directional properties of the sound field with increased spatial resolution and allow estimation of additional parameters to describe the acoustic scene, compared to a first-order representation. Beamforming in the spherical harmonic domain (SHD) reduces to a simple weight and- sum of the SH signals with the SH coefficients of the beam pattern. The higher-order intensity and diffuseness have the potential to resolve multiple sound events.