The ATK provides two toolsets: FOA (first-order, 4-channel) and HOA (higher-order, (n+1)² channels)

The ATK ships two distinct toolsets. The First-Order Ambisonic (FOA) toolset uses the classic Furse-Malham WXYZ convention, supports matrix and convolution-kernel processing, and is a 4-channel format. The Higher-Order Ambisonic (HOA) toolset represents soundfields at arbitrary precision using more spherical harmonic components: order n produces (n+1)² channels (1st=4, 2nd=9, 3rd=16). HOA uses the ACN ordering and N3D normalization conventions rather than WXYZ/MaxN. In practice, the toolsets are structurally parallel — encoder, transformer, decoder classes exist in both — but have different class names (Foa* vs Hoa*) and incompatible formats that require explicit transcoding to mix. Higher order improves spatial resolution but increases channel count and CPU cost; 3rd order is common, 5th is the practical maximum.

Examples

FOA: FoaEncoderMatrix, FoaRotate, FoaDecoderMatrix — 4 channels throughout. HOA 3rd order: HoaMatrixEncoder.newDirection, HoaRTT, HoaMatrixDecoder.newDirections — 16 channels throughout.

Assessment

State the channel count for 1st, 2nd, and 3rd order HOA signals. Then explain what you must do to use a binaural FOA decoder on a 3rd-order HOA signal.