ATK Glossary | SuperCollider 3.13.0 Help

A-format: Component or signal set in the angular domain, evenly distributed across the surface of the sphere in a spherical design. Within the context of the Ambisonic Toolkit, any required equalisation or radial filtering is expected to have been applied. In other words, the Ambisonic Toolkit views A-format as a uniform spherical decomposition of the soundfield.
AL degree (ℓ): Associated Legendre degree. A complete coefficient set of a given Ambisonic order n includes AL degrees ℓ <= n. See Associated Legendre polynomials
AL index (m): Associated Legendre index. (Confusingly, also known as Associated Legendre order.) In conjunction with Associated Legendre degrees references individual spherical harmonic components, in the form (ℓ, m). Associated Legendre indices range |m| <= ℓ for a complete coefficient set of a given degrees. See Associated Legendre polynomials
acoustic admittance: Vector quantity, reciprocal of acoustic impedance, which may be regarded as a normalised form of sound intensity. See Acoustic impedance.
acoustic wavenumber: Spatial frequency of a sound wave, measured in radians per meter.
active: Describes the real, in phase, part of a complex soundfield. See also reactive.
Ambisonic equivalent panning (AEP): Complete the Ambisonic panning law by combining Ambisonic encoding and decoding into a single operation.
Ambisonic order: Specifies the maximum AL degree, ℓ, of a given signal set.
angular domain: Information represented in terms of angular basis functions.
Associated Legendre functions (AL): The well-behaved solutions of the general Legendre equation, which play an important role in the definition of spherical harmonics. See Associated Legendre polynomials
B-format: Component or signal set in the spherical domain. In classic first order Ambisonics, aka Gerzonic, B-format indicates a signal encoded where Ambisonic order n = 1, and components are ordered and normalised by the (now named) Furse-Malham and MaxN conventions. B-format is often used to indicate any Ambisonic signal set, without regard to Ambisonic order, component ordering or normalisation.
basic: Ambisonic Toolkit soundfield designation. A signal, transform or coefficient set with all real modal components.
basic wave: Ambisonic Toolkit soundfield designation. A travelling wave encoded with all real modal components. I.e., a travelling wave encoded at the reference radius.
basis function: An element of a particular basis for a function space. See Basis function.
beam: Window in the spatial domain.
component normalisation: Spherical harmonic coefficient normalisation convention. E.g., maxN, N3D, SN3D. See normalisation.
component ordering: Sorting or ordering convention applied to arrange spherical harmonic encoding coefficients and resulting signal sets. E.g., Furse-Malham (FuMa), Ambisonic Channel Number (ACN), Single Index Designation (SID). See ordering.
decode: Transform a spherical domain signal to the angular domain. Decoding is the end of the Ambisonic panning law.
decoding radius: The radius at which a given signal set is decoded to the angular domain. If no radial filter is applied, the decoding is described as basic, and as a result is decoded at the reference radius.
diffuse field: Complex isotropic soundfield.
dimensions: Two dimensional (2D), pantophonic, or three dimensional (3D), periphonic.
NOTE: The Ambisonic Toolkit does not offer mixed order encoding or decoding.
effective radius: Radius of the volume (or area) of exact soundfield reconstruction.
encode: Transform a signal set into the spherical domain. Encoding is the beginning of the Ambisonic panning law.
encoding radius: The radius at which a given signal set is encoded into the spherical domain. If no radial filter is applied, the encoding is described as basic, and as a result is encoded at the reference radius.
energy localisation vector (rE): Vector quantity offering an estimate of the perceived localisation of a phantom source in terms of energy, expected to predict imaging between 500 and 5000 Hz.
far-field: Characterized by a minimally reactive travelling wave. I.e., a wave with minimal quadrature components. A planewave is in the far-field. See also near-field.
First Order Ambisonics (FOA): Ambisonics employing components up to AL degrees ℓ <= 1.
focused source: Phantom image appearing within the radius of the reproducing loudspeaker array.
format: Ambisonic Toolkit designation indicating Ambisonic component ordering and component normalisation. E.g., ACN-N3D.
Gerzon energy vector: See energy localisation vector.
Higher Order Ambisonics (HOA): Ambisonics employing components up to AL degrees ℓ <= Ambisonic order n.
holographic: Capable of capturing, reproducing or otherwise synthesizing the complex features of a soundfield, including the sound pressure field, particle velocity field, and sound intensity field.
holophonic: See holographic.
image: Synthesize, modify or otherwise control the phantom images generated by a panning law.
isotropic: Uniform in all directions.
kind: Ambisonic Toolkit operation ID, e.g., \quad.
look direction: The perceived localisation direction a listener would identify as a source origin.
Makita localisation vector: See velocity localisation vector.
near-field: Characterized by a highly reactive travelling wave, where active and reactive intensity vectors are aligned. A spherical wave is in the near-field. See also far-field.
near-field compensated (NFC): In classic Gerzonic first order Ambisonics, near-field compensation describes the near-field control applied to accommodate for decoding loudspeakers placed at finite radii. I.e., near-field compensation compensates for the fact real loudspeakers cannot be placed at the infinite reference radius of Gerzonic Ambisonics.
NOTE: The Ambisonic Toolkit's \FOA set observes this convention.
near-field controlled (NFC or NFCtrl): Characterizing the synthesis or control of a soundfield with near-field properties. Implemnted via radial filtering. The explicit use of the term control is preferred to avoid confusion with the classic Gerzonic use of the term near-field compensated.
NOTE: The Ambisonic Toolkit's \HOA sets observes this convention.
near-field effect (NFE): See near-field and near-field controlled.
operation (op): Ambisonic Toolkit designation indicating the processing domain of an Ambisonic signal set transform: \matrix or \kernel.
panning law: Algorithm for generating phantom imaging.
particle velocity: Vector quantity specifying the velocity of a particle in a medium as it transmits a wave. Ambisonic components of AL degree ℓ = 1 are proportional to particle velocity. See Particle velocity.
planewave: A travelling wave with an infinite radial component.
radial filter: Transform modifying the radial encoding of an Ambisonic signal. Radial filtering is required to implement the near-field effect.
reactive: Describes the imaginary, in quadrature, part of a complex soundfield. See also active.
reference radius: Encoding radius where all modal components are real. See also basic and basic wave.
sectoral modes: Spherical modes where AL degree and AL index are related ℓ = |m|. These modes encode azimuth. See Visualization of the spherical harmonics and Sectorial Harmonic.
set: Ambisonic Toolkit designation indicating Ambisonic order and encoding format. E.g., \FOA, \HOA3.
sound intensity: Vector quantity specifying sound power per unit area. See Sound intensity.
sound pressure: Quantity specifying the local pressure deviation caused by a sound wave. The Ambisonic component of AL degree ℓ = 0 is proportional to sound pressure. See Sound pressure.
soundfield: Region of an elastic medium containing sound waves. See Sound fields.
soundfield kernel composition: An idiomatic composition strategy addressing the holistic problem of creatively controlling a complete soundfield for aesthetic purposes. The Ambisonic Toolkit is designed to facilitate this paradigm.
spherical coefficient: Real or complex scalar applied to encode a signal set into the spherical domain. See spherical harmonic.
spherical design: Minimal equal-weight quadrature on S^d. See Spherical design.
spherical domain: Information represented in terms of spherical basis functions. See spherical harmonics.
spherical harmonics (SH): A complete set of orthogonal, Fourier basis functions on the sphere. For Ambisonics, a set of real form harmonics truncated to a highest Associated Legendre degree, i.e., a given Ambisonic order, encodes a soundfield. See Spherical harmonics.
spherical modes: See spherical harmonics.
spherical wave: A travelling wave with a finite radial component, i.e., a point source.
standing wave: A stationary wave.
tesseral modes: Spherical modes not included as sectoral or zonal, encoding both azimuth and elevation. See Visualization of the spherical harmonics and Tesseral Harmonic.
transform: Modify a spherical domain signal in the spherical domain.
travelling wave: A propagating, incidental wave arriving from some direction. A travelling wave has a look direction.
type: Ambisonic Toolkit soundfield operation designation. E.g., \encode, \xform, \decode.
velocity localisation vector (rV): Vector quantity offering an estimate of the perceived localisation of a phantom source at low frequency, predicting imaging up to around 1.5 kHz. Can be found as the real part of acoustic admittance, the active acoustic admittance.
zonal modes: Spherical modes where AL index m = 0. These modes encode elevation. See Visualization of the spherical harmonics and Zonal Harmonic.

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