The Ultimate Spatial Audio Glossary: Every Term you Need to Know

What Is Spatial Audio?

Spatial Audio

Audio designed to communicate where a sound exists in three-dimensional space, including direction, elevation, distance, and movement.

Immersive Audio

Audio designed to surround and envelop the listener, potentially including sound above and below as well as around them.

3D Audio

A general term for audio reproduction that represents sound in three dimensions.

Surround Sound

Multichannel audio designed to surround the listener, traditionally using speaker layouts such as 5.1 or 7.1.

Sound Field

The spatial distribution of sound energy around a listener or recording position.

Soundfield Recording

A recording designed to preserve information about the surrounding acoustic environment rather than simply capturing isolated sound sources. Our ambisonic sound libraries are built from soundfield recordings captured this way.

Immersive Soundscape

A spatial recording or designed environment intended to place the listener inside a three-dimensional sonic scene.

Channel-Based, Object-Based & Scene-Based Audio

One of the most important distinctions in spatial audio is how the audio information itself is represented.

Channel-Based Audio

Channel-Based Audio — Audio in which each channel is associated with a predefined speaker position. Examples include stereo, 5.1 and 7.1. The audio is mixed for a particular channel configuration rather than describing individual sounds as independently positioned objects.

Object-Based Audio

Object-Based Audio (OBA) — Audio in which individual sounds are accompanied by metadata describing their position or other properties. Instead of permanently assigning a sound to a particular speaker, the renderer determines how that sound should be reproduced for the available playback system.

• Audio Object — An individual sound element represented separately from the speaker layout.
• Object Metadata — Information describing properties of an audio object, such as position, movement, size, or other rendering parameters.
• Object Renderer — A system that interprets object metadata and distributes audio appropriately across the available playback system.
• Bed — A fixed multichannel foundation used alongside audio objects in some immersive-audio systems.
• Bed + Objects — A production approach combining fixed channel-based material with independently positioned audio objects.

Scene-Based Audio

Scene-Based Audio — Audio that represents a sound field independently from a specific loudspeaker layout. Ambisonics is the best-known example. A scene-based recording can be decoded or rendered for different speaker arrangements or headphone playback systems. Our guide, Inside the Sound Sphere: Ambisonic Recording Guide, walks through this in detail.

Dolby Atmos

Dolby Atmos — An immersive-audio format that combines channel-based beds with audio objects containing positional metadata. A Dolby Atmos renderer adapts the content to the available playback system.

Dolby Atmos is used in cinema, television, streaming, games, music, headphones, home theater, and other applications. We cover why this shift matters in Beyond Stereo: Redefining Immersive Sound.

• Dolby Atmos Music — Dolby Atmos productions specifically created for music playback.
• Dolby Atmos for Cinema — The cinema implementation of Dolby Atmos.
• Dolby Atmos Renderer — Professional software used to monitor, process, and render Dolby Atmos content.
• Dolby Atmos Bed — A fixed multichannel component of an Atmos mix.
• Dolby Atmos Object — An audio element whose position is described using metadata and interpreted by the Atmos renderer.
• Dolby Atmos Binaural Rendering — Processing used to reproduce Atmos spatial information through headphones.
• Dolby Atmos Upmixing — Converting stereo or surround content into an Atmos bed-and-object mix. If you need this done for an existing project, see our immersive audio upmixing services.

DTS:X

DTS:X — An object-based immersive-audio format developed by DTS for cinema, home theater, and other applications. DTS:X can use audio objects and metadata to adapt a mix to different speaker configurations.

DTS Headphone:X — DTS technology designed to reproduce spatial audio through headphones.

Auro-3D

Auro-3D — A three-dimensional multichannel audio format that adds height information above a conventional surround-sound layer. It has been used in cinema, home entertainment, music, and other immersive applications.

Auro-Max — Auro Technologies' larger-scale extension of Auro-3D, designed for bigger cinema and large-venue speaker configurations beyond the standard Auro-3D layer count.

MPEG-H 3D Audio

MPEG-H 3D Audio — An international audio standard supporting immersive and interactive audio. It can represent channel-based, object-based, and scene-based audio.

MPEG-H Audio — The broader MPEG-H audio technology family used for advanced broadcast and immersive-audio applications.

IAMF

IAMF (Immersive Audio Model and Formats) — An open specification for representing and delivering immersive audio. IAMF can support different types of immersive content, including channel-based, object-based, and scene-based representations. It is designed to provide an interoperable way of storing, distributing, and rendering immersive audio.

Eclipsa Audio

Eclipsa Audio — An open immersive-audio technology based on the IAMF ecosystem. It is designed to support spatial audio creation, distribution, and playback across compatible systems.

Eclipsa Audio is particularly relevant to the development of open immersive-audio workflows and next-generation media formats. We go deeper on this in Eclipsa Audio: Why It Could Be the Future of Spatial Sound, and compare it directly against the incumbent format in Eclipsa Audio vs. Dolby Atmos: The Format Fight Sound Designers Can't Ignore.

OAR

OAR (Open Audio Renderer) — An open-source renderer associated with the AOMedia immersive-audio ecosystem. OAR is designed to provide an open implementation for rendering immersive audio content.

Delivery Codecs & Broadcast Standards

Immersive-audio formats like Atmos and DTS:X still need a codec to actually carry them through a broadcast, streaming, or disc pipeline. This is a distinct layer worth knowing.

E-AC-3 JOC (Joint Object Coding)

The method Dolby uses to fold Atmos object audio into a standard Dolby Digital Plus (E-AC-3) bitstream, which is how most streaming services (Netflix, Apple Music, Disney+, etc.) deliver Atmos.

Dolby TrueHD

A lossless codec used to carry Dolby Atmos on Blu-ray and other high-bitrate physical or file-based delivery.

AC-4

Dolby's next-generation audio codec, built for broadcast and streaming delivery of immersive and personalized audio, including Atmos.

USAC (Unified Speech and Audio Coding)

The underlying MPEG codec that MPEG-H 3D Audio is built on top of.

SAOC (Spatial Audio Object Coding)

An earlier MPEG technology for efficiently coding audio objects, a conceptual precursor to modern object-based delivery.

NGA (Next Generation Audio)

An umbrella term broadcasters use for the family of immersive and personalized audio systems (Dolby AC-4/Atmos, MPEG-H, DTS:X) supported in modern TV delivery.

ATSC 3.0

The North American broadcast standard that supports NGA delivery, enabling immersive and object-based audio in over-the-air television.

LUFS (Loudness Units Full Scale)

The standard unit for measuring perceived loudness. Immersive mixes still need loudness management on delivery, even with height and object channels involved.

Dialogue Normalization

Metadata that tells a playback system how much to adjust overall loudness so dialogue sits at a consistent level across different sources and formats.

Ambisonics

Ambisonics — A scene-based spatial-audio technique that represents a three-dimensional sound field using spherical-harmonic components. Unlike conventional channel-based surround formats, Ambisonics does not inherently depend on a particular speaker layout.

This makes it particularly useful for virtual reality, 360° video, games, spatial field recording, immersive installations, and interactive applications. Our article Beyond 1st Order: Why HOA Is Finally Hitting the Mainstream covers where the format is heading in 2026.

First-Order Ambisonics

FOA (First-Order Ambisonics) — The first level of full-sphere Ambisonic representation. FOA uses four channels to represent the basic components of a three-dimensional sound field.

Higher-Order Ambisonics

HOA (Higher-Order Ambisonics) — Ambisonics using additional spherical-harmonic components to provide greater spatial resolution. Higher orders require more channels.

Second-Order Ambisonics

2OA (Second-Order Ambisonics) — A nine-channel full-sphere Ambisonic representation.

Third-Order Ambisonics

3OA (Third-Order Ambisonics) — A sixteen-channel full-sphere Ambisonic representation. Several of our 3rd-order libraries are recorded and delivered at this resolution.

Fourth-Order Ambisonics

4OA (Fourth-Order Ambisonics) — A twenty-five-channel full-sphere Ambisonic representation.

Ambisonic Order

Ambisonic Order — The order of the spherical-harmonic representation used to describe the sound field. Increasing the order increases the number of channels and can provide greater spatial resolution.

A-Format & B-Format

A-Format — The raw signals produced by the capsules of certain Ambisonic microphones before conversion into an Ambisonic B-Format representation.

B-Format — A representation of an Ambisonic sound field using directional components rather than individual microphone-capsule signals. Our developer's guide to decoding ambisonic audio for VR explains how B-Format gets converted for real-time engines.

W, X, Y, Z — The traditional first-order B-Format components. W represents the omnidirectional component while X, Y, and Z represent directional components.

AmbiX

AmbiX — A widely used Ambisonic interchange convention based on ACN channel ordering and SN3D normalization. AmbiX is commonly encountered in VR, games, spatial-audio software, plugins, and modern Ambisonic workflows.

FuMa

FuMa (Furse-Malham) — An older Ambisonic channel-ordering and normalization convention. FuMa was widely used in earlier first-order Ambisonic systems and remains relevant when working with legacy material.

ACN

ACN (Ambisonic Channel Number) — A standardized numerical ordering system used to identify Ambisonic spherical-harmonic components. ACN is commonly used together with SN3D normalization.

SN3D

SN3D (Schmidt Semi-Normalization) — A normalization convention used to scale spherical-harmonic components in Ambisonic systems. ACN + SN3D is a common convention for modern Ambisonic interchange.

N3D

N3D (Full 3D Normalization) — Another spherical-harmonic normalization convention used in Ambisonics. N3D and SN3D use different scaling factors and should not be treated as interchangeable without the appropriate conversion.

Spherical Harmonics

Spherical Harmonics — Mathematical functions used to represent directional information over a sphere. They provide the mathematical foundation of Higher-Order Ambisonics.

Ambisonic Encoding & Decoding

• Ambisonic Encoder — Software or hardware that converts sound sources or microphone signals into an Ambisonic representation. See our free ambisonic and spatial audio plugins guide for encoder recommendations that won't cost you anything.
• Ambisonic Decoder — Software or hardware that converts Ambisonic signals into loudspeaker feeds or another playback format.
• Ambisonic Panning — Positioning a sound source within an Ambisonic sound field.
• Ambisonic Rotation — Rotating an Ambisonic sound field to match the listener's orientation or camera direction.
• Ambisonic Binaural Rendering — Converting Ambisonic audio into a binaural signal for headphone playback.
• Periphonic Audio — Full three-dimensional spatial audio containing both horizontal and vertical information.
• Horizontal Ambisonics — Ambisonic representation primarily focused on the horizontal plane rather than full three-dimensional elevation.

Binaural Audio

Binaural Audio — Audio designed to reproduce spatial hearing through two channels, normally for headphone playback. Binaural systems attempt to recreate the differences between the signals arriving at the listener's two ears.

Binaural Recording

Recording using two microphones positioned to capture the acoustic experience at the listener's ears.

Binaural Rendering

Processing spatial audio into a two-channel signal intended for headphone reproduction.

Dummy Head

A human-shaped recording system with microphones positioned approximately where the ears would be.

Binaural Microphone

A microphone system designed specifically for binaural recording.

Binaural Monitoring

Checking a spatial mix through a binaural downmix on headphones during production, rather than only on speakers. If you work in Reaper, Cubase, or Ableton, our guide to binaural monitoring across Reaper, Cubase, and Ableton Live covers the setup in each DAW.

HRTF & Spatial Hearing

HRTF (Head-Related Transfer Function)

A measurement or model describing how a person's head, torso, and ears affect sound arriving from different directions. HRTFs are fundamental to headphone-based spatial audio.

HRIR (Head-Related Impulse Response)

The impulse-response representation used to describe a head-related transfer function.

BRIR (Binaural Room Impulse Response)

A binaural impulse response that captures both the listener-related filtering and the acoustic response of a room.

Personalized HRTF

An HRTF measured or modeled specifically for an individual listener.

Personalized Spatial Audio (Ear/Face Scanning)

A consumer implementation of personalized HRTF where a phone camera scans the listener's ears and head shape to generate a custom HRTF profile, as used in some Apple Spatial Audio headphone experiences.

Generic HRTF

An HRTF selected from a general or averaged dataset rather than measured specifically for the listener.

Head Tracking

Technology that tracks the listener's head orientation and updates the spatial audio accordingly.

Head-Locked Audio

Audio that remains fixed relative to the listener's head.

Head-Tracked Audio

Spatial audio that changes in response to the listener's head movement.

Externalization

The perception that a sound reproduced through headphones exists outside the head rather than inside it.

Spatialization & Rendering

Spatializer

Software or hardware that positions sound within a spatial environment.

Spatial Renderer

A system that converts spatial-audio information into signals appropriate for a particular playback system.

Binaural Renderer

A renderer that converts spatial audio into headphone-compatible binaural output.

Panning

Controlling audio levels or other parameters to change the perceived position of a sound.

3D Panning

Panning that includes horizontal direction and vertical elevation.

VBAP (Vector Base Amplitude Panning)

A technique for positioning sounds between loudspeakers using amplitude relationships.

DBAP (Distance-Based Amplitude Panning)

A panning method that uses the distance between a virtual sound source and loudspeakers.

WFS (Wave Field Synthesis)

A spatial-reproduction technique using many loudspeakers to reconstruct aspects of a desired sound field.

Acoustic Ray Tracing

A rendering technique that simulates how sound waves bounce and travel through a virtual space, used by some real-time and headset-based spatial audio engines (including Apple's visionOS) to model realistic reverberation and occlusion.

Convolution Reverb

A reverb technique that applies a captured impulse response (such as a BRIR or RIR) to dry audio, recreating the acoustic character of a real or modeled space.

IR Library (Impulse Response Library)

A collection of recorded or modeled impulse responses used with convolution reverb to place sound in different acoustic spaces.

Rendering Intent / Downmix Coefficients

Metadata or settings that define how an immersive or object-based mix should gracefully collapse to a lower channel count, such as stereo, while preserving the original creative balance as closely as possible.

Upmix

Creating additional channels or spatial information from a source with fewer channels.

Downmix

Converting a multichannel or immersive format into a format with fewer channels. If you need existing stereo assets converted the other way, our immersive audio upmixing service handles this.

Speaker Layouts

• Mono — One audio channel.
• Stereo — Two audio channels, normally Left and Right.
• 2.0 — Two full-range channels without a dedicated LFE channel.
• 2.1 — Left and Right channels plus a dedicated low-frequency channel.
• 5.1 — Five main channels plus one LFE channel.
• 5.1.2 — Five main surround channels, one LFE channel, and two height channels.
• 5.1.4 — Five main surround channels, one LFE channel, and four height channels.
• 7.1 — Seven main channels plus one LFE channel.
• 7.1.2 — Seven main surround channels, one LFE channel, and two height channels.
• 7.1.4 — Seven main surround channels, one LFE channel, and four height channels.
• 9.1.4 — Nine main channels, one LFE channel, and four height channels.
• 9.1.6 — Nine main channels, one LFE channel, and six height channels, used in some higher-end home theater and dedicated Atmos mixing setups.
• 22.2 — A large immersive broadcast configuration consisting of multiple horizontal, height, and overhead channels plus low-frequency channels.
• Height Channels — Channels positioned above the listener to reproduce vertical information.
• Overhead Speakers — Speakers physically positioned above the listener.
• LFE (Low-Frequency Effects) — A dedicated low-frequency channel used in surround and immersive systems.

Spatial-Audio Metadata

Metadata

Information accompanying audio that describes how the audio should be interpreted, positioned, or rendered.

Positional Metadata

Metadata describing the position or movement of a sound source.

ADM (Audio Definition Model)

A standardized metadata framework for describing audio content and its associated spatial information.

ADM BWF

Broadcast Wave Format containing Audio Definition Model metadata.

BWF (Broadcast Wave Format)

A professional extension of the WAV format commonly used in broadcast, post-production, and professional audio workflows.

IAB (Immersive Audio Bitstream)

A standardized representation of immersive audio used in professional media workflows.

IMF IAB

Immersive Audio Bitstream carried within the Interoperable Master Format ecosystem.

Acoustic & Perceptual Terminology

Localization

The listener's perception of where a sound originates.

Azimuth

The horizontal angular position of a sound around the listener.

Elevation

The vertical position of a sound relative to the listener.

Depth

The perceived front-to-back position of a sound.

Distance Perception

The perception of how far away a sound source is.

Direct Sound

Sound traveling directly from a source to the listener.

Early Reflections

Initial reflections arriving shortly after the direct sound.

Reverberation

The collection of reflections that persists after the direct sound.

Room Impulse Response (RIR)

A measurement describing how a room responds acoustically to an impulse.

Diffuse Field

A sound field in which acoustic energy arrives from many directions.

Near Field

The region close to a sound source where acoustic behavior differs from the far field.

Far Field

The region sufficiently distant from a sound source where sound propagation has more predictable directional behavior.

Envelopment

The perceptual sensation of being surrounded by sound.

Immersion

The sensation of being placed inside a sonic environment.

Presence

The perception that a reproduced sound or environment feels immediate and convincing.

ITD (Interaural Time Difference)

The difference in arrival time of a sound at the two ears.

ILD (Interaural Level Difference)

The difference in sound level reaching the two ears.

Interaural Cues

Spatial information created by differences between the signals reaching the listener's two ears.

Doppler Effect

A perceived change in frequency caused by relative motion between a sound source and listener.

Spatial Field Recording

Field Recording

Recording real-world sounds outside a controlled studio environment. Our field team documented this process on location in The 4:00 AM Wakeup Call: Costa Rica Jungle and Mapping the 3D Tropical Field.

Spatial Field Recording

Field recording designed to preserve directional and spatial information. Libraries like Central American Jungle Bioma Vol. I and Ambisonic Experience: Nature & Water are built entirely from this kind of recording.

Ambisonic Microphone

A microphone system designed to capture a spherical sound field. See our complete directory of ambisonic microphone brands covering Rode, Sennheiser, and Zoom, and our Zoom H3 recorder review if you're shopping on a budget.

Tetrahedral Microphone

A four-capsule microphone arrangement commonly used for First-Order Ambisonic recording.

Soundfield Microphone

A microphone system designed to capture directional components of an acoustic sound field.

Multichannel Recording

Recording using multiple discrete audio channels.

Microphone Array

Multiple microphones arranged to capture spatial or directional information.

Coincident Microphone Array

A microphone arrangement in which capsules are positioned very close together to reduce time-of-arrival differences.

Capsule

An individual microphone transducer within a microphone system.

Polar Pattern

A microphone's directional sensitivity to sounds arriving from different directions.

Omnidirectional

A polar pattern designed to capture sound from approximately all directions.

Figure-8 / Bidirectional

A polar pattern sensitive primarily to the front and rear while rejecting the sides.

Phase Coherence

The preservation of consistent phase relationships between multiple audio signals.

VR, AR, XR & 360° Audio

VR Audio

Spatial audio designed for virtual-reality environments.

XR Audio

Spatial audio used in extended-reality applications, including VR, AR, and mixed reality.

AR Audio

Spatial audio integrated with augmented-reality environments.

MR Audio

Spatial audio used in mixed-reality environments combining physical and virtual elements.

360° Audio

Audio designed to correspond with a 360-degree visual environment.

360° Video Audio

Spatial audio synchronized with spherical video.

Ambisonic Video

Video containing an Ambisonic or other spatial-audio track designed to work with a spherical visual environment.

visionOS Audio Ray Tracing

Apple's real-time acoustic ray-tracing approach for spatial audio on Vision Pro, modeling how sound interacts with the physical room around the listener rather than relying solely on static HRTFs.

3DoF (Three Degrees of Freedom)

Interaction based on rotational movement around three axes: pitch, yaw, and roll.

6DoF (Six Degrees of Freedom)

Interaction including three rotational axes and three positional axes. Our article Beyond 1st Order discusses how HOA supports 6DoF experiences.

Interactive Audio

Audio that changes dynamically in response to user actions, movement, or environmental conditions.

Game Audio

Interactive audio created for video games, often using real-time spatialization. See our guide to implementing Ambisonics in Unreal Engine (UE5) for a hands-on walkthrough.

Environmental Audio

Spatial representation of environmental sounds such as weather, wildlife, traffic, interiors, and natural environments.

Diegetic Audio

Sound that exists within the fictional world of a film, game, or immersive experience.

Non-Diegetic Audio

Sound presented to the audience that does not originate within the fictional environment.

Spatial Audio Production

DAW (Digital Audio Workstation)

Software used to record, edit, mix, and process audio.

Spatial Panner

A software interface used to position sound within a spatial environment.

Object Panner

A tool used to position an audio object using spatial metadata.

Renderer Plugin

Software that converts spatial audio into a particular speaker or headphone output. Our guide to free ambisonic and spatial audio plugins lists usable options at no cost.

Monitoring

Listening to audio through a defined playback system during production.

Immersive Monitoring

Monitoring through a speaker or headphone system capable of reproducing spatial audio. See our binaural monitoring guide for Reaper, Cubase, and Ableton Live.

Speaker Calibration

Measurement and adjustment of loudspeakers to achieve consistent playback.

Room Calibration

Measurement and correction of a listening environment.

Reference Layout

A defined speaker configuration used as a reference for mixing or monitoring.

Master File

The final high-quality audio file or package used to create distribution versions.

Interchange Format

A format designed to allow audio and metadata to move between production systems.

Spatial Audio Technologies & Ecosystems

• Apple Spatial Audio — Apple's consumer spatial-audio ecosystem, including support for Dolby Atmos and head-tracked headphone playback.
• Sony 360 Reality Audio — Sony's object-based immersive music format.
• Windows Sonic — Microsoft's spatial-audio technology for Windows and Xbox.
• PlayStation 3D Audio — Sony's spatial-audio technology used by PlayStation systems.
• Steam Audio — A spatial-audio toolkit for games and interactive applications.
• Resonance Audio — Google's spatial-audio technology developed for immersive applications, games, and VR.
• Sennheiser AMBEO — Sennheiser's spatial-audio ecosystem, spanning Ambisonic microphones, binaural recording gear, and Atmos-related production tools.
• Meta 360 Spatial Workstation — A suite of spatial-audio production tools originally developed by Facebook/Meta for 360° video and VR sound design.
• Google Omnitone — An early open-source, web-based Ambisonic decoder that helped bring spatial audio playback to browsers.
• Game Audio Middleware — Software platforms that provide tools for implementing interactive and spatial audio in games.
• Wwise — Audiokinetic's interactive audio middleware widely used in game development and other interactive applications.
• FMOD — Interactive audio middleware used to implement dynamic and spatial audio in games and interactive experiences.
• Unity Audio — The audio system and associated tools available within the Unity game engine.
• Unreal Engine Audio — The audio system and spatial-audio tools available within Unreal Engine. Our step-by-step Ambisonics in Unreal Engine: UE5 guide covers MetaSounds and VR/XR setup.

Important Spatial-Audio Abbreviations

Spatial Audio: A Quick Reference

• Spatial audio is not a single format. It is a broad field encompassing several different approaches.
• Channel-based audio assigns audio to predefined speaker channels.
• Object-based audio separates sounds into objects and uses metadata to describe where those sounds should appear.
• Scene-based audio represents the sound field itself, allowing it to be decoded or rendered for different playback systems.
• Ambisonics is a scene-based approach particularly suited to spherical sound fields, VR, 360° video, interactive applications, and spatial field recording.
• Dolby Atmos and DTS:X are examples of object-based immersive-audio systems.
• Binaural audio is a two-channel representation designed primarily for headphone playback.
• HRTFs provide the acoustic filtering information needed to reproduce directional cues over headphones.
• IAMF, Eclipsa Audio, MPEG-H, and related technologies represent ongoing efforts to standardize immersive-audio storage, distribution, and rendering.
• Delivery codecs like E-AC-3 JOC, Dolby TrueHD, and AC-4 are what actually carry these formats through streaming, disc, and broadcast pipelines.
• Understanding the differences between these systems is essential when recording, mixing, delivering, or reproducing immersive audio.

Frequently Asked Questions