Immersive Audio Glossary

Auro3D
A three-dimensional audio technology that creates an immersive soundscape by adding vertical sound layers (height and overhead) on top of traditional surround sound, using unique height speakers to make sounds feel like they’re coming from around and above you, enveloping the listener in a hemisphere of sound for a more realistic, “being there” experience.

3D Audio
A broad term for any audio technology or experience that creates sound perceived as coming from multiple positions in three-dimensional space, enhancing immersion. It includes binaural headphone renders, object-based mixes, and multichannel speaker arrays.

ADM BWF (Audio Definition Model Broadcast Wave Format)
A standardized file format embedding immersive audio metadata and audio files, particularly for Dolby Atmos content delivery and localization. ADM metadata defines object positions, beds, and mix presentations within a Broadcast Wave Format container.

Ambisonics
A spherical surround sound format capturing and reproducing sound from all directions (horizontal and vertical), widely used in VR and adaptable to various playback setups. Ambisonics files come in orders (e.g., first-, second-order) that dictate spatial resolution.

Audio Elements (IAMF)
Within the Immersive Audio Model and Formats (IAMF), these are units of audio content such as channel-based tracks or scene-based ambisonics, managed together with metadata for rendering.

Audio Objects
Discrete sounds treated as independent “objects” with three-dimensional positional metadata (X, Y, Z). They can move dynamically in a 3D soundfield and are a core concept in object-based immersive audio systems like Dolby Atmos.

Auro-Codec
A proprietary codec at the heart of Auro-3D’s encoding and decoding pipeline, compressing immersive audio with full fidelity including height channel data embedded in the PCM carrier.

Auro-Matic
Auro-3D’s intelligent upmixing algorithm that converts legacy mono, stereo, or surround sound material into immersive 3D audio, adapting to speaker layouts.

AuroMax
An extended format within Auro-3D that divides channels into precise “zones” for enhanced spatial accuracy, blending channel- and object-based techniques.

Bed Audio
Traditional fixed multichannel tracks (e.g., 5.1 or 7.1) that form the ambient foundation of immersive mixes, especially within Dolby Atmos. Bed channels correspond to specific speaker placements.

Binaural Audio / Rendering
A headphone-based spatial audio technique simulating how human ears perceive sound in 3D space via Head-Related Transfer Functions (HRTFs), creating an “out-of-head” immersive experience.

Binaural Settings: Off, Near, Mid, Far
Settings in Dolby Atmos Renderer headphone monitoring modes defining the perceived distance of sound objects:

• Off: Stereo downmix without binaural spatialization

• Near: Sounds appear close around the head

• Mid: Balanced spatial distance typical for mixing

• Far: Sounds rendered to seem distant, enhancing depth
  LFE channel is always Off for binaural.

Channel-Based Audio
Audio format where signals map directly to fixed loudspeaker channels (e.g., stereo, 5.1, 7.1). It contrasts with object-based or scene-based audio and remains a core part of many immersive formats (like Auro-3D).

Digital Audio Workstation (DAW)
Software tools for recording, editing, and mixing audio. Modern DAWs often include specific features or plugins to manage beds, objects, and metadata for immersive formats like Dolby Atmos and Ambisonics.

Dolby Atmos Music Assembler
Software that packages audio beds, objects, and mix metadata into ADM BWF files compliant with Dolby Atmos music delivery specifications for streaming and distribution.

Dolby Atmos Renderer
A software application that processes and renders Dolby Atmos mixes by combining bed audio and object metadata. It supports output to speaker arrays and binaural headphone playback with features like dynamic binaural rendering, trim controls, spatial coding, and downmixing.

Downmix & Trim Control (Dolby Atmos)

• Trim: Adjusts gain of objects and beds during monitoring or mastering without altering metadata.

• Downmix: Automated folding of multichannel immersive mixes to fewer channels (e.g., stereo) preserving mix balance for non-immersive playback.

Dynamic Head Tracking
Motion-tracking technology that adjusts spatial audio rendering in real time to maintain perceived sound source positioning relative to listener head movements, enhancing realism in headphones or VR.

Eclipsa Audio
Eclipsa Audio is an open-source, royalty-free 3D spatial audio technology developed by Samsung and Google, based on the Alliance for Open Media’s (AOM) Immersive Audio Model and Formats (IAMF) standard, aiming to provide immersive sound experiences for everyday devices, from TVs and soundbars to headphones, by allowing creators to craft detailed soundscapes without licensing fees. It functions as a container, combining traditional channel-based audio with scene-based formats to create dynamic, 360-degree sound that adapts to different playback environments.

Head-Related Transfer Function (HRTF)
A mathematical model capturing how sound waves are filtered by the anatomy of the listener’s head and ears before reaching the eardrum. It’s fundamental for binaural spatial audio.

Height Channels
Loudspeakers or virtual sources positioned above the listener to add vertical spatial cues, crucial for true 3D immersive audio formats like Dolby Atmos, Auro-3D, and DTS:X.

IAMF (Immersive Audio Model and Formats)
An open-source audio container specification underlying Eclipsa Audio, supporting codec-agnostic storage of immersive audio elements and rich metadata for rendering and customization.

Immersive Audio
All audio techniques and technologies that create a convincing 3D sound environment around and above the listener, including object-based mixing, Ambisonics, binaural rendering, and upmixing.

Interaural Level Difference (ILD)
The difference in sound pressure level reaching each ear, used by the brain to localize sound sources horizontally.

Interaural Time Difference (ITD)
The difference in arrival time of a sound between ears, another key cue for horizontal sound localization.

LFE (Low-Frequency Effects) Channel
A dedicated, band-limited audio channel (typically below 120 Hz) designed for deep, powerful low-frequency sounds, such as explosions or bass effects.

• Usually routed to a subwoofer speaker

• Has 10 dB more output headroom than main channels

• Intended for special effects, not music or dialogue

• Exists as a separate effects channel unique to surround sound and immersive formats like 5.1, 7.1, and Atmos configurations

• Mixers should ensure the LFE contains unique low-frequency content, not replicated from other channels, to avoid phase issues in downmixes

Open Source
Software or technology with publicly available source code that can be freely used, modified, and shared. Examples include IAMF and Eclipsa Audio.

Passthrough Audio
Audio signals routed through an immersive system without additional spatial processing (such as HRTF filtering), often for music beds or UI sounds not needing spatialization.

Panning
Positioning a sound within the spatial soundfield. In immersive audio, panning extends from traditional horizontal placement to full 3D positioning including height.

Re-renders
The real-time decoding or rendering of one immersive master mix into different speaker configurations or headphone formats, allowing flexible playback environments from a single source.

Soundfield
The spatial distribution of sound energy in an environment or recording, describing how sound waves propagate and interact within space, foundational for immersive audio mixing.

Spatial Audio
Synonymous with immersive or 3D audio, it refers especially to precise positioning and movement of sounds in 3D space, giving an authentic sense of presence.

Spatial Coding
A bitrate optimization technique used in Dolby Atmos that groups close-by objects into aggregate “virtual” objects, preserving spatial cues while reducing data for streaming.

Speaker / Channel / Monitoring Conventions

“.1” denotes the LFE channel.

Trim & Downmix Control (Dolby Atmos)
Allows gain tweaking and automatic format downmixing preserving mix intent on non-immersive playback systems.

Upmixing
Conversion from stereo, mono, or traditional surround formats into immersive audio by generating additional spatial and height information.

Virtual Soundstage
The perceptual 3D sound environment created by spatial audio technologies, where sounds appear “outside the head” especially in headphone listening.

Voice Of God (VOG) Channel
An optional overhead speaker directly above the listening position (common in Auro 10.1+ formats), adding a distinct vertical sound layer used for dramatic effects.

Learn more about How Immersive Audio will Transform your Career