What spatial audio is and is not
Spatial audio is sound that has been designed to exist in three-dimensional space around the listener. When it is working correctly, a visitor in an immersive gallery installation perceives sound as coming from specific locations in the room, moving through the space, emerging from objects, or receding into distance. This perception is distinct from standard stereo or multichannel audio, which places sound within an imagined frontal plane rather than in the ambient space surrounding the listener.
Spatial audio is not simply multichannel sound. Playing eight separate audio channels from eight separate speakers is not the same as designing a spatialised sound environment. The difference is in the mixing and decoding process: spatial audio formats encode position, movement, and depth information that the playback system decodes and resolves into speaker positions. Without the decode stage, multichannel audio is just multiple mono sources placed around the room.
Spatial audio formats and when to use them
Ambisonics is the most commonly used spatial audio format for gallery installations because of its flexibility: the content is encoded in a format-agnostic way (B-format) and then decoded for whatever speaker configuration exists in the physical space. This means an Ambisonic mix can be decoded for a four-speaker horizontal array, an eight-speaker cube, or a large irregular speaker array in an architectural space without re-mixing the content for each configuration. For cultural institutions with irregular or architecturally specific spaces, this flexibility is practically valuable.
Object-based audio formats such as Dolby Atmos and MPEG-H provide a different approach: individual audio objects are positioned in 3D space as metadata, and the playback system renders them to the available speaker configuration in real time. These formats are more familiar from cinema and consumer electronics contexts and are increasingly used for gallery work, particularly in large-scale installations where precise object positioning at the upper end of the frequency range is important. They require specific and sometimes expensive rendering hardware compared to Ambisonic decoders.
- ✓ Confirm the spatial audio format with the artist before the speaker system is specified: the system design follows from the format, not the other way around.
- ✓ Provide the artist with the acoustic measurements of the physical space before the audio is mixed.
- ✓ Allow time in the installation schedule for the artist to experience the spatial decoding in the actual room and make adjustments.
- ✓ Confirm the playback system can reliably trigger and loop the audio in synchronisation with any visual content.
An artist who has created a spatial audio work in their studio on a binaural headphone mix will hear their work differently for the first time in a physical installation. This is expected and should be planned for. The integration session where the spatial decoding is adjusted to the actual room is not an optional polish stage. It is when the work becomes what the artist intended it to be.
Room acoustics and their impact on spatial design
Gallery spaces are acoustically challenging for spatial audio in a specific and consistent way: they tend to have long reverb times, reflective surfaces, and potentially damaging interference patterns from parallel walls. Spatial audio in a room with a two-second reverb time has its directional information blurred by the room's acoustic tail. A sound designed to come from a specific location at three metres becomes a diffuse ambient presence that has no clear point of origin from any position in the room.
Addressing this requires either acoustic treatment to reduce the reverb time to a level that supports the spatial design (typically below one second for close-proximity perceptual effects), or a spatial audio design that works with the room's reverberant characteristics rather than against them. Some artists deliberately design work for reverberant architectural spaces and factor the acoustic tail into the compositional approach. Others need a treated acoustic environment to achieve their creative intent. The production team needs to understand which is the case before specifying the system or recommending acoustic treatment.
Designing a spatial audio system for a gallery
A spatial audio system for a gallery installation starts with the room geometry and the artist's creative intent. Speaker positions are derived from the spatial design and the acoustic characteristics of the space before any hardware is selected. Sub-bass speakers for low-frequency spatial effects, mid-range speakers for speech and primary frequency content, and any height or overhead elements are specified separately and positioned according to the decoding geometry required by the chosen format.
Power and cabling for a multi-speaker spatial system in a gallery needs careful planning around the building's infrastructure and the conservation requirements of the space. Speaker placement near walls or near collection objects may be constrained. Free-standing speaker structures need to be structurally stable and not present a hazard to visitors. Cable routes from the amplifiers and processing system to each speaker position need to be clean, safe, and appropriate for the gallery environment. All of these are solvable with adequate planning time. None of them are solvable in the hours before opening.
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Frequently asked questions
What is the minimum number of speakers needed for a spatial audio installation?
Four speakers in a horizontal plane provide a basic spatial field that a visitor can perceive as extending around them. Eight speakers (cube configuration) add height. Larger, more complex arrays provide more precise spacialisation and are appropriate for larger spaces. The minimum specification depends on the creative intent and the scale of the space.
Can spatial audio be delivered through headphones in a gallery?
Yes, through binaural rendering on headphones. This provides spatial perception through head-related transfer function processing and avoids the room acoustic challenges of loudspeaker-based systems. However, it requires visitors to wear headphones, which changes the nature of the gallery experience and requires wireless infrastructure for mobility. Both approaches have appropriate applications.
How do we synchronise spatial audio with visual content in an immersive installation?
Timecode synchronisation is the standard method for multi-channel AV installations. A SMPTE timecode signal generated by the media server or a master clock is shared with the audio playback system, locking them to a common reference. This ensures the spatial audio and visual content remain in sync through loop transitions, and that any programmatic changes to the playback schedule affect both channels identically.