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# Spatial Mixing

Define environmental characteristics that determine how sound plays in your app’s 3D soundscape.

## Discussion

Spatial mixing refers to the process by which PHASE emits one or more simultaneous sounds in 3D space and layers in optional environmental effects. For a walkthrough that demonstrates spatial mixing, see [Playing sound from a location in a 3D scene](/documentation/PHASE/playing-sound-from-a-location-in-a-3d-scene).

## Topics

### Setup

[`class PHASESpatialMixerDefinition`](/documentation/PHASE/PHASESpatialMixerDefinition)

An audio-layering object that produces environmental effects and plays sound with a 3D position and orientation.

### Sound Reflections and Resonance

[`class PHASESpatialPipeline`](/documentation/PHASE/PHASESpatialPipeline)

An object that specifies the volume of optional environmental effects.

[`class PHASESpatialPipelineEntry`](/documentation/PHASE/PHASESpatialPipelineEntry)

An audio layer with an adjustable volume for a spatial mixer’s output.

[`struct PHASESpatialCategory`](/documentation/PHASE/PHASESpatialCategory)

Sound resonance effects for spatial mixing.

[`struct Flags`](/documentation/PHASE/PHASESpatialPipeline/Flags-swift.struct)

Sound resonance options for a spatial pipeline.

### Distance Modeling

[`class PHASEGeometricSpreadingDistanceModelParameters`](/documentation/PHASE/PHASEGeometricSpreadingDistanceModelParameters)

An object that dissipates sound frequencies over distance.

[`class PHASEEnvelopeDistanceModelParameters`](/documentation/PHASE/PHASEEnvelopeDistanceModelParameters)

A graph of points and curves that shapes the volume of a sound over distance.

[`class PHASEDistanceModelFadeOutParameters`](/documentation/PHASE/PHASEDistanceModelFadeOutParameters)

A distance over which the framework fades out sound.

[`class PHASEDistanceModelParameters`](/documentation/PHASE/PHASEDistanceModelParameters)

A base class for a sound’s rate of change over distance.

### Sound Directivity

[`class PHASECardioidDirectivityModelParameters`](/documentation/PHASE/PHASECardioidDirectivityModelParameters)

An object that directs sound in a heart-shaped curve surrounding a sound source.

[`class PHASECardioidDirectivityModelSubbandParameters`](/documentation/PHASE/PHASECardioidDirectivityModelSubbandParameters)

A data set that projects sound of a certain frequency outward in the shape of a heart.

[`class PHASEConeDirectivityModelParameters`](/documentation/PHASE/PHASEConeDirectivityModelParameters)

An object that directs sound in a cone-shaped curve that extends from a sound source.

[`class PHASEConeDirectivityModelSubbandParameters`](/documentation/PHASE/PHASEConeDirectivityModelSubbandParameters)

A data set that projects sound of a certain frequency outward in the shape of a cone.

[`class PHASEDirectivityModelParameters`](/documentation/PHASE/PHASEDirectivityModelParameters)

A base class for objects that direct sound.


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