The acoustics features provide spatial cues beyond the direct path HRTF, including reflections and reverb. This creates a sense of space and helps to anchor spatial audio sources into the world.

The Meta XR Audio SDK offers two different Acoustic Models:

The Shoebox Room, which offers a lightweight solution with manual controls of a rectangular room. All components associated with this model are prefixed “MetaXRAudioRoom”.

Acoustic Ray Tracing which offers a more natural audio experience than the Shoebox Room solution and simplifies sound design by automating what are typically more manual processes with intuitive controls. All components associated with this model are prefixed “MetaXRAcoustic”. Acoustic Ray Tracing is implemented entirely in unreal even if you are using Middleware and is fully documented in its own section.

By the end of this document, you’ll be able to:

Setup your project to use Meta XR Audio.

Setup an Audio Source to be spatialized and enter the Meta XR Reflections engine.

Select which acoustic model Meta XR Audio will use for rendering.

Adjust the available parameters for acoustics.

Learn about the specific technical details about every parameter for acoustics.

Prerequisites

Setup the Mixer

Place the MetaXRAudio Reflections effect before the Fader on the Master Bus channel. These parameters will affect all sounds in the project using the MetaXRAudio Source Plugin.

From the main menu, select Window > Mixer.

In the space before the Fader, right-click (Cmd+click on Mac) and select Add Effect > Plug-in Effects > Meta > MetaXRAudio Reflections.

Adding a Meta XR Audio Reflections instance to the FMOD Studio mixer.

This effect contains parameters that directly control the reverb as well as global settings that are shared across all instances of the spatializer.

IMPORTANT: The MetaXRAudio Reflections plugin is shared by all sources. This means the plugin is a singleton and only one instance of this plugin can exist in your FMOD project. If you create more than one instance of MetaXRAudio Reflections in your project, you will experience undefined behavior.

Reflections settings

The following image shows the reverb settings for the spatializer.

The controls on the Meta XR Audio Reflections plugin.

Parameter	Description
Early Reflections Enabled	When enabled, the low order reflections of each audio object will be rendered. When disabled, no object will have it’s lower order reflections rendered.
Reverb Enabled	This enables the late reverbation modelling for all audio objects. When disabled, no reverb will be applied.
Reverb Level (dB)	Use this parameter to adjust the overall level of the reverb relative to it’s acoustically accurate position. A positive value increases the reverb level for all objects and is applied on top of whatever audio object reverb level is specified (see below) and a negative value decreases the reverb level for all audio objects.
Voice Limit	When using the FMOD Studio app, use this parameter to artificially limit the maximum number of sources the reflections plugin can support to experiment with different, more efficient settings and test out your mixer bus voice limits and SFX priorities. This parameter will be used when loading the plug-in to determine how many audio objects to allocate. This means you can use this parameter to tune the CPU and memory consumption of the plugin in-game. Note this also means that if you change the parameter you must save your FMOD project, exit FMOD Studio, and then reopen the project for the change to apply.

Implementation

To adjust your room acoustics you will need to install and use the Meta XR Audio SDK for Unreal Plugin. Make sure to have completed the installation and setup before continuing.

Selecting your Reverb Engine

In order to tell the Meta XR Audio SDK which of the two options to utilize, navigate to Edit > Project Settings > Meta XR Acoustics. Find the Acoustic Model dropdown and selected the desired option. Note that automatic will prefer the Raytraced Acoustics option if the project is setup to use it.

Important: If you would like to use Acoustics, proceed to the documentation specific to that engine. If you prefer to use the lightweight Shoebox Room engine, continue reading on this page to learn about the Room component.

Change Shoebox Room acoustics properties in editor

In your editor, you will need to add a Meta XR Audio Room component to something in the game. It is important to note that you should only have one of these components in your entire game because it is global. If you add multiple of these components, only the most recently added component will function properly and the older components will no longer change the effects.

Adding room component to an actor in Unreal.

Once you have added the component you can adjust the settings directly in the UI.

Change Shoebox Room acoustics properties with Blueprints

If you want the game to programatically change the room acoustics as the game progresses you will need to use the provided Blueprint functions to get and set the parameters of the component. To them to your Blueprint, right click on the Blueprint, uncheck the “Context Sensitive” checkbox and then search for “Get” or “Set” and the name of the parameter you want to change.

Searching for Meta XR Audio Blueprint nodes.

Make sure the Blueprint has access to your Meta XR Audio Room Acoustic Properties instance or create your only instance directly in the Blueprint. Drag the instance of the component onto the Blueprint and connect it to the target of the getter or setter function.

There is also a setter function which combines all the properties into a single Blueprint node called Set Room Acoustic Properties. This simplifies the setting process is you plan to change multiple parameters of the room at once.

Blueprint using the Set Room Acoustic Properties node.

Parameter reference

Property	Description
Lock Position To Listener	If enabled, this keeps the room model centered on the listener (camera). If disabled, then the Room Acoustics component should be positioned in the geometric center of the room in world space (usually, this is the center of the 3D mesh that represents the room). This setting is recommended to be enabled unless your scene is confined to a single room.
Width, Height, Depth	Sets the dimensions of the room model (in meters for Unity and in centimeters for Unreal) used to determine the early reflection and reverb. Width is the x dimension, Height is the y dimension, and Depth is the z dimension. The orientation of transform of the GameObject that this script is attached to defines the orientation of the room’s coordinate system.
Materials	This controls the materials of the shoebox room model. Harder materials reflect more sound and create longer reverb tails. Softer materials shorten the reverb’s response. For a list of materials and their frequency-dependent reflection coefficients, see the table below.
Clutter Factor	Represents how much clutter (i.e. furniture, people, etc.) is in the room that would dampen the response. This parameter creates diffusion and can be used to tame an overly reverberant room. A setting of 0 represents no clutter at all (an empty room), whereas a setting of 1 represents an extremely cluttered room.

Material absorption factors

The following table shows the reflection coefficients for each material for each frequency band.

Material	0-176 Hz	176-775 Hz	775-3408 Hz	3408-22050 Hz
AcousticTile	0.488168418	0.361475229	0.339595377	0.498946249
Brick	0.975468814	0.972064495	0.949180186	0.930105388
BrickPainted	0.975710571	0.98332417	0.978116691	0.970052719
Cardboard	0.590000	0.435728	0.251650	0.208000f
Carpet	0.987633705	0.905486643	0.583110571	0.351053834
CarpetHeavy	0.977633715	0.859082878	0.526479602	0.370790422
CarpetHeavyPadded	0.910534739	0.530433178	0.29405582	0.270105422
CeramicTile	0.99000001	0.99000001	0.982753932	0.980000019
Concrete	0.99000001	0.98332417	0.980000019	0.980000019
ConcreteRough	0.989408433	0.964494646	0.922127008	0.900105357
ConcreteBlock	0.635267377	0.65223068	0.671053469	0.789051592
ConcreteBlockPainted	0.902957916	0.940235913	0.917584062	0.919947326
Curtain	0.686494231	0.545859993	0.310078561	0.399473131
Foliage	0.518259346	0.503568292	0.5786888	0.690210819
Glass	0.655915797	0.800631821	0.918839693	0.92348814
GlassHeavy	0.827098966	0.950222731	0.97460413	0.980000019
Grass	0.881126285	0.507170796	0.131893098	0.0103688836
Gravel	0.729294717	0.373122454	0.25531745	0.200263441
GypsumBoard	0.721240044	0.927690148	0.93430227	0.910105407
Marble	0.990000	0.990000	0.982754f	0.980000f
Mud	0.844084	0.726577	0.794683	0.849737
PlasterOnBrick	0.975696504	0.979106009	0.961063504	0.950052679
PlasterOnConcreteBlock	0.881774724	0.924773932	0.951497555	0.959947288
Rubber	0.950000	0.916621	0.936230	0.950000
Soil	0.844084203	0.634624243	0.416662872	0.400000036
SoundProof	0.0	0.0	0.0	0.0
Snow	0.532252669	0.15453577	0.0509644151	0.0500000119
Steel	0.793111682	0.840140402	0.925591767	0.979736567
Stone	0.980000	0.978740	0.955701	0.950000
Vent	0.847042	0.620450	0.702170	0.799473
Water	0.970588267	0.971753478	0.978309572	0.970052719
WoodThin	0.592423141	0.858273327	0.917242289	0.939999998
WoodThick	0.812957883	0.895329595	0.941304684	0.949947298
WoodFloor	0.852366328	0.898992121	0.934784114	0.930052698
WoodOnConcrete	0.959999979	0.941232264	0.937923789	0.930052698