User’s Guide¶

Spatialize an event¶

To spatialize an event:

In the Actor-Mixer Hierarchy, select the sound object you want to spatializer.
Click the Effects tab.
Right-click in the Effects list, then click Add Effect > Steam Audio Spatializer > Default (Custom).

Steam Audio will apply HRTF-based binaural rendering to the event, using default settings. You can control many properties of the spatialization using the Steam Audio Spatializer effect, including occlusion, reflections, and more.

Apply distance falloff¶

You can continue to use Wwise’s built-in tools for controlling distance attenuation of your sound objects, including using RTPC curves to drive the attenuation from the game engine.

As an alternative, you can also use Steam Audio’s physics-based distance attenuation. For more information, see Steam Audio Spatializer.

Apply frequency-dependent air absorption¶

You can continue to use Wwise’s built-in tools for applying distance-dependent low-pass filters and high-pass filters to your sound objects, including using RTPC curves to drive the filters from the game engine.

As an alternative, you can also use Steam Audio’s air absorption. For more information, see Steam Audio Spatializer.

Specify a source directivity pattern¶

You can configure a source that emits sound with different intensities in different directions. For example, a megaphone that projects sound mostly to the front. To do this:

Select the sound object in the Actor-Mixer Hierarchy.
Make sure a Steam Audio Spatializer effect is added to its effect list.
Click the Edit button in the row corresponding to the Steam Audio Spatializer effect.
Set Directivity to Simulation-Defined.
Use the Dipole Weight and Dipole Power sliders to control the directivity pattern.

For more information, see Steam Audio Spatializer.

Use a custom HRTF¶

You (or your players) can replace Steam Audio’s built-in HRTF with any HRTF of your choosing. This is useful for comparing different HRTF databases, measurement or simulation techniques, or even allowing players to use a preferred HRTF with your game or app.

Steam Audio loads custom HRTFs from SOFA files. These files have a .sofa extension.

Note

The Spatially-Oriented Format for Acoustics (SOFA) file format is defined by an Audio Engineering Society (AES) standard. For more details, click here.

Custom HRTFs are loaded and set by the game engine. No special configuration is needed within Wwise.

Follow the instructions in the Steam Audio Unity integration documentation to specify custom HRTFs.

In the game engine, use iplHRTFCreate to load one or more SOFA files.
Call iplWwiseSetHRTF to specify the HRTF to use for spatialization.

Warning

The SOFA file format allows for very flexible ways of defining HRTFs, but Steam Audio only supports a restricted subset. The following restrictions apply (for more information, including definitions of the terms below, click here):

SOFA files must use the SimpleFreeFieldHRIR convention.
The Data.SamplingRate variable may be specified only once, and may contain only a single value. Steam Audio will automatically resample the HRTF data to the user’s output sampling rate at run-time.
The SourcePosition variable must be specified once for each measurement.
Each source must have a single emitter, with EmitterPosition set to [0 0 0].
The ListenerPosition variable may be specified only once (and not once per measurement). Its value must be [0 0 0].
The ListenerView variable is optional. If specified, its value must be [1 0 0] (in Cartesian coordinates) or [0 0 1] (in spherical coordinates).
The ListenerUp variable is optional. If specified, its value must be [0 0 1] (in Cartesian coordinates) or [0 90 1] (in spherical coordinates).
The listener must have two receivers. The receiver positions are ignored.
The Data.Delay variable may be specified only once. Its value must be 0.

Model occlusion by geometry¶

You can configure an event to be occluded by scene geometry. To do this:

Select the sound object in the Actor-Mixer Hierarchy.
Make sure a Steam Audio Spatializer effect is added to its effect list.
Click the Edit button in the row corresponding to the Steam Audio Spatializer effect.
Set Occlusion to Simulation-Defined.

You must now configure your game engine to enable occlusion simulation for this event.

Select the GameObject containing the AkGameObj component.
Make sure a Steam Audio Source component is attached to it.
In the Inspector, check Occlusion.

Steam Audio will now use raycast occlusion to check if the source is occluded from the listener by any geometry. This assumes that the source is a single point. You can also model sources with larger spatial extent. For more information, refer to the Steam Audio Unity integration documentation.

Whenever you create a Wwise Game Object corresponding to a sound source, create a corresponding IPLSource object.
Bind the IPLSource to its corresponding AkGameObjectID by calling iplWwiseAddSource.
Add the IPLSource to your IPLSimulator object using iplSourceAdd, as usual.
Call iplSimulatorRunDirect to run occlusion simulations. The Steam Audio Wwise integration will automatically use the latest simulated occlusion parameter values.

You can also explicitly control occlusion manually or via scripting. For more information, see Steam Audio Spatializer.

Model transmission through geometry¶

You can configure an event to be transmitted through occluding geometry, with the sound attenuated based on material properties. To do this:

Select the sound object in the Actor-Mixer Hierarchy.
Make sure a Steam Audio Spatializer effect is added to its effect list.
Click the Edit button in the row corresponding to the Steam Audio Spatializer effect.
Make sure Occlusion is set to Simulation-Defined, then set Transmission to Simulation-Defined.

You must now configure your game engine to enable transmission simulation for this event.

Select the GameObject containing the AkGameObj component.
Make sure a Steam Audio Source component is attached to it.
In the Inspector, make sure Occlusion is checked, then check Transmission.

Steam Audio will now model how sound travels through occluding geometry, based on the acoustic material properties of the geometry.

Whenever you create a Wwise Game Object corresponding to a sound source, create a corresponding IPLSource object.
Bind the IPLSource to its corresponding AkGameObjectID by calling iplWwiseAddSource.
Add the IPLSource to your IPLSimulator object using iplSourceAdd, as usual.
Call iplSimulatorRunDirect to run occlusion and transmission simulations. The Steam Audio Wwise integration will automatically use the latest simulated occlusion and transmission parameter values.

You can also control whether the transmission effect is frequency-dependent, or explicitly control transmission manually or via scripting. For more information, see Steam Audio Spatializer.

Model reflection by geometry¶

You can configure an event to be reflected by surrounding geometry, with the reflected sound attenuated based on material properties. Reflections often enhance the sense of presence when used with spatial audio. To do this:

Select the event.
Make sure a Steam Audio Spatializer effect is added to its effect list.
Click the Edit button in the row corresponding to the Steam Audio Spatializer effect.
Enable Reflections.

You must now configure your game engine to enable reflections simulation for this event.

Select the GameObject containing the AkGameObj component.
Make sure a Steam Audio Source component is attached to it.
In the Inspector, check Reflections.

Steam Audio will now use real-time ray tracing to model how sound is reflected by geometry, based on the acoustic material properties of the geometry. You can control many aspects of this process, including how many rays are traced, how many successive reflections are modeled, how reflected sound is rendered, and much more. Since modeling reflections is CPU-intensive, you can pre-compute reflections for a static sound source, or even offload the work to the GPU. For more information, refer to the Steam Audio Unity integration documentation.

Whenever you create a Wwise Game Object corresponding to a sound source, create a corresponding IPLSource object.
Bind the IPLSource to its corresponding AkGameObjectID by calling iplWwiseAddSource.
Add the IPLSource to your IPLSimulator object using iplSourceAdd, as usual.
Call iplSimulatorRunReflections to run reflection simulations. The Steam Audio Wwise integration will automatically use the latest simulated reflection parameter values.

For more information, see Steam Audio Spatializer.

Apply physics-based reverb to a mixer bus¶

You can also use ray tracing to automatically calculate physics-based reverb at the listener’s position. Physics-based reverbs are directional, which means they can model the direction from which a distant echo can be heard, and keep it consistent as the player looks around. Physics-based reverbs also model smooth transitions between different spaces in your scene, which is crucial for maintaining immersion as the player moves. To set up physics-based reverb:

In Wwise, select the Auxiliary Bus to which you want to add the reverb effect.
Make sure a Steam Audio Reverb effect is added to its effects list.
Add a send from one or more sound objects to the bus containing the Steam Audio Reverb effect. For more information, see the Wwise documentation.

You must now configure your game engine to enable reverb simulation.

Select the AkAudioListener.
Make sure a Steam Audio Listener component is attached to it.
In the Inspector, check Apply Reverb.

Steam Audio will now use real-time ray tracing to simulate physics-based reverb. You can control many aspects of this simulation, including how many rays are traced, the length of the reverb tail, whether the reverb is rendered a convolution reverb, and much more. Since modeling physics-based reverb is CPU-intensive, you can (and typically will) pre-compute reverb throughout your scene. You can even offload simulation as well as rendering work to the GPU. For more information, refer to the Steam Audio Unity integration documentation.

Call iplSimulatorRunReflections to run reflection simulations for a source located at the listener position.
Call iplWwiseSetReverbSource to specify the IPLSource used to simulate reverb.

For more information, see Steam Audio Reverb.

Model sound paths from a moving source to a moving listener¶

You may want to model sound propagation from a source to the listener, along a long, complicated path, like a twisting corridor. The main goal is often to ensure that the sound is positioned as if it’s coming from the correct door, window, or other opening. This is known as the pathing or portaling problem.

While you can solve this by enabling reflections on an event, it would require too many rays (and so too much CPU) to simulate accurately. Instead, you can use Steam Audio to bake pathing information in a probe batch, and use it to efficiently find paths from a moving source to a moving listener. To do this:

Select the event.
Make sure a Steam Audio Spatializer effect is added to its effect list.
Click the Edit button in the row corresponding to the Steam Audio Spatializer effect.
Enable Pathing.

You must now configure your game engine to enable reflections simulation for this event.

Make sure that pathing information is baked for one or more probe batches in your scene. For more information, refer to the Steam Audio Unity integration documentation.
Select the GameObject containing the AkGameObj component.
Make sure a Steam Audio Source component is attached to it.
Check Pathing.

You can control many aspects of the baking process, as well as the run-time path finding algorithm. For more information, refer to the Steam Audio Unity integration documentation.

Whenever you create a Wwise Game Object corresponding to a sound source, create a corresponding IPLSource object.
Bind the IPLSource to its corresponding AkGameObjectID by calling iplWwiseAddSource.
Add the IPLSource to your IPLSimulator object using iplSourceAdd, as usual.
Call iplSimulatorRunPathing to run pathing simulations. The Steam Audio Wwise integration will automatically use the latest simulated pathing parameter values.

For more information, see Steam Audio Spatializer.