To simulate the attenuation of objects in Wwise, you can create a series of curves that define a relationship between certain properties in Wwise, such as Volume and Low-Pass Filter, and different drivers, such as the distance between the source and the listener in game.
You can create Attenuation curves for the following drivers:
Distance - The distance between an emitter and the listener. Its value can range from 0 to a max distance value that defines the point where maximum distance attenuation of the object occurs. Since sounds emanate from an omni-directional source, the max distance value creates a spherical radius around each source.
Obstruction - The percentage of obstruction between an emitter game object and its listener. Its value can range from 0 to 100.
Occlusion - The percentage of occlusion between an emitter game object and its listener. Its value can range from 0 to 100.
Diffraction - The percentage of diffraction on a diffraction path between an emitter and its listener. This value is set by Spatial Audio and can range from 0 to 100.
Transmission - The percentage of transmission loss on the transmission path between an emitter and the listener. This value is set by Spatial Audio and can range from 0 to 100.
By default, the attenuation of your object's signal is applied with the Distance Volume curve using a linear interpolation from the source to the max distance. The obstruction and diffraction curves use the project's obstruction curves and the occlusion and transmission curves use the project's occlusion curves.
Although this may work in most cases, specific objects may require more advanced curves. To have more control over the Attenuation curve, you can add control points. These points break up the Attenuation curve so that you can better manage the attenuation of your object.
To create a more detailed and complex positioning curve, you can also define the shape of each curve segment. A curve segment is any part of the curve between two control points. You can choose from a variety of curve shapes, including linear, constant, logarithmic, exponential, and s-curve. For more information on specifying curve shapes and other information about working in the graph view, refer to Getting to Know the Graph View.
You can create Attenuation curves for the following Wwise properties:
Volume - The attenuation or amplitude of the signal routed to the audio output bus.
Auxiliary Send volumes - The attenuation or amplitude of the signal sent to game-defined and user-defined Auxiliary Busses. This property can only be driven by distance.
Low-pass filter - The recursive filter that attenuates high frequencies based on a specified value. The units for the low-pass filter represent the percentage of Low-Pass Filtering that has been applied, where 0 means no low-pass filtering (signal unaffected) and 100 means maximal attenuation.
High-pass filter - The recursive filter that attenuates low frequencies based on a specified value. The units for the high-pass filter represent the percentage of high-pass filtering that has been applied, where 0 means no high-pass filtering (signal unaffected) and 100 means maximal attenuation.
Spread - The amount or percentage of audio that is spread to neighboring speakers allowing for sounds to change over distance from a point source at low values to a completely diffused propagation at high values. A value of 0 means that the channels of an emitting source positioned next to a speaker will only be played in that speaker. A value of 100 means that the channels of the emitting source will be diffused so that they are heard or felt through all speakers. This property can only be driven by distance.
Focus - The percentage value is used to condense the virtual emitters generated by the spread value. For a focus of 0%, the virtual emitters remain unchanged, but at higher values each virtual point is moved closer to the source channel origin. This property can only be driven by distance.
Attenuation property values are relative, which means that the attenuation value is added to the existing property values of the associated object.
To define the Attenuation curves:
Load an object into the Property Editor and switch to the Positioning tab.
Within the Attenuation group box, click the selector to choose or create an Attenuation ShareSet.
You must enable Listener Relative Routing to activate the Attenuation group box.
The Attenuation Editor opens with the property settings of the selected attenuation instance.
In the Max distance text box, specify the distance from the source point where the sound will reach its maximum attenuation.
After the max distance value, the attenuation settings remain constant.
In the Curves group box, select the Distance Volume curve from the list.
The default Distance Volume curve is displayed in the graph view.
The first point on the curve always represents the point source and the last point on the curve always represents the max distance value.
Manipulate the Distance Volume Attenuation curve, by doing any of the following:
Add points along the curve.
Drag points to a new location or type specific values into the X and Y coordinate boxes.
Define the shape of each curve segment.
For specific information on zooming or panning in the graph view, displaying several curves simultaneously, adding, moving, or deleting points, specifying the scaling method, or changing the shape of curve segments, refer to Getting to Know the Graph View.
For the remaining curves, select one of the following options from the Curve list:
None to not use an Attenuation curve for the corresponding property. When “None” is selected, the corresponding property is NOT attenuated and remains at its full strength.
Use Distance Volume to use the same curve as the Distance Volume curve for the corresponding property. This option is only available for the Auxiliary send volumes curve.
Use Project Obstruction to use the same curve as the project Obstruction curve for the corresponding property. This option is only available for the Obstruction and Diffraction curves.
Use Project Occlusion to use the same curve as the project Occlusion curve for the corresponding property. This option is only available for the Occlusion and Transmission curves.
Custom to create a custom Attenuation curve for the corresponding driver property pair.