Unreal Engine streamlines the process by which you can produce or modify ambient sounds through the use of the Ambient Sound Actor. When a Sound Wave or Sound Cue asset is placed in a level, an Ambient Sound Actor with that sound asset is created. The Ambient Sound Actor has several properties which are covered on this page that will allow you to modify how players receive the sound.
For more information on importing files as Sound Waves or modifying files through Sound Cues, refer to their respective pages for additional documentation.
Ambient Sound Actor
The Ambient Sound Actor can be used for many purposes such as ambient looping sounds as well as non-looping sounds. Generally, the Ambient Sound Actor conforms to the real world where the closer you are to a sound, the louder it will appear. By comparison, a sound that is normally loud, may appear soft if it is further away.
If the Ambient Sound Actor is set to Auto Activate, it will immediately begin to play once it is created (at the beginning of play or on spawn), even if the player is not in a position to hear it.
The sound asset the Ambient Sound Actor points to will only play once per trigger unless specified as Looping in the Sound Wave or defined as part of a Sound Cue asset.
You can add an Ambient Sound Actor to your level in several ways:
- Select the Ambient Sound Actor from the Place Actors panel in the All Classes tab and drag it into your level as seen below.
- Right-click in your level and select Place Actor from the context menu.
- Open the Actor menu in the Menu bar and select Place Actor.
- Drag a Sound Wave or Sound Cue from the Content Browser into your level.
Sound Properties
An Ambient Sound Actor has no function without an associated sound asset.
You can assign a sound asset from the Details panel by selecting an asset from the Sound setting's drop-down menu or by highlighting a sound asset in the Content Browser and clicking the 
button.
Click image for full size.
Once a Sound Cue asset has been assigned as the associated sound, the Edit option will become available so that you can open the Sound Cue asset up for editing inside the Sound Cue Editor. Optionally, instead of assigning a sound asset, you can select the New option which will create a new Sound Cue asset and will open it in the Sound Cue Editor for editing.
The Play and Stop options allow you to preview the assigned sound inside the editor and will play and stop playing the sound respectively.
Click image for full size.
Additional options inside the Sound section of the Details panel are defined below.
| Property | Description |
|---|---|
| Sound | Points to a Sound Wave or Sound Cue asset. |
| Volume Multiplier | Modifier applied to set the overall Volume of the sound. |
| Pitch Multiplier | Modifier applied to set the overall Pitch of the sound. |
| Is UI Sound | Whether or not the sound asset plays when the game is paused. |
| Low Pass Filter Frequency | Enable to set the frequency (in Hz) of the low pass Filter. A frequency of 0.0 is the device sample rate and will bypass the filter. |
| Priority | Enable to override the priority of selected sound with the value provided. |
| Play Multiple Instances | If true, the Audio Component plays multiple sound instances at once. |
| Source Effect Chain | Determines a chain of source effects to apply to the sounds playing on the Audio Component. |
Attenuation Properties
Attenuation is the ability of a sound to decrease in volume as the player moves away from it. It works using two radii: MinRadius and MaxRadius. As you move from the sound's origin through the MinRadius, the volume of the sound is at 100%. As you move within the space between the MinRadius and the MaxRadius, the volume level is adjusted based on the Distance Algorithm. Outside of the MaxRadius, the volume of the sound is at 0%.
It is advisable to use Sound Attenuation objects whenever possible, if for no other reason than to give broad control over the settings for many Actors.
For additional information on Attenuation, please refer to the Attenuation Overview page.
The options under the Attenuation section that can be modified inside the Details panel are defined below:
| Property | Description |
|---|---|
| Allow Spatialization | Enables or disables spatialization of the audio component. |
| Override Attenuation | Uses the asset's Attenuation settings or the Attenuation Override's settings. |
| Attenuation Settings | Points to and uses the settings assigned inside a SoundAttenuation asset. |
When Override Attenuation is checked, the ability to modify settings on the following sections becomes available:
| Section | Description |
|---|---|
| Attenuation (Volume) | Properties in this section define how the sound's volume will attenuate as the listener moves away from it. |
| Attenuation (Spatialization) | Properties in this section define how the sound will spatialize in the game world. |
| Attenuation (Occlusion) | Properties in this section control real-time occlusion tracing. |
| Attenuation (Submix) | Properties in this section control sending sound sources to a submix. |
| Attenuation (Reverb) | Properties in this section define the relationship between the sound's distance from the listener and the amount of reverb that is applied to the sound. |
| Attenuation (Focus) | Properties in this section control some additional processing that you can use to the 'focus behavior' of sounds. |
| Attenuation (Priority) | Properties in this section control attenuation of sound priority based on distance. |
| Attenuation (Air Absorption) | Properties in this section define the behavior of the algorithm that attempts to model the effect air absorption has on the sound. |
Modulation Properties
The Modulation settings define what settings to use for Volume, Pitch, Highpass and Lowpass modulation. There are three options available:
- Disable: Disables modulation routing.
- Inherit: The Audio Component inherits modulation settings from its parent Sound.
- Override: Ignores inherited settings and allows you to set the base value, enable or disable modulation and set the modulation source for each parameter.
For additional information on Modulation, please refer to the Overview of Audio Modulation in Unreal Engine page.
Adding Audio Components To Blueprints
Inside a Blueprint, in the Component panel, select the Add Component button and select the Audio component.
The Audio component can be referenced through Blueprints and many of its settings can be altered by using different types of functions.
The Audio component does have a unique event which can be used. This OnAudioFinished event allows you to fire off events when the audio is finished playing or is stopped prematurely with a Stop function.
Audio Volumes
For an added level of control, you can include Audio Volumes in conjunction with Ambient Sound Actors. For more information on how to use an Audio Volume, refer to the Audio Volumes page.
Making changes to an Audio Volume will not work in real time inside the editor. You will need to rebuild the geometry of the level that contains the edited volume in order for your changes to take effect.