A distant campfire sounds like it is right beside you. Lower the music and your footsteps go quiet too. Once sound is playing, the next thing to arrange is "where, and how loudly, it is heard".
We build change with distance and per-category volume separately. The former uses Sound Attenuation; the latter uses Sound Class and Sound Mix.
What You'll Learn
- Building a campfire that gets quieter as you walk away, with Sound Attenuation
- Where the position that hears sound (the Listener) actually is
- Raising and lowering music and effects separately with Sound Class and Sound Mix
- How Submix and Audio Volume shape a room's reverb
We first get the campfire fading with distance. Then we add music and effects sliders and confirm both effects in the same level.
- Does the sound have a place it comes from?
- Hands-On 1: quieter as you leave the campfire
- Distance from what, exactly?
- Separate music and effects with Sound Class
- Change the volume multiplier with Sound Mix
- Hands-On 2: build music and effects sliders
- Confirm how it sounds
- Shape reverb with Submix and Audio Volume
- When it does not work
- Bonus: when building it into a game
- Summary
Does the sound have a place it comes from?
Music should sound the same as the camera moves. A campfire should get louder as you approach it. That difference decides your playback method.
2D playback does not use how position in the world affects what you hear. It suits music and button clicks. A stereo clip's left-right spread carries over as is.
Positional playback is for footsteps, campfires, explosions. On top of it you add distance-based volume and direction settings.
| Node | Example use | Return value for later control |
|---|---|---|
| Play Sound 2D | A one-shot button click | None |
| Play Sound at Location | An explosion left at that spot | None |
| Spawn Sound 2D | Music you want to stop later | Audio Component |
| Spawn Sound at Location | A fixed-position sound to control later | Audio Component |
| Spawn Sound Attached | A sound that follows a moving object | Audio Component |
An Audio Component is the part for controlling a playing sound. Store a Spawn node's return value in a variable and you can call Stop on that sound later. The Play Sound nodes have no such return value.
Here we use an Ambient Sound Actor for a fixed-position ambience. It is an Actor for placing and playing a sound, testable without calling playback nodes from Blueprint.
Sound Waves as audio material and Sound Cues that assemble playback are covered in the Sound Wave and Sound Cue article.
Hands-On 1: quieter as you leave the campfire
Use a walkable level such as the Third Person template. Prepare a wide floor and place one Cube as a landmark. You can run the audio experiment without campfire visuals.
Prepare the sound and the placement
- Import a looping campfire sound and name the Sound Wave SW_Fire . A mono clip without separate left and right makes direction easiest to check at first.
- Open SW_Fire and turn on "Looping".
- Set "Virtualization Mode" to Play When Silent .
- Drag SW_Fire into the level and put the created Ambient Sound at the Cube's position.
- Turn on the Ambient Sound's "Auto Activate" and set Volume Multiplier and Pitch Multiplier to 1.0.
Looping repeats the clip when it ends. Auto Activate makes that Actor start playing when Play begins. The two have different roles.
Play When Silent keeps playback running even while inaudible. In this small experiment it makes it easy to return to an audible state after leaving the range or setting the volume to 0. Audio processing continues while silent, so revisit how you use it for large numbers of ambiences later.
Assign an attenuation asset
Attenuation is making a sound quieter with distance. Create a Sound Attenuation asset gathering those settings.
Right-click in the Content Browser, choose "Sound Attenuation" from the audio category, and name it ATT_Ambient .
| Property | Setting |
|---|---|
| Enable Volume Attenuation | On |
| Attenuation Function | Linear |
| Attenuation Shape | Sphere |
| Inner Radius | 300 |
| Falloff Distance | 1500 |
| Enable Spatialization | On |
| Spatialization Method | Panning |
Set the created ATT_Ambient in the placed Ambient Sound's "Attenuation Settings". Leave "Override Attenuation" off and "Allow Spatialization" on.
Override Attenuation is the switch that overrides settings for that placement only. We use the shared asset's values, so leave it off.
Sphere is a spherical range. Inner Radius is from the center to where attenuation begins, and Falloff Distance is the width beyond that. The default unit is cm, so our range works out to:
| Distance to the listening position | Volume multiplier under this Linear setup |
|---|---|
| Up to 3 m | 1.0 |
| 3 m to 18 m | Drops from 1.0 to 0 with distance |
| Beyond 18 m | 0 |
300 + 1500 = 1800 cm, or 18 m. The key is not reading 1500 as "distance from the center".
Save and Play, then walk away from the Cube. Loud up close, quieter as you leave, and audible again as you return means the first stage worked.
Linear is a curve where the multiplier drops by a constant amount per constant distance. We chose it because the result is easy to grasp. Other curves like Natural Sound treat the out-of-range case differently depending on settings. Do not apply "0 at 18 m" to every curve.
Distance from what, exactly?
Volume distance is measured to the Listener, the position of the game's "ears" . It is normally on the camera.
In third person, the camera trails behind even as the character approaches the source. That is why measuring 18 m from the character's feet does not exactly match what you hear. Think in terms of distance in space, height included.
Also, spatialization is the setting that gives direction, so "a sound on the left is heard from the left". Our Panning represents direction through the balance between outputs. It is separate from distance attenuation, so you can use only one of them.
Stereo clips can be spatialized too, but the spread between left and right channels comes into play. Starting with a mono campfire makes approaching, leaving, and turning sideways easiest to hear.
Separate music and effects with Sound Class
Next we make it possible to lower only the music while the campfire stays put. That uses a Sound Class, the categorization that groups sounds by kind . Effects here means sound effects like footsteps and campfires.
Create three Sound Classes from the Content Browser's audio category.
| Asset | Its role here |
|---|---|
| SC_Master | The parent gathering music and effects |
| SC_BGM | Groups the music |
| SC_SE | Groups campfires and footsteps |
Open SC_Master and add SC_BGM and SC_SE to Child Classes. Leave each Class's Volume and Pitch at 1.0 for now.
Sound Classes have their own Volume. Changing the parent's volume affects children, letting you organize overall and per-category volume. We keep the Classes' base values at 1.0 and let Sound Mix carry runtime changes.
Import a looping music track and name it SW_BGM . Configure the two Sound Waves as follows.
| Asset | Sound Class | Looping | Virtualization Mode |
|---|---|---|---|
| SW_BGM | SC_BGM | On | Play When Silent |
| SW_Fire | SC_SE | On | Play When Silent |
New sounds may be assigned the project's default Class. Naming something BGM or SE does not classify it automatically, so check each sound's "Sound Class".
Change the volume multiplier with Sound Mix
A Sound Mix is an asset gathering volume and other adjustments applied to Sound Classes. It can hold a change like "music at 0.5, effects at 1.0".
Create a Sound Mix from the Content Browser's audio category and name it SM_UserAudio . Open it and add these two entries to Sound Class Effects.
| Sound Class Object | Volume Adjuster | Pitch Adjuster | Apply to Children |
|---|---|---|---|
| SC_BGM | 1.0 | 1.0 | On |
| SC_SE | 1.0 | 1.0 | On |
Set the Mix's "Initial Delay" and "Fade in Time" to 0 and "Duration" to -1. That uses it as a setting that never times out after activation.
1.0 leaves it as is and 0 silences it. 0.5 halves the audio signal, which is not the same as "half as loud perceptually".
Push Sound Mix Modifier activates that Mix. We call it once at level start. There is no need to call it every time a slider moves.
Use Set Sound Mix Class Override to change values. Override here means "rewrite that Mix's adjustment for a Class".
Hands-On 2: build music and effects sliders
Now we show a small volume panel in the current level. Music plays, and two sliders rewrite SM_UserAudio. It is a test UI for comparing without stopping the game.
1. Create the Widget
A Widget is a UI element shown on screen. Here we gather two sliders into one volume panel.
Create a Widget Blueprint from "User Interface" in the Content Browser and name it WBP_AudioSettings . Place a Canvas Panel in the Designer, add a Vertical Box as its child, and position it top left. The Canvas Panel is the placement base and the Vertical Box stacks children vertically.
Inside the Vertical Box, place Text "BGM", a Slider, Text "SE", and a Slider, top to bottom. Name the two sliders Slider_BGM and Slider_SE .
| Slider property | Setting |
|---|---|
| Min Value | 0 |
| Max Value | 1 |
| Value | 1 |
| Is Variable | On |
| Is Focusable | Off |
Keep the panel sized to a portion of the screen. Set the Canvas Panel's Visibility to "Not Hit-Testable (Self Only)" so the child sliders remain operable. A full-screen Border is not needed here.
Is Focusable is off so the sliders do not keep receiving keyboard input. That makes it easy to return to the 3D view and walk around after touching the volume.
2. Split the startup work into three
Open the Level Blueprint from the level toolbar. Connect Sequence to Event BeginPlay and use "Add pin" to give it three outputs: Then 0, Then 1, Then 2.
Sequence advances execution through its outputs top to bottom. Here we split it into audio setup, UI display, and input setup. It does not mean "wait until the music finishes".
The diagrams below split the branches from that one Sequence . You do not need three BeginPlays or three Sequences.
3. Then 0: activate the Mix and play the music
From Then 0, wire white exec through Push Sound Mix Modifier → Play Sound 2D .
| Node | Settings |
|---|---|
| Push Sound Mix Modifier | In Sound Mix Modifier = SM_UserAudio |
| Play Sound 2D | Sound = SW_BGM, Volume Multiplier = 1.0, Pitch Multiplier = 1.0 |
We keep it playing in one level for comparison, so Play Sound 2D is fine. To extend to stopping or switching tracks, hold Spawn Sound 2D's return value instead.
4. Then 1: display the panel
From Then 1, wire Create Widget → Add to Viewport .
Set Create Widget's Class to WBP_AudioSettings and connect Get Player Controller (Player Index = 0) 's Return Value to "Owning Player". Connect Create Widget's Return Value to Add to Viewport's Target.
A Player Controller is the Actor handling a player's input. Here we fetch the first player with Index 0 and create the panel as theirs.
Create Widget's return value is the panel you just made. Passing that panel to Add to Viewport displays it.
5. Then 2: enable both mouse and game input
From Then 2, wire Set Input Mode Game And UI → Set Show Mouse Cursor . You can find Set Show Mouse Cursor by dragging from Get Player Controller's Return Value and searching.
Place a Get Player Controller (Player Index = 0) in this branch too and connect its Return Value to Game And UI's Player Controller and Show Mouse Cursor's Target.
| Property | Setting |
|---|---|
| In Widget to Focus | Unconnected |
| In Mouse Lock Mode | Do Not Lock |
| Hide Cursor During Capture | Off |
| Show Mouse Cursor | On |
Game And UI routes input the UI uses to the UI and passes the rest to the game as well. Showing the cursor alone does not change the input mode, so set both.
6. Rewrite Class volume from the sliders
Return to WBP_AudioSettings and select Slider_BGM in the Designer. Press the "+" on "On Value Changed" in Details' Events.
That event fires when the slider's value changes. Connect its white exec output to Set Sound Mix Class Override and the numeric Value to that node's Volume.
| Argument | Setting |
|---|---|
| In Sound Mix Modifier | SM_UserAudio |
| In Sound Class | SC_BGM |
| Volume | The event's Value |
| Pitch | 1.0 |
| Fade in Time | 0.1 |
| Apply to Children | On |
Fade in Time is the number of seconds to move from the current volume to the new one. Here 0.1 seconds keeps it smooth.
Add On Value Changed to Slider_SE and build the same connections. The only difference is In Sound Class = SC_SE . Both specify SM_UserAudio as the Mix.
Compile and save the Blueprints. Both the sliders and the Mix start at 1.0, so both sounds play at their original multipliers at first.
Confirm how it sounds
Play close enough to hear the campfire and operate the sliders. To walk after adjusting, click the 3D view outside the panel first, then use WASD.
| What to try | What you hear |
|---|---|
| Music to 0.5 | Only the music gets quieter; the campfire is unchanged |
| Effects to 0 | The campfire goes silent while the music keeps playing |
| Effects back to 1 | The campfire returns |
| Both at 1, walk away from the fire | The music stays the same; only the campfire fades |
| Approach the campfire again | The campfire gets louder again |
Finally, stop Play and change SW_Fire's Sound Class to SC_BGM once . Play again and the music slider now also lowers the campfire. That confirms "which slider changes what" is decided by the sound's Class assignment. Set it back to SC_SE afterwards.
Shape reverb with Submix and Audio Volume
The hands-on so far adjusts distance and volume. When you want to process several sounds together, or add a room's reverb, use the following.
Submix: a destination that gathers and processes sound
A Submix is a route that gathers several sounds. Place effects there and the gathered audio is processed together.
Create a Sound Submix asset and add effect presets to its "Submix Effect Chain". On the sound side, specify a destination such as "Base Submix" (Sound Submix in some versions).
EQ , for instance, adjusts the strength of low and high frequencies. A Dynamics Processor shapes volume changes, such as taming loud sounds.
Thinking of a Sound Class as gathering categorization and settings, and a Submix as a route that gathers and processes audio, makes them easy to tell apart. Building our music and effects sliders needs no Submix.
Audio Volume: change reverb by place
Reverb is the lingering reflection you hear in a cave. An Audio Volume is an Actor placed in a level marking a region where reverb and other settings change.
To try it, place an Audio Volume covering a cave or room and set the following.
| Property | Example setting |
|---|---|
| Apply Reverb | On |
| Reverb Effect | A Reverb Effect asset you prepared |
| Volume | 0.5 |
| Fade Time | 0.5 seconds |
The sound side has to send to reverb too. To try it with the campfire, turn on ATT_Ambient's "Enable Reverb Send", set Reverb Send Method to Manual, and Manual Reverb Send Level to 0.5. Also check "Send to Master Reverb" on the Sound Class.
That is the setting sending part of the sound to reverb processing. Keep the sound playing while the Listener enters and leaves the region and confirm the reverb switches. 2D sounds have their own reverb send settings, so "2D means no reverb at all" is not true.
When it does not work
| Symptom | Where to check |
|---|---|
| The campfire plays once and stops | SW_Fire's Looping and the Ambient Sound's Auto Activate |
| Nothing changes as you walk away | Whether you are playing in 2D, the ATT_Ambient assignment, Enable Volume Attenuation, Override |
| Distance and loudness disagree | Whether you measure from the Listener rather than the character, whether it is Linear, how you read 300 and 1500 |
| I cannot tell left from right | Enable Spatialization, Allow Spatialization, the actual source and camera positions |
| I cannot touch the sliders | Game And UI, Show Mouse Cursor, the Slider's Is Enabled, UI covering it |
| The sliders change nothing | Whether the Mix was activated, Override's Mix/Class, the Value → Volume connection |
| Music and effects drop together | Whether SW_Fire's Class became SC_BGM, whether you changed the parent Class |
| Nothing returns after going back from 0 | Whether the sound is still playing, Looping and Play When Silent |
| Reverb does not change | The Audio Volume, the Listener's position, the Reverb Effect, the sound's reverb send |
Bonus: when building it into a game
Duck the music only during a menu
To pull sound back only during a menu, separate from user settings, prepare another Mix such as SM_MenuDuck . Set SC_BGM's Volume Adjuster to 0.3, Pitch Adjuster to 1.0, and the Mix's Duration to -1.
Specify the same Mix with Push Sound Mix Modifier when opening the menu and Pop Sound Mix Modifier when closing. Pair Push and Pop and avoid repeating Push while it is open. If you actually pause the game, also check settings that keep audio playing while paused, such as the music's "Is UISound".
Save the setting values
Our sliders return to 1.0 when you restart Play. To keep settings, save the values, read them back at launch, and apply them to both the Mix Override and the sliders' displayed values. That continues into saving and loading and the game settings screen article.
Adjust as sound counts grow
Play When Silent keeps playback processing running while silent. Once you place many ambiences, use it only where needed and revisit it together with Sound Concurrency, which handles simultaneous playback counts.
Also, pushing volume multipliers too high or layering many sounds can distort. Moving where you set volume to a Sound Class does not by itself avoid distortion. Listen to the game's audio together and adjust.
What the player hears and what the AI hears are also separate mechanisms. To notify enemies of noise, use Report Noise Event and the like from the AI Perception article.
Summary
Sound Attenuation shapes how things sound with distance, and Sound Class plus Sound Mix shape per-category volume. Here we confirmed the difference by approaching and leaving the campfire and by moving the music and effects sliders.
As you add sounds, share the attenuation asset among sounds of the same character and classify them into the matching Class. Before adding settings per source, decide "at what distance should this be heard" and "which volume setting should it follow".