🎵 Playing Sounds

Play Sound 2D

Play Sound 2D is the simplest way to play audio. It plays a sound without any 3D positioning—the audio comes through at full volume regardless of where anything is in the world. Perfect for sounds that exist "outside" the game space.

When to Use Play Sound 2D

• UI sounds: Button clicks, menu navigation, notifications
• Music: Background music, victory/defeat stingers
• Voice-over: Narrator, tutorial instructions
• System sounds: Achievement unlocked, save complete
• Non-diegetic audio: Sounds the player hears but characters don't

Using Play Sound 2D in Blueprints

The node is straightforward:

1. In any Blueprint, right-click and search for Play Sound 2D
2. Connect the execution pin to your trigger event
3. Set the Sound input to your Sound Wave, Sound Cue, or MetaSound
4. Optionally adjust Volume Multiplier and Pitch Multiplier

Node Parameters

Figure: Play Sound 2D triggered by a button click event.

Example: UI Button Click Sound

In a Widget Blueprint:

1. Select your Button widget
2. In Details, scroll to Events → click + next to On Clicked
3. In the Event Graph, drag from the On Clicked event
4. Add Play Sound 2D node
5. Set Sound to your UI click sound

Play Sound at Location

Play Sound at Location spawns a 3D sound at a specific world position. The sound is spatialized—volume and panning change based on the listener's position relative to where the sound was spawned. This is ideal for one-shot effects in the game world.

When to Use Play Sound at Location

• Explosions: Sound at the explosion point
• Gunshots: Sound at the weapon's muzzle
• Footsteps: Sound at the character's feet
• Impacts: Bullet hits, object collisions
• Pickups: Item collection sounds
• One-shot environmental: Door slam, switch flip

Using Play Sound at Location

1. Right-click in Blueprint and search for Play Sound at Location
2. Connect the execution pin to your trigger
3. Set the Sound input
4. Provide a Location vector (world space position)
5. Optionally set Rotation for directional sounds

Node Parameters

Figure: Play Sound at Location spawns 3D audio at a world position.

Getting the Location

Common ways to get the location for your sound:

Actor's Location:

Get Actor Location → Play Sound at Location

Component's Location:

Get World Location (Component) → Play Sound at Location

Hit Result Location:

Line Trace → Break Hit Result → Impact Point → Play Sound at Location

Spawn Location:

Spawn Actor → Get Actor Location → Play Sound at Location

Audio Components

Audio Components are the most versatile way to play sounds. Unlike the "fire and forget" nodes, Audio Components give you a persistent reference to control playback—play, stop, pause, adjust volume, and more. They're attached to actors and move with them.

When to Use Audio Components

• Looping sounds: Engine hum, ambient fire, machinery
• Controllable audio: Music that needs to stop/fade
• Moving sound sources: Vehicle engine, flying projectile
• Sounds needing runtime adjustment: Volume/pitch changes
• Persistent environmental audio: Waterfall, torch, air conditioner

Adding an Audio Component

In the Editor (Static):

1. Select an Actor in the level or open an Actor Blueprint
2. In Components panel, click Add
3. Search for and add Audio
4. Configure in Details panel:
   • Set Sound to your audio asset
   • Enable Auto Activate if it should play on spawn
   • Set Attenuation Settings for 3D behavior

In Blueprints (Dynamic):

1. Use Spawn Sound 2D or Spawn Sound at Location
2. These return an Audio Component reference
3. Store the reference to control later

Audio Component Properties

Figure: Audio Component attached to a torch actor for persistent fire sound.

Controlling Audio Components

Audio Components provide functions for runtime control:

Example: Fading Music

// In Level Blueprint or Game Mode
// Store reference to music Audio Component

// To fade out music over 2 seconds:
MusicComponent → Fade Out (Fade Out Duration: 2.0, Fade Volume Level: 0.0)

// To fade in music over 1 second:
MusicComponent → Fade In (Fade In Duration: 1.0, Fade Volume Level: 1.0)

flowchart LR
    A[Spawn Actor] --> B{Auto Activate?}
    B -->|Yes| C[Playing]
    B -->|No| D[Stopped]
    D -->|Play| C
    C -->|Stop| D
    C -->|Set Paused true| E[Paused]
    E -->|Set Paused false| C
    C -->|Fade Out| F[Fading Out]
    F --> D
    D -->|Fade In| G[Fading In]
    G --> C
    
    style C fill:#4CAF50,color:#fff
    style D fill:#666,color:#fff
    style E fill:#FF9800,color:#fff

Figure: Audio Component state transitions.

Choosing the Right Method

With three ways to play sounds, choosing the right one ensures clean code and optimal performance.

Quick Decision Guide

Figure: Decision tree for choosing the right playback method.

Comparison Table

Common Patterns

Pattern 1: UI Feedback

Button OnClicked → Play Sound 2D (UI Click)

Pattern 2: Weapon Fire

Fire Weapon → Get Muzzle Location → Play Sound at Location (Gunshot)

Pattern 3: Character Footsteps

Animation Notify → Get Foot Bone Location → Play Sound at Location (Footstep Cue)

Pattern 4: Vehicle Engine

Vehicle Blueprint:
  - Audio Component (Engine Sound)
  - On Tick: Set Pitch based on RPM

Pattern 5: Background Music

Game Mode Begin Play:
  - Spawn Sound 2D (Music) → Store Reference
  - On Level Complete: Fade Out → Play Victory Sting

Hands-On: Adding Sound Effects to Interactions

Let's wire up audio to gameplay events. You'll add UI sounds, interaction sounds, and environmental audio using all three playback methods. This exercise builds on what you created in Lesson 8.1.

Prerequisites

Before starting, ensure you have:

• Sound assets from Lesson 8.1 (or import new ones)
• A playable level with a character
• Basic knowledge of Widget Blueprints (from Module 7)

Part 1: UI Button Click Sound (Play Sound 2D)

Step 1: Create a Simple UI Widget

1. Right-click in Content Browser → User Interface → Widget Blueprint
2. Name it WBP_TestMenu
3. Open the widget and add a Button to the canvas
4. Add a Text Block inside the button with text "Click Me"
5. Name the button TestButton

Step 2: Add Click Event

1. Select the TestButton
2. In Details panel, scroll to Events
3. Click the + next to On Clicked
4. This creates an event node in the Event Graph

Step 3: Play Sound on Click

1. In the Event Graph, drag from On Clicked (TestButton)
2. Search for and add Play Sound 2D
3. Click the dropdown next to Sound
4. Select your UI click sound (e.g., SW_UI_Click)

Step 4: Display the Widget

1. Open your Player Controller or Level Blueprint
2. On Event BeginPlay:
   • Add Create Widget node
   • Set Class to WBP_TestMenu
   • Add Add to Viewport
3. Add Set Input Mode UI Only and Set Show Mouse Cursor (True)

Step 5: Test

1. Play the level
2. Click the button
3. You should hear the UI click sound

Figure: Simple UI click sound using Play Sound 2D.

Part 2: Item Pickup Sound (Play Sound at Location)

Step 6: Create Pickup Actor

1. Right-click in Content Browser → Blueprint Class → Actor
2. Name it BP_PickupItem
3. Open it and add components:
   • Static Mesh (any visible mesh, like a cube or sphere)
   • Sphere Collision (for overlap detection)
4. Set Sphere Collision radius to 100
5. Set collision to OverlapAllDynamic

Step 7: Add Overlap Event

1. Select the Sphere Collision component
2. In Details, scroll to Events
3. Click + next to On Component Begin Overlap

Step 8: Check for Player and Play Sound

1. From the overlap event, add Cast to your Character class
2. Connect Other Actor to the Cast object pin
3. From Cast success:
   • Add Get Actor Location (Self)
   • Add Play Sound at Location
   • Set Sound to a pickup sound (create one or use existing)
   • Connect location
4. After Play Sound at Location, add Destroy Actor

Step 9: Configure Attenuation

1. The pickup sound needs attenuation to work in 3D
2. Either:
   • Set attenuation on the Sound Wave/Cue asset, OR
   • Create a Sound Attenuation asset and pass it to the node
3. For the node: expand Attenuation Settings and select your attenuation asset

Step 10: Test Pickup

1. Place several BP_PickupItem actors in your level
2. Play the level
3. Walk into a pickup
4. Sound should play at the pickup's location, then it disappears
5. Test from different distances to hear attenuation

Figure: Pickup item plays 3D sound at its location before being destroyed.

Part 3: Looping Torch Sound (Audio Component)

Step 11: Create Torch Actor

1. Right-click in Content Browser → Blueprint Class → Actor
2. Name it BP_Torch
3. Open it and add components:
   • Static Mesh (torch or cylinder shape)
   • Point Light (orange/yellow, flicker optional)
   • Audio component

Step 12: Configure Audio Component

1. Select the Audio component
2. In Details panel, configure:
   • Sound: Your fire/torch loop sound
   • Auto Activate: ✓ (checked)
   • Is UI Sound: ✗ (unchecked — we want 3D)
   • Volume Multiplier: 1.0
   • Attenuation Settings: Select your fire attenuation asset

Step 13: Create Fire Sound Attenuation

If you don't have a fire attenuation asset:

1. Right-click → Sounds → Sound Attenuation
2. Name it SA_Fire
3. Configure:
   • Inner Radius: 50 (close to hear full volume)
   • Falloff Distance: 800 (audible from moderate distance)
   • Attenuation Function: Natural Sound

Step 14: Test the Torch

1. Place BP_Torch actors in your level
2. Play the level
3. Walk toward a torch — fire sound gets louder
4. Walk away — sound fades
5. Walk around it — sound pans left/right

Part 4: Controllable Torch (Toggle Sound)

Step 15: Add Toggle Functionality

1. Open BP_Torch
2. Add a variable: bIsLit (Boolean, default True)
3. Create a custom event: ToggleTorch

Step 16: Implement Toggle Logic

1. In the ToggleTorch event:
   • Add Flip Flop node
   • On A (turning off):
     • Set bIsLit = False
     • Audio Component → Stop
     • Point Light → Set Visibility (False)
   • On B (turning on):
     • Set bIsLit = True
     • Audio Component → Play
     • Point Light → Set Visibility (True)

Step 17: Trigger from Player Interaction

1. Add a Box Collision component to the torch (interaction zone)
2. In your Character Blueprint, add input for "Interact" (E key)
3. On interact:
   • Line trace forward from camera
   • If hit actor is BP_Torch → Call ToggleTorch
4. Or use a simpler overlap approach for this exercise

Figure: Audio Component controlled by toggle event.

Part 5: Bonus - Fade Music on Pause

Step 18: Set Up Background Music

1. In your Player Controller or Game Mode
2. Add a variable: MusicComponent (Audio Component reference)
3. On Begin Play:
   • Spawn Sound 2D with your music track
   • Store the returned Audio Component in MusicComponent

Step 19: Fade on Pause

1. When opening pause menu:
   • MusicComponent → Set Volume Multiplier (0.3) for quick duck
   • Or use Adjust Volume (Target: 0.3, Duration: 0.5) for fade
2. When closing pause menu:
   • MusicComponent → Set Volume Multiplier (1.0)
   • Or Adjust Volume (Target: 1.0, Duration: 0.5)

Troubleshooting

Bonus Challenges

1. Footstep Sounds: Add footstep sounds to your character using Animation Notifies
2. Random Pitch: Use your randomized footstep Sound Cue from Lesson 8.1
3. Weapon Sounds: Add fire and reload sounds to a weapon Blueprint
4. Door Sounds: Play open/close sounds on an interactable door
5. Health Pickup: Play a healing sound when collecting health
6. Low Health Warning: Play a looping heartbeat when health is critical
7. Menu Music: Different music for main menu vs gameplay

Summary

In this lesson, you've learned the three primary methods for playing sounds in Unreal Engine. Choosing the right method for each situation keeps your audio code clean and your game performant.

Key Concepts

Play Sound 2D: The simplest method—plays audio without 3D positioning. Same volume everywhere, no panning or distance attenuation. Use for UI sounds, music, voice-over, and any audio that exists "outside" the game world. Fire-and-forget with no playback control.

Play Sound at Location: Spawns a 3D sound at a specific world position. Volume and panning change based on listener position. Requires mono audio and attenuation settings for proper spatialization. Use for one-shot effects like explosions, gunshots, and impacts. Also fire-and-forget.

Audio Components: The most versatile option—attach to actors for persistent, controllable audio. Supports play, stop, pause, fade, and runtime volume/pitch adjustment. Moves with the owning actor. Use for looping sounds, moving sound sources, and any audio needing runtime control.

Choosing the Right Method: Start with the simplest option that meets your needs. 2D for non-positional audio, Location for one-shots in the world, Components for everything that needs persistence or control.

Method Quick Reference

Audio Component Functions

Common Patterns

UI Feedback: Button Click → Play Sound 2D

Weapon Fire: Get Muzzle Location → Play Sound at Location

Item Pickup: Get Actor Location → Play Sound at Location → Destroy Actor

Environmental Loop: Actor with Audio Component (Auto Activate, Looping)

Vehicle Engine: Audio Component + Tick → Set Pitch based on speed/RPM

Music Control: Spawn Sound 2D → Store Reference → Fade In/Out as needed

Best Practices

• Use the simplest method: Don't use Audio Components when Play Sound 2D would suffice
• Mono for 3D: Always use mono audio files for spatialized sounds
• Configure attenuation: 3D sounds need attenuation settings to fade with distance
• Store references: If you need to control audio later, keep the Audio Component reference
• Clean up: Stop looping sounds when their owning actor is destroyed
• Use Sound Cues: For variation, layer through a Sound Cue rather than multiple nodes
• Test in-game: Audio behavior can differ between editor preview and actual gameplay

Figure: Three methods for different audio playback scenarios.

What's Next?

Now that you can trigger sounds from Blueprints, the next lesson covers Ambient Audio. You'll learn about Ambient Sound actors for easy level audio, Audio Volumes for reverb zones, and strategies for creating immersive environmental soundscapes.

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