/audio-system

name: audio-system
description: Use when implementing audio — audio buses, AudioStreamPlayer, spatial audio, music management, SFX pooling, and dynamic mixing

Audio System in Godot 4.3+

All examples target Godot 4.3+ with no deprecated APIs. GDScript is shown first, then C#.

> **Related skills:** **event-bus** for decoupled audio triggers, **save-load** for persisting audio settings, **resource-pattern** for audio data containers.

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1. Core Concepts

Audio Node Types

| Node | Dimensions | Use For | |------------------------|------------|-----------------------------------------------| | `AudioStreamPlayer` | Non-positional | Music, UI sounds, global SFX | | `AudioStreamPlayer2D` | 2D positional | Footsteps, gunfire, environmental sounds | | `AudioStreamPlayer3D` | 3D positional | Same as 2D but in 3D space |

Audio Bus Architecture

Godot routes all audio through **buses** (like a mixing console).

Master (always exists)
├── Music          → volume, effects for background music
├── SFX            → volume, effects for sound effects
│   ├── Footsteps  → sub-bus for fine-tuning
│   └── Weapons    → sub-bus for fine-tuning
└── UI             → volume for menu sounds

**Setup:** Bottom panel → Audio tab → Add buses, set names, route outputs.

Every AudioStreamPlayer has a `bus` property — set it to the target bus name (e.g., `"SFX"`, `"Music"`).

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2. Basic Audio Playback

GDScript

extends Node2D

@onready var sfx_player: AudioStreamPlayer2D = $AudioStreamPlayer2D
@onready var music_player: AudioStreamPlayer = $MusicPlayer

func _ready() -> void:
    # Play background music (looping is set on the AudioStream resource)
    music_player.play()

func play_jump_sound() -> void:
    sfx_player.stream = preload("res://audio/sfx/jump.wav")
    sfx_player.play()

C#

using Godot;

public partial class AudioExample : Node2D
{
    private AudioStreamPlayer2D _sfxPlayer;
    private AudioStreamPlayer _musicPlayer;

    public override void _Ready()
    {
        _sfxPlayer = GetNode<AudioStreamPlayer2D>("AudioStreamPlayer2D");
        _musicPlayer = GetNode<AudioStreamPlayer>("MusicPlayer");
        _musicPlayer.Play();
    }

    public void PlayJumpSound()
    {
        _sfxPlayer.Stream = GD.Load<AudioStream>("res://audio/sfx/jump.wav");
        _sfxPlayer.Play();
    }
}

Looping Audio

Looping is configured on the **AudioStream resource**, not the player node:

• **WAV:** Import tab → Loop Mode → Forward (or Ping-Pong)
• **OGG:** Import tab → Loop → On, set Loop Offset
• **MP3:** Import tab → Loop → On

> Always use OGG Vorbis for music (smaller files, good quality). Use WAV for short SFX (PCM or QOA, cheap to decode). Avoid MP3 for SFX — depending on the encoder it can start with padding silence.

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3. Audio Bus Management

Setting Volume from Code

Godot uses **decibels (dB)** for volume. Linear-to-dB conversion is required for sliders.

GDScript

# Get bus index by name
var bus_index: int = AudioServer.get_bus_index("SFX")

# Set volume in dB directly
AudioServer.set_bus_volume_db(bus_index, -6.0)  # -6 dB ≈ half amplitude (db_to_linear(-6.0) ≈ 0.5)

# Convert linear (0.0–1.0) to dB — use for UI sliders
func set_bus_volume_linear(bus_name: String, linear: float) -> void:
    var index := AudioServer.get_bus_index(bus_name)
    AudioServer.set_bus_volume_db(index, linear_to_db(linear))

# Mute / unmute a bus
AudioServer.set_bus_mute(bus_index, true)

# Read current volume as linear (for displaying on a slider)
func get_bus_volume_linear(bus_name: String) -> float:
    var index := AudioServer.get_bus_index(bus_name)
    return db_to_linear(AudioServer.get_bus_volume_db(index))

C#

int busIndex = AudioServer.GetBusIndex("SFX");

// Set volume in dB
AudioServer.SetBusVolumeDb(busIndex, -6.0f);

// Linear to dB conversion for UI sliders
public void SetBusVolumeLinear(string busName, float linear)
{
    int index = AudioServer.GetBusIndex(busName);
    AudioServer.SetBusVolumeDb(index, Mathf.LinearToDb(linear));
}

// Mute / unmute
AudioServer.SetBusMute(busIndex, true);

// Read current volume as linear
public float GetBusVolumeLinear(string busName)
{
    int index = AudioServer.GetBusIndex(busName);
    return Mathf.DbToLinear(AudioServer.GetBusVolumeDb(index));
}

Audio Bus Effects

Add effects to buses in the Audio panel (bottom dock). Common effects:

| Effect | Use For | |-----------------|---------------------------------------------| | `Reverb` | Cave, cathedral, bathroom ambience | | `Delay` | Echo effects | | `Compressor` | Normalize loud/quiet sounds (master bus) | | `HardLimiter` | Prevent clipping on master bus (`Limiter` is deprecated) | | `LowPassFilter` | Muffled sounds (underwater, behind walls) | | `HighPassFilter` | Thin/tinny sound (radio, phone) | | `Chorus` | Thicken sounds | | `Distortion` | Gritty/overdrive effects | | `EQ` | Fine-tune frequency bands |

Dynamic Effect Toggle

# Enable/disable an effect on a bus at runtime
var bus_index := AudioServer.get_bus_index("SFX")
var effect_index := 0  # First effect on the bus
AudioServer.set_bus_effect_enabled(bus_index, effect_index, true)

# Apply low-pass filter for "underwater" feel
func set_underwater(enabled: bool) -> void:
    var index := AudioServer.get_bus_index("SFX")
    # Assumes a LowPassFilter is the first effect on the SFX bus
    AudioServer.set_bus_effect_enabled(index, 0, enabled)

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4. Spatial Audio (2D & 3D)

AudioStreamPlayer2D

Automatically adjusts volume and panning based on distance to the current `AudioListener2D` (or the centre of th