audio-system

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 (no decoding latency). Avoid MP3 for SFX — it adds silence at the start.

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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 = ~50% perceived volume

# 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)
Limiter	Prevent clipping on master bus
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 nearest AudioListener2D (or the Camera2D if no listener exists).

Enemy (CharacterBody2D)
├── Sprite2D
└── AudioStreamPlayer2D   ← positioned at enemy's location
    bus = "SFX"
    max_distance = 1000.0
    attenuation = 1.0

Key properties:

Property	Description	Default
max_distance	Beyond this distance, sound is silent	2000.0
attenuation	Volume falloff curve (1.0 = linear, higher = sharper)	1.0
max_polyphony	Max simultaneous instances of this player	1
panning_strength	How much the sound pans left/right	1.0

AudioStreamPlayer3D

Same concept but in 3D. Works with AudioListener3D (or the Camera3D).

Key additional properties:

Property	Description
unit_size	Distance at which volume is 0 dB
max_db	Maximum volume cap
attenuation_model	Inverse, InverseSquare, Logarithmic, Disabled
doppler_tracking	Enable Doppler effect for moving sources

AudioListener

# Make a specific camera the audio listener
# 2D: add AudioListener2D as child of Camera2D, call make_current()
# 3D: add AudioListener3D as child of Camera3D, call make_current()

# By default, the current Camera2D/3D acts as the listener.
# Only add an explicit AudioListener if you need a different listening position.

// 2D spatial player
public partial class Footsteps : AudioStreamPlayer2D
{
    public override void _Ready()
    {
        Bus = "SFX";
        MaxDistance = 1000.0f;     // Pixels at which volume reaches zero
        Attenuation = 1.0f;         // Linear falloff (higher = sharper)
        MaxPolyphony = 4;           // Allow overlapping footstep sounds
    }

    public void PlayStep() => Play();
}

// 3D spatial player
public partial class EngineHum : AudioStreamPlayer3D
{
    public override void _Ready()
    {
        Bus = "SFX";
        UnitSize = 4.0f;            // Meters at which volume is 0 dB
        MaxDistance = 50.0f;
        AttenuationModel = AttenuationModelEnum.InverseDistance;
    }
}

// Custom listener — overrides the default Camera2D / Camera3D listener.
public partial class FollowCamListener : AudioListener3D
{
    public override void _Ready() => MakeCurrent();
}

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5. Music Manager (Autoload)

Crossfade between background tracks via a singleton autoload that manages two AudioStreamPlayer nodes and tweens their volume_db. Wire a Music audio bus so the settings menu can adjust music separately.

See references/music-manager.md for the full GDScript and C# autoload (crossfade, push/pop stack, current-track query).

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6. SFX Pool

Pre-instantiate a fixed pool of AudioStreamPlayer nodes; play_sfx(stream) finds the next free player and plays. Avoids per-shot instancing churn for high-volume effects (gunshots, footsteps, hits).

See references/sfx-pooling.md for the GDScript + C# pooled player and a 2D positional variant (pool of AudioStreamPlayer2D nodes that follow a target).

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7. Audio Settings Integration

Wire HSliders in the settings menu to bus volumes via AudioServer.set_bus_volume_db(bus_idx, linear_to_db(value)). Persist with ConfigFile. Use the linear_to_db / db_to_linear helpers — never log-base by hand.

See references/audio-settings.md for the full settings menu wiring with persistence (GDScript + C#).

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8. Interactive & Adaptive Music (Godot 4.3+)

Three stream types for adaptive music: AudioStreamPlaylist (sequenced or shuffled tracks), AudioStreamSynchronized (multiple stems played in sync — vertical layering for combat intensity), AudioStreamInteractive (clip transitions on triggers — state-driven music). Godot 4.4+ adds AudioStreamWAV.load_from_file() for runtime WAV loading.

See references/interactive-music.md for the stream-type comparison, GDScript recipes, and the 4.4+ runtime-load example.

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9. Audio Import Best Practices

Format	Use For	File Size	Decode Latency	Loop Support
WAV	Short SFX	Large	None (PCM)	Via import
OGG	Music, long SFX	Small	Minimal	Via import
MP3	Music (fallback)	Small	Has padding	Via import

Import Settings

In the Import dock (select an audio file):

• Loop: Enable for music and ambient loops
• BPM / Beat Count / Bar Beats: Set for rhythm-synced games
• Force Mono: Enable for 3D positional audio (stereo doesn't spatialize well)

Tip: Keep SFX as 16-bit WAV at 44.1kHz. Godot stores WAV uncompressed in PCK, so they play instantly with zero decode overhead. For music, OGG Vorbis at quality 6–8 is a good balance.

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11. Common Pitfalls

Symptom	Cause	Fix
Sound doesn't play	Player not in the scene tree	Ensure the AudioStreamPlayer is add_child()'d before play()
Sound plays but no audio heard	Wrong bus name or bus is muted	Check bus property matches a bus name exactly (case-sensitive)
Music restarts on scene change	Player is part of the scene, not an autoload	Move music player to an autoload (MusicManager)
Positional audio has no panning	No AudioListener or Camera in the scene	Add an AudioListener2D/3D or ensure a Camera is current
Sound clicks or pops	Audio file has no fade-in/fade-out	Add a tiny fade (2–5ms) at start/end of WAV in audio editor
Too many sounds playing at once	No polyphony limit	Set max_polyphony on players or use an SFX pool
Volume slider feels non-linear	Using dB directly instead of linear conversion	Use linear_to_db() / db_to_linear() for slider values
3D audio sounds mono/flat	Stereo source file	Import as mono (Force Mono in Import tab) for 3D spatialization
MP3 has silence at start	MP3 format adds encoder padding	Use WAV for timing-critical SFX, OGG for music

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12. Implementation Checklist

• Audio buses are set up: Master, Music, SFX (minimum)
• All AudioStreamPlayer nodes have the correct bus property assigned
• Music uses OGG Vorbis format; short SFX uses WAV
• Music player is in an autoload (survives scene changes)
• Music crossfading is implemented for smooth transitions
• SFX pool is used instead of creating new AudioStreamPlayer nodes dynamically
• Volume sliders use linear_to_db() / db_to_linear() conversion
• Near-zero slider values mute the bus (avoid linear_to_db(0.0) = -inf)
• 3D audio sources use mono audio files for proper spatialization
• Audio settings are saved and restored on game launch (ConfigFile or similar)
• Looping is configured on the AudioStream resource, not in code
• Interactive/adaptive music uses AudioStreamPlaylist, AudioStreamSynchronized, or AudioStreamInteractive (Godot 4.3+) instead of manual track-switching code