Audio System

Description

This skill covers implementing audio in Unity — from basic sound effects to full audio management with AudioMixers, spatial 3D audio, music systems with crossfading, and performance-friendly audio pooling. Good audio is one of the most impactful yet underinvested areas of game development; it provides 50% of the player experience.

When To Use

•Playing sound effects (attacks, footsteps, UI clicks, ambient sounds)
•Setting up a music system with playlists, crossfading, and transitions
•Configuring 3D spatial audio for immersive environments
•Building an AudioMixer with volume groups (Master, Music, SFX, Voice, Ambient)
•Implementing a settings menu for audio volume control
•Optimizing audio memory and runtime performance
•Creating audio pools for frequently played sounds

Prerequisites

•Unity 6 (6000.x)
•Basic understanding of AudioSource and AudioClip
•02 — C# Scripting fundamentals
•07 — ScriptableObjects for data-driven audio

Instructions

1. Audio Architecture Overview

code

Audio System Architecture:
├── AudioManager (Singleton or Service)
│   ├── Music Player (dedicated AudioSource, crossfade support)
│   ├── SFX Pool (pooled AudioSources for one-shots)
│   ├── Ambient Controller (looping environmental audio)
│   └── Voice Controller (dialogue, narration)
│
├── AudioMixer
│   ├── Master Group
│   │   ├── Music Group
│   │   ├── SFX Group
│   │   ├── Voice Group
│   │   └── Ambient Group
│   └── Snapshots (Normal, Paused, Underwater, Combat)
│
└── Audio Data (ScriptableObjects)
    ├── SFX Definitions (clip, volume, pitch, spatial)
    └── Music Playlists (tracks, transition info)

2. AudioMixer Setup

Create: Assets → Create → Audio Mixer → GameAudioMixer

code

GameAudioMixer:
├── Master (exposed param: "MasterVolume")
│   ├── Music (exposed param: "MusicVolume")
│   │   └── Effects: Lowpass Filter (for underwater/paused)
│   ├── SFX (exposed param: "SFXVolume")
│   │   └── Effects: Send to Reverb
│   ├── Voice (exposed param: "VoiceVolume")
│   │   └── Effects: Ducking from Music
│   └── Ambient (exposed param: "AmbientVolume")
│       └── Effects: Reverb Zone
│
├── Snapshots:
│   ├── Normal    — All groups at 0 dB
│   ├── Paused    — Music -10 dB, SFX -80 dB, Lowpass on Music
│   ├── Cutscene  — Music 0 dB, SFX -80 dB, Voice +3 dB
│   └── Underwater — Lowpass on everything, reverb

Expose parameters: Right-click a mixer parameter → "Expose to Script" → name it. This enables runtime volume control.

3. Audio Manager

csharp

using UnityEngine;
using UnityEngine.Audio;

public class AudioManager : MonoBehaviour
{
    public static AudioManager Instance { get; private set; }
    
    [Header("Mixer")]
    [SerializeField] private AudioMixer _mixer;
    
    [Header("Music")]
    [SerializeField] private AudioSource _musicSourceA;
    [SerializeField] private AudioSource _musicSourceB;
    [SerializeField] private float _crossfadeDuration = 2f;
    
    [Header("SFX Pool")]
    [SerializeField] private int _sfxPoolSize = 16;
    [SerializeField] private AudioSource _sfxTemplate;
    
    private AudioSource[] _sfxPool;
    private int _sfxPoolIndex;
    private AudioSource _activeMusicSource;
    private bool _isMusicSourceA = true;
    
    private void Awake()
    {
        if (Instance != null && Instance != this)
        {
            Destroy(gameObject);
            return;
        }
        Instance = this;
        DontDestroyOnLoad(gameObject);
        
        InitializeSFXPool();
        _activeMusicSource = _musicSourceA;
    }
    
    // --- SFX ---
    
    private void InitializeSFXPool()
    {
        _sfxPool = new AudioSource[_sfxPoolSize];
        for (int i = 0; i < _sfxPoolSize; i++)
        {
            var go = new GameObject($"SFX_Source_{i}");
            go.transform.SetParent(transform);
            _sfxPool[i] = go.AddComponent<AudioSource>();
            _sfxPool[i].outputAudioMixerGroup = _sfxTemplate.outputAudioMixerGroup;
            _sfxPool[i].playOnAwake = false;
        }
    }
    
    /// <summary>
    /// Play a one-shot SFX (2D — UI clicks, pickups, non-spatial).
    /// </summary>
    public void PlaySFX(AudioClip clip, float volume = 1f, float pitchVariance = 0f)
    {
        if (clip == null) return;
        
        AudioSource source = GetNextSFXSource();
        source.spatialBlend = 0f; // 2D
        source.clip = clip;
        source.volume = volume;
        source.pitch = 1f + Random.Range(-pitchVariance, pitchVariance);
        source.Play();
    }
    
    /// <summary>
    /// Play a SFX at a world position (3D spatial audio).
    /// </summary>
    public void PlaySFXAtPoint(AudioClip clip, Vector3 position, float volume = 1f, 
        float pitchVariance = 0.05f)
    {
        if (clip == null) return;
        
        AudioSource source = GetNextSFXSource();
        source.transform.position = position;
        source.spatialBlend = 1f; // Full 3D
        source.clip = clip;
        source.volume = volume;
        source.pitch = 1f + Random.Range(-pitchVariance, pitchVariance);
        source.Play();
    }
    
    /// <summary>
    /// Play a random clip from an array (great for footsteps, hits).
    /// </summary>
    public void PlayRandomSFX(AudioClip[] clips, Vector3 position, float volume = 1f)
    {
        if (clips == null || clips.Length == 0) return;
        PlaySFXAtPoint(clips[Random.Range(0, clips.Length)], position, volume);
    }
    
    private AudioSource GetNextSFXSource()
    {
        var source = _sfxPool[_sfxPoolIndex];
        _sfxPoolIndex = (_sfxPoolIndex + 1) % _sfxPoolSize;
        return source;
    }
    
    // --- Music ---
    
    /// <summary>
    /// Play music with crossfade from current track.
    /// </summary>
    public void PlayMusic(AudioClip clip, bool loop = true)
    {
        if (clip == null) return;
        
        var newSource = _isMusicSourceA ? _musicSourceB : _musicSourceA;
        newSource.clip = clip;
        newSource.loop = loop;
        newSource.Play();
        
        StartCoroutine(CrossfadeMusic(_activeMusicSource, newSource));
        
        _activeMusicSource = newSource;
        _isMusicSourceA = !_isMusicSourceA;
    }
    
    public void StopMusic()
    {
        StartCoroutine(FadeOut(_activeMusicSource, _crossfadeDuration));
    }
    
    private System.Collections.IEnumerator CrossfadeMusic(AudioSource from, AudioSource to)
    {
        float elapsed = 0f;
        float fromStartVol = from.volume;
        
        to.volume = 0f;
        
        while (elapsed < _crossfadeDuration)
        {
            elapsed += Time.unscaledDeltaTime;
            float t = elapsed / _crossfadeDuration;
            
            from.volume = Mathf.Lerp(fromStartVol, 0f, t);
            to.volume = Mathf.Lerp(0f, 1f, t);
            
            yield return null;
        }
        
        from.Stop();
        from.volume = fromStartVol;
        to.volume = 1f;
    }
    
    private System.Collections.IEnumerator FadeOut(AudioSource source, float duration)
    {
        float startVol = source.volume;
        float elapsed = 0f;
        
        while (elapsed < duration)
        {
            elapsed += Time.unscaledDeltaTime;
            source.volume = Mathf.Lerp(startVol, 0f, elapsed / duration);
            yield return null;
        }
        
        source.Stop();
        source.volume = startVol;
    }
    
    // --- Mixer Volume Control ---
    
    /// <summary>
    /// Set volume on a mixer group. Value is 0-1 (linear), converted to dB.
    /// </summary>
    public void SetVolume(string exposedParam, float linearVolume)
    {
        // Convert linear (0-1) to logarithmic dB (-80 to 0)
        float dB = linearVolume > 0.001f 
            ? Mathf.Log10(linearVolume) * 20f 
            : -80f;
        _mixer.SetFloat(exposedParam, dB);
    }
    
    public float GetVolume(string exposedParam)
    {
        _mixer.GetFloat(exposedParam, out float dB);
        return Mathf.Pow(10f, dB / 20f); // Convert dB back to linear
    }
    
    // --- Snapshots ---
    
    public void TransitionToSnapshot(string snapshotName, float duration = 1f)
    {
        var snapshot = _mixer.FindSnapshot(snapshotName);
        snapshot?.TransitionTo(duration);
    }
}

4. ScriptableObject Audio Definitions

Data-driven audio for easy designer tuning:

csharp

using UnityEngine;

[CreateAssetMenu(fileName = "New SFX", menuName = "Audio/SFX Definition")]
public class SFXDefinition : ScriptableObject
{
    [Header("Clips")]
    [SerializeField] private AudioClip[] _clips;
    
    [Header("Playback")]
    [Range(0f, 1f)] public float volume = 1f;
    [Range(0f, 0.3f)] public float pitchVariance = 0.05f;
    [Range(0f, 1f)] public float spatialBlend = 1f;
    
    [Header("Cooldown")]
    [Tooltip("Minimum seconds between plays (prevents sound stacking)")]
    public float cooldown = 0.05f;
    
    [System.NonSerialized] private float _lastPlayTime;
    
    public AudioClip GetRandomClip()
    {
        if (_clips == null || _clips.Length == 0) return null;
        return _clips[Random.Range(0, _clips.Length)];
    }
    
    public bool CanPlay()
    {
        if (Time.time - _lastPlayTime < cooldown) return false;
        _lastPlayTime = Time.time;
        return true;
    }
    
    public void Play(Vector3 position)
    {
        if (!CanPlay()) return;
        AudioManager.Instance.PlaySFXAtPoint(GetRandomClip(), position, volume, pitchVariance);
    }
    
    public void Play2D()
    {
        if (!CanPlay()) return;
        AudioManager.Instance.PlaySFX(GetRandomClip(), volume, pitchVariance);
    }
}

Usage:

csharp

public class Weapon : MonoBehaviour
{
    [SerializeField] private SFXDefinition _swingSound;
    [SerializeField] private SFXDefinition _hitSound;
    
    public void OnSwing() => _swingSound.Play(transform.position);
    public void OnHit(Vector3 hitPoint) => _hitSound.Play(hitPoint);
}

5. Music Playlist System

csharp

[CreateAssetMenu(fileName = "New Playlist", menuName = "Audio/Music Playlist")]
public class MusicPlaylist : ScriptableObject
{
    public AudioClip[] tracks;
    public bool shuffle = false;
    public float trackGap = 1f; // Seconds between tracks
    
    [System.NonSerialized] private int _currentIndex;
    [System.NonSerialized] private int[] _shuffledOrder;
    
    public AudioClip GetNextTrack()
    {
        if (tracks == null || tracks.Length == 0) return null;
        
        if (shuffle)
        {
            if (_shuffledOrder == null || _shuffledOrder.Length != tracks.Length)
                ReShuffle();
            
            var clip = tracks[_shuffledOrder[_currentIndex]];
            _currentIndex = (_currentIndex + 1) % tracks.Length;
            
            if (_currentIndex == 0) ReShuffle();
            return clip;
        }
        
        var track = tracks[_currentIndex];
        _currentIndex = (_currentIndex + 1) % tracks.Length;
        return track;
    }
    
    private void ReShuffle()
    {
        _shuffledOrder = new int[tracks.Length];
        for (int i = 0; i < tracks.Length; i++) _shuffledOrder[i] = i;
        
        // Fisher-Yates shuffle
        for (int i = tracks.Length - 1; i > 0; i--)
        {
            int j = Random.Range(0, i + 1);
            (_shuffledOrder[i], _shuffledOrder[j]) = (_shuffledOrder[j], _shuffledOrder[i]);
        }
    }
}

6. 3D Spatial Audio Configuration

Configure AudioSource for realistic 3D audio:

code

AudioSource (3D Spatial Settings):
  Spatial Blend: 1.0 (full 3D)
  Doppler Level: 0.5 (subtle doppler for moving sources)
  Min Distance: 1    (full volume within this radius)
  Max Distance: 30   (inaudible beyond this)
  Rolloff Mode: Logarithmic (realistic) or Custom (game-tuned)
  Spread: 0-360 (stereo width — 0 for point, 360 for ambient)
  
Reverb Zone Mix: 1.0 (respect reverb zones)

Audio Reverb Zones

Place AudioReverbZone components in your environment:

Zone	Preset	Where
Cave	Cave preset	Underground areas
Hall	Hall preset	Large indoor rooms
Forest	Forest preset	Outdoor wooded areas
Bathroom	Bathroom preset	Small tiled rooms
None	Off	Open outdoor areas

7. Footstep System

csharp

using UnityEngine;

public class FootstepSystem : MonoBehaviour
{
    [System.Serializable]
    public class SurfaceAudio
    {
        public PhysicsMaterial surfaceMaterial;
        public SFXDefinition footstepSound;
    }
    
    [SerializeField] private SurfaceAudio[] _surfaces;
    [SerializeField] private SFXDefinition _defaultFootstep;
    [SerializeField] private float _rayDistance = 1.2f;
    [SerializeField] private LayerMask _groundMask;
    
    /// <summary>
    /// Called from Animation Event on walk/run clips.
    /// </summary>
    public void OnFootstep()
    {
        if (Physics.Raycast(transform.position + Vector3.up * 0.1f, Vector3.down, 
            out RaycastHit hit, _rayDistance, _groundMask))
        {
            var material = hit.collider.sharedMaterial;
            SFXDefinition sound = _defaultFootstep;
            
            foreach (var surface in _surfaces)
            {
                if (surface.surfaceMaterial == material)
                {
                    sound = surface.footstepSound;
                    break;
                }
            }
            
            sound.Play(hit.point);
        }
    }
}

8. Volume Settings UI

csharp

using UnityEngine;
using UnityEngine.UI;

public class AudioSettingsUI : MonoBehaviour
{
    [SerializeField] private Slider _masterSlider;
    [SerializeField] private Slider _musicSlider;
    [SerializeField] private Slider _sfxSlider;
    [SerializeField] private Slider _voiceSlider;
    
    private void Start()
    {
        // Load saved settings
        _masterSlider.value = PlayerPrefs.GetFloat("MasterVolume", 1f);
        _musicSlider.value = PlayerPrefs.GetFloat("MusicVolume", 0.8f);
        _sfxSlider.value = PlayerPrefs.GetFloat("SFXVolume", 1f);
        _voiceSlider.value = PlayerPrefs.GetFloat("VoiceVolume", 1f);
        
        // Apply
        ApplyVolumes();
        
        // Listen for changes
        _masterSlider.onValueChanged.AddListener(_ => ApplyVolumes());
        _musicSlider.onValueChanged.AddListener(_ => ApplyVolumes());
        _sfxSlider.onValueChanged.AddListener(_ => ApplyVolumes());
        _voiceSlider.onValueChanged.AddListener(_ => ApplyVolumes());
    }
    
    private void ApplyVolumes()
    {
        AudioManager.Instance.SetVolume("MasterVolume", _masterSlider.value);
        AudioManager.Instance.SetVolume("MusicVolume", _musicSlider.value);
        AudioManager.Instance.SetVolume("SFXVolume", _sfxSlider.value);
        AudioManager.Instance.SetVolume("VoiceVolume", _voiceSlider.value);
    }
    
    public void SaveSettings()
    {
        PlayerPrefs.SetFloat("MasterVolume", _masterSlider.value);
        PlayerPrefs.SetFloat("MusicVolume", _musicSlider.value);
        PlayerPrefs.SetFloat("SFXVolume", _sfxSlider.value);
        PlayerPrefs.SetFloat("VoiceVolume", _voiceSlider.value);
        PlayerPrefs.Save();
    }
}

9. Audio Import Settings

Audio Type	Load Type	Compression	Sample Rate
Short SFX (< 1s)	Decompress On Load	PCM or ADPCM	Original
Medium SFX (1-5s)	Compressed In Memory	Vorbis (70%)	22050 Hz
Music (> 5s)	Streaming	Vorbis (50-70%)	44100 Hz
Ambient loops	Compressed In Memory	Vorbis (50%)	22050 Hz
Voice/Dialogue	Streaming	Vorbis (70%)	22050 Hz

Key rules:

•Always set mono for 3D spatial SFX (stereo is wasted for spatialized audio).

•Use streaming for music and long audio to reduce memory.

•Force mono on mobile for all SFX to halve memory usage.

Best Practices

•Use an AudioMixer — always route audio through mixer groups for global volume control.
•Convert linear to dB for mixer volume: dB = Mathf.Log10(linear) * 20f. Never set raw 0–1 on mixer params.
•Pool AudioSources for SFX — AudioSource.PlayClipAtPoint creates and destroys a GameObject each call.
•Add pitch variance (±5%) on repeated SFX — prevents machine-gun repetition on footsteps, hits, shots.
•Use multiple clips per sound — cycle or randomize to avoid listener fatigue.
•Set cooldowns on frequently triggered sounds — prevents audio stacking and clipping.
•Use Time.unscaledDeltaTime for music crossfades — music should continue during pause.
•Mark 3D SFX as mono — stereo 3D audio wastes memory and can cause spatial confusion.
•Use Streaming for music — keeps memory usage low for long tracks.
•Always use AudioMixer Snapshots for state changes (pause, underwater) instead of manual parameter tweaking.

Common Pitfalls

Pitfall	Why It Hurts	Fix
Using `AudioSource.PlayClipAtPoint`	Creates/destroys GameObjects (GC pressure)	Use an AudioSource pool
Setting mixer volume with linear 0–1	Volume sounds wrong (not perceptually linear)	Convert to dB: `Log10(v) * 20`
Stereo clips for 3D audio	Doubled memory, poor spatialization	Import as mono for 3D SFX
"Decompress On Load" for music	Huge memory usage for long tracks	Use Streaming for music
No pitch variation on repeated SFX	Sounds robotic and repetitive	Add ±5% random pitch variance
Playing too many sounds simultaneously	Audio clipping, muddy mix	Set a maximum concurrent sound count per category
AudioMixer volume at -80 dB instead of 0 at start	Silent game until settings loaded	Load and apply saved settings in `Start()`
Not using mixer groups	Can't control volume by category	Route every AudioSource through a mixer group

10 Audio System

Audio System

Description

When To Use

Prerequisites

Instructions

1. Audio Architecture Overview

2. AudioMixer Setup

3. Audio Manager

4. ScriptableObject Audio Definitions

5. Music Playlist System

6. 3D Spatial Audio Configuration

Audio Reverb Zones

7. Footstep System

8. Volume Settings UI

9. Audio Import Settings

Best Practices

Common Pitfalls

Reference