Audio Listener

The Audio Listener acts as a microphone-like device. It receives input from any given Audio Source in the scene and plays sounds through the computer speakers. For most applications it makes the most sense to attach the listener to the Main Camera. If an audio listener is within the boundaries of a Reverb Zone reverberation is applied to all audible sounds in the scene. (PRO only) Furthermore, Audio Effects can be applied to the listener and it will be applied to all audible sounds in the scene.

The Audio Listener, attached to the Main Camera


The Audio Listener has no properties. It simply must be added to work. It is always added to the Main Camera by default.


The Audio Listener works in conjunction with Audio Sources, allowing you to create the aural experience for your games. When the Audio Listener is attached to a GameObject in your scene, any Sources that are close enough to the Listener will be picked up and output to the computer's speakers. Each scene can only have 1 Audio Listener to work properly.

If the Sources are 3D (see import settings in Audio Clip), the Listener will emulate position, velocity and orientation of the sound in the 3D world (You can tweak attenuation and 3D/2D behavior in great detail in Audio Source) . 2D will ignore any 3D processing. For example, if your character walks off a street into a night club, the night club's music should probably be 2D, while the individual voices of characters in the club should be mono with their realistic positioning being handled by Unity.

You should attach the Audio Listener to either the Main Camera or to the GameObject that represents the player. Try both to find what suits your game best.


Audio Source

The Audio Source plays back an Audio Clip in the scene. If the Audio Clip is a 3D clip, the source is played back at a given position and will attenuate over distance. The audio can be spread out between speakers (stereo to 7.1) (Spread) and morphed between 3D and 2D (PanLevel). This can be controlled over distance with falloff curves. Also, if the listener is within one or multiple Reverb Zones, reverberations is applied to the source. (PRO only) Individual filters can be applied to each audio source for an even richer audio experience. See Audio Effects for more details.

The Audio Source gizmo in the Scene View and its settings in the inspector.


Audio ClipReference to the sound clip file that will be played.
MuteIf enabled the sound will be playing but muted.
Bypass EffectsThis Is to quickly "by-pass" filter effects applied to the audio source. An easy way to turn all effects on/off.
Play On AwakeIf enabled, the sound will start playing the moment the scene launches. If disabled, you need to start it using the Play() command from scripting.
LoopEnable this to make the Audio Clip loop when it reaches the end.
PriorityDetermines the priority of this audio source among all the ones that coexist in the scene. (Priority: 0 = most important. 256 = least important. Default = 128.). Use 0 for music tracks to avoid it getting occasionally swapped out.
VolumeHow loud the sound is at a distance of one world unit (one meter) from the Audio Listener.
PitchAmount of change in pitch due to slowdown/speed up of the Audio Clip. Value 1 is normal playback speed.
3D Sound SettingsSettings that are applied to the audio source if the Audio Clip is a 3D Sound.
Pan LevelSets how much the 3d engine has an effect on the audio source.
SpreadSets the spread angle to 3d stereo or multichannel sound in speaker space.
Doppler LevelDetermines how much doppler effect will be applied to this audio source (if is set to 0, then no effect is applied).
Min DistanceWithin the MinDistance, the sound will stay at loudest possible. Outside MinDistance it will begin to attenuate. Increase the MinDistance of a sound to make it 'louder' in a 3d world, and decrease it to make it 'quieter' in a 3d world.
Max DistanceThe distance where the sound stops attenuating at. Beyond this point it will stay at the volume it would be at MaxDistance units from the listener and will not attenuate any more.
Rolloff ModeHow fast the sound fades. The higher the value, the closer the Listener has to be before hearing the sound.(This is determined by a Graph).
Logarithmic RolloffThe sound is loud when you are close to the audio source, but when you get away from the object it decreases significantly fast.
Linear RolloffThe further away from the audio source you go, the less you can hear it.
Custom RolloffThe sound from the audio source behaves accordingly to how you set the graph of roll offs.
2D Sound SettingsSettings that are applied to the audio source if the Audio clip is a 2D Sound.
Pan 2DSets how much the engine has an effect on the audio source.

Types of Rolloff

There are three Rolloff modes: Logarithmic, Linear and Custom Rolloff. The Custom Rolloff can be modified by modifying the volume distance curve as described below. If you try to modify the volume distance function when it is set to Logarithmic or Linear, the type will automatically change to Custom Rolloff.

Rolloff Modes that an audio source can have.

Distance Functions

There are several properties of the audio that can be modified as a function of the distance between the audio source and the audio listener.

Volume: Amplitude(0.0 - 1.0) over distance.
Pan: Left(-1.0) to Right(1.0) over distance.
Spread: Angle (degrees 0.0 - 360.0) over distance.
Low-Pass (only if LowPassFilter is attached to the AudioSource): Cutoff Frequency (22000.0-10.0) over distance.

Distance functions for Volume, Pan, Spread and Low-Pass audio filter. The current distance to the Audio Listener is marked in the graph.

To modify the distance functions, you can edit the curves directly. For more information, see the guide to Editing Curves.

Creating Audio Sources

Audio Sources don't do anything without an assigned Audio Clip. The Clip is the actual sound file that will be played back. The Source is like a controller for starting and stopping playback of that clip, and modifying other audio properties.

To create a new Audio Source:

  1. Import your audio files into your Unity Project. These are now Audio Clips.
  2. Go to GameObject->Create Empty from the menubar.
  3. With the new GameObject selected, select Component->Audio->Audio Source.
  4. Assign the Audio Clip property of the Audio Source Component in the Inspector.

Note: If you want to create an Audio Source just for one Audio Clip that you have in the Assets folder then you can just drag that clip to the scene view - a GameObject with an Audio Source component will be created automatically for it. Dragging a clip onto on existing GameObject will attach the clip along with a new Audio Source if there isn't one already there. If the object does already have an Audio Source then the newly dragged clip will replace the one that the source currently uses.

Platform specific details


On mobile platforms compressed audio is encoded as MP3 for speedier decompression. Beware that this compression can remove samples at the end of the clip and potentially break a "perfect-looping" clip. Make sure the clip is right on a specific MP3 sample boundary to avoid sample clipping - tools to perform this task are widely available. For performance reasons audio clips can be played back using the Apple hardware codec. To enable this, check the "Use Hardware" checkbox in the import settings. See the Audio Clip documentation for more details.


On mobile platforms compressed audio is encoded as MP3 for speedier decompression. Beware that this compression can remove samples at the end of the clip and potentially break a "perfect-looping" clip. Make sure the clip is right on a specific MP3 sample boundary to avoid sample clipping - tools to perform this task are widely available.

Audio Clip

Audio Clips contain the audio data used by Audio Sources. Unity supports mono, stereo and multichannel audio assets (up to eight channels). The audio file formats that Unity can import are .aif, .wav, .mp3, and .ogg. Unity can also import tracker modules in the .xm, .mod, .it, and .s3m formats. The tracker module assets behave the same way as any other audio assets in Unity although no waveform preview is available in the asset import inspector.

The Audio Clip inspector


Audio FormatThe specific format that will be used for the sound at runtime.
NativeThis option offers higher quality at the expense of larger file size and is best for very short sound effects.
CompressedThe compression results in smaller files but with somewhat lower quality compared to native audio. This format is best for medium length sound effects and music.
3D SoundIf enabled, the sound will play back in 3D space. Both Mono and Stereo sounds can be played in 3D.
Force to monoIf enabled, the audio clip will be down-mixed to a single channel sound.
Load TypeThe method Unity uses to load audio assets at runtime.
Decompress on loadAudio files will be decompressed as soon as they are loaded. Use this option for smaller compressed sounds to avoid the performance overhead of decompressing on the fly. Be aware that decompressing sounds on load will use about ten times more memory than keeping them compressed, so don't use this option for large files.
Compressed in memoryKeep sounds compressed in memory and decompress while playing. This option has a slight performance overhead (especially for Ogg/Vorbis compressed files) so only use it for bigger files where decompression on load would use a prohibitive amount of memory. Note that, due to technical limitations, this option will silently switch to Stream From Disc (see below) for Ogg Vorbis assets on platforms that use FMOD audio.
Stream from discStream audio data directly from disc. The memory used by this option is typically a small fraction of the file size, so it is very useful for music or other very long tracks. For performance reasons, it is usually advisable to stream only one or two files from disc at a time but the number of streams that can comfortably be handled depends on the hardware.
CompressionAmount of Compression to be applied to a Compressed clip. Statistics about the file size can be seen under the slider. A good approach to tuning this value is to drag the slider to a place that leaves the playback "good enough" while keeping the file small enough for your distribution requirements.
Hardware Decoding(iOS only) On iOS devices, Apple's hardware decoder can be used resulting in lower CPU overhead during decompression. Check out platform specific details for more info.
Gapless looping(Android/iOS only) Use this when compressing a seamless looping audio source file (in a non-compressed PCM format) to ensure perfect continuity is preserved at the seam. Standard MPEG encoders introduce a short silence at the loop point, which will be audible as a brief "click" or "pop".

Importing Audio Assets

Unity supports both Compressed and Native Audio. Any type of file (except MP3/Ogg Vorbis) will be initially imported as Native. Compressed audio files must be decompressed by the CPU while the game is running, but have smaller file size. If Stream is checked the audio is decompressed on the fly, otherwise it is decompressed completely as soon as it loads. Native PCM formats (WAV, AIFF) have the benefit of giving higher fidelity without increasing the CPU overhead, but files in these formats are typically much larger than compressed files. Module files (.mod,.it,.s3m..xm) can deliver very high quality with an extremely low footprint.

As a general rule of thumb, Compressed audio (or modules) are best for long files like background music or dialog, while Native is better for short sound effects. You should tweak the amount of Compression using the compression slider. Start with high compression and gradually reduce the setting to the point where the loss of sound quality is perceptible. Then, increase it again slightly until the perceived loss of quality disappears.

Using 3D Audio

If an audio clip is marked as a 3D Sound then it will be played back so as to simulate its position in the game world's 3D space. 3D sounds emulate the distance and location of sounds by attenuating volume and panning across speakers. Both mono and multiple channel sounds can be positioned in 3D. For multiple channel audio, use the spread option on the Audio Source to spread and split out the discrete channels in speaker space. Unity offers a variety of options to control and fine-tune the audio behavior in 3D space - see the Audio Source component reference for further details.

Platform specific details


On mobile platforms compressed audio is encoded as MP3 to take advantage of hardware decompression.

To improve performance, audio clips can be played back using the Apple hardware codec. To enable this option, check the "Hardware Decoding" checkbox in the Audio Importer. Note that only one hardware audio stream can be decompressed at a time, including the background iPod audio.

If the hardware decoder is not available, the decompression will fall back on the software decoder (on iPhone 3GS or later, Apple's software decoder is used in preference to Unity's own decoder (FMOD)).


On mobile platforms compressed audio is encoded as MP3 to take advantage of hardware decompression.

Page last updated: 2007-11-16