The Audio Listener component is the equivalent
of your ears in the game.
It receives, or listens, to audio sources
that are in the game world.
The control of the audio's behaviour is done on
the audio source component
and therefore the listener itself has no settings.
This is attached to a camera in your scene by default
but can be placed on any object.
Often this is attached to a character
and crucially there can be only one listener
per scene in order for it to function correctly.
You can test an audio listener from any position in the world
by moving the scene camera around
with the audio preview toggle enabled.
This gives you live testing of audio sources
in your environment without having to move
the real listener or play test the game.
Audio sources are components that playback audio.
Think of them as speakers in the game world.
In this example our turbine has an audio source attached
with the turbine audio clip that's been applied to it.
We can assign a clip by dragging and dropping,
or by using code to select a clip to play.
We can mute, bypass any filters,
choose whether to play this audio source on awake,
as in - when the game begins
and whether to loop the clip.
Priority varies between 0 and 255,
0 being the highest priority.
It's advisable to have music set as the highest priority
to avoid other clips from overriding
when many clips are being played at once.
Volume determines how loud the clip is played
based on it's original waveform.
Pitch controls the pitch of a clip.
If you're working with 3D sounds
the settings are more detailed.
Doppler level defines how much the Doppler Effect
will be used.
This is a perceived shift in frequency as the listener
or the ear in real terms
is moving past the sound source.
It will seem higher approaching it
and lower as it moves away.
Think of an emergency vehicle's siren as it passes you
for example.
Volume roll-off determines the type of roll-off
to be used by the sound
as the listener moves away from it.
This can be logarithmic, linear,
or customised manually using a curve
and adding keys as shown.
The minimum distance defines how close
to play the sound at full volume.
So if you are designing 3D sound
use this value to make the sound source louder.
This can be adjusted using the spherical Gizmo
in the scene view.
And it works in the conjunction with the
maximum distance setting below,
which by default is set to 500 metres
and is a distance after which
the sound rolls off.
Pan level defines how truly 3D the sound is.
This defaults to 1 for 3D sound
making it fully panned when the stereo listener
is moved past it.
Spread is the control of the angle of spread
from 3D stereo to multichannel sound.
Finally for 2D sound pan can be controlled
at the bottom of the component.
As a rule elements such as music
should be set to 2D sound,
whilst diegetic sound that should be
fading realistically should be set up
as 3D and positioned accordingly.
The 2D and 3D values of a sound
are controlled by an audio clip's import settings.
When selecting a clip in the project
you will be able to see the import settings
in the inspector.
You can choose the audio format to use,
whether it should be 3D or 2D sound,
whether you want to force your stereo sound to mono,
how to load it and what compression to use.
You can also preview sound at the bottom,
choose whether to loop whilst previewing
and set the inspector to auto-play
whilst browsing through clips.