The volume level applies to the items with sound played back on Scene and the Speak, Play Sound, and Repeat Sound System actions.
To adjust playback volume, use one of the following:
•Click-and-drag the Volume Slider to the right of the Timeline.
•Use a Mouse Wheel by clicking on the slider.
•Use Ctrl+Up or Ctrl+Down over the slider.
You can also click the speaker icon to mute or unmute audio (keyboard shortcut: U).