To access audio settings, hit the TAB key or click on the APPS button and select the Settings option on the menu wheel.
From here, select the small speaker tab/icon on the window that appears (the seventh tab along the top).
The options function as follows:
MUSIC : This slider changes the volume of music, if any is present. Music is not normally present.
NPC DIALOGUE : This slider changes the voice volume of AI characters.
VOIP [RECEIVED] : This slider changes the volume of incoming voice chat.
AMBIENT : This slider changes the volume of environmental background sounds. None are normally present.
USER INTERFACE : This slider changes the volume of the user interface interaction sounds.
TEXT-TO-SPEECH : This checkbox enables / disables text-to-speech, and the slider modifies its volume.
ENABLE TEXT-TO-SPEECH SYSTEM MESSAGES : This checkbox sets whether system messages are ‘spoken’.
GENERAL SFX : This slider controls miscellaneous sounds.
ENABLE AVATAR VOIP RADIUS : This checkbox enables / disables directional and positional voice chat sound (sound that emanates from an avatar). The default is set to off, allowing for voice chat to function ‘globally’ in that 3D world.
ENABLE VOIP RADIUS VISUALISATION : This checkbox enables / disables a radius display around avatars to show how far their voice carries when positional and directional voice chat is active.
VOIP RADIUS VISIBILITY MODIFIER : This setting allows you to control which set of avatars have voice chat radius displays around them.