ActionScript for Flash MX: The Definitive Guide, 2nd Edition By Colin Moock
Chapter 18. ActionScript Language Reference
stopAllSounds( ) Global Function
Flash 3
silence a movie
stopAllSounds()
Description
The stopAllSounds( ) function mutes all the sounds currently playing in a movie, no matter how deeply the sounds are nested in movie clips. This applies to every sound in a movie, including programmatically generated Sound objects. For more precise control over stopping, starting, and setting the volume of sounds, see the Sound class.
Note that stopAllSounds( ) has only a temporary effect. Any sound that starts after a stopAllSounds( ) invocation will play normally. Because button sounds are not controllable via the Sound class, there is no way to mute an entire movie permanently. However, a Player-wide Sound object with a volume of 0 will silence all nonbutton sounds.