you shouldn't attach sounds to frames. if you do, there are lots of ways to have problems.
to start, the sound isn't really sync'd to the time line unless you set the sound's sync property to stream.
I tried a couple of different methods (movie clips, etc), but this was one of the ways that ended up actully working... well, except for that unexplainable triggering when it hasn't ever reached the frame.
Sync isn't a huge issue here...I just need the sound to trigger, so that's why I did it the way I did.
Ultimately, I got it to work... but I never understood why the second or third audio would trigger, even though the frames they were on were never reached.
I know that it doesn't have absolute sync, but it's odd that the audio triggers when the first frame of it (or any of the frames after it) are reached... Like having a audio clip on frame 100, and a stop() on frame 50, and playing from frame 1 forward, and it triggers... even though the timeline successfully stops at frame 50.
Originally, I had a movie clip consisting of the video, the audio clip, and a code layer to stop it and have it load another page. On the _root timeline, I'd have one of the frames at the end of the main section have a label (say, 'LoadPage'), a stop() code, and an instance of the movie clip mentioned in the previous sentence. The theory was that if you send the timeline to that label, it would stop on that frame, but the movie clip that it is sitting on there would play (having an independent timeline). Got weird things happening doing that, and variations of it... like the audio playing, but not the video, or the audio of all the similar movieclips (separate on the main timeline) playing, even though only one of the movie clips was playing. Very odd...
How would you do it? Have the movie clip always on the stage, but have the first frame of that clip with a stop() so it doesn't play, and then do a movieclip.gotoAndPlay(2) when you want it to trigger? That's pretty much what I did in the end.
use the sound class to play sounds. you have much more control over sounds if you use the sound class and related classes.