Flash MX 2004.
frame.soundLoopMode
Property; a string that specifies whether a sound that is attached directly to a frame (frame.soundLibraryItem) should play a specific number of times or loop indefinitely. Acceptable values are "repeat" and "loop". To specify the number of times the sound should play, set a value for frame.soundLoop.
The following example specifies that a sound should play two times:
fl.getDocumentDOM().getTimeline().layers[0].frames[0].soundLoopMode = "repeat";
fl.getDocumentDOM().getTimeline().layers[0].frames[0].soundLoop = 2;