removeChild doesn't kill the audio in external swf (as3)

I am have several external swfs that get loaded into a container swf using addChild. Each time the user uses the navigation to select a new page I use addChild to swap out external swfs. This all works fine except a few of my external swfs have audio, and for some reason the audio keeps playing even when that swf has been removed and replaced with a new one.

I've looked all around for solutions and found several people with a similar issue, but no solution.