No Sound Fix for Your Embedded YouTube Video
Sometimes the embedded (chromeless) YouTube player will fall silent on video playback for an apparently unexplained reason, with no immediate way to fix. I think it has to do with YouTube/flash caching muted sound settings from youtube.com or other non-chromeless player and somewhere along the way these are carried over to your chromeless video.
thus guaranteeing sound playback regardless of previous state. Similar solution for Actionscript. Further API details at http://code.google.com/apis/youtube/js_api_reference.html