YouTube sound does work on the MacBook in Safari. It also works on my Motorola Droid smart phone. And it works on my iPad. (Is that what "Don Jon" means by "My Pad"?)
Did Google make a server change that somehow doesn't recognize Windows sound drivers for videos\?
Vimeo does work in these browser in Windows. Just try this in Windows 7 or 8, link.
Private setups that don't use YouTube for video work in Firefox (and everything else) in Windows. Try IgigiStudios, typical music video, here. Or try Timo Andres (composer), for example, here. At least, my own followers know some of my favorite video and music sites and artists.
My own mp3 files (of my own music) work in all environment (standalone, from my "doaskdotell.com" website as explained on my "drama" blog Oct. 5).
What hath YouTube done to us?
Back in March 2012, embedded YouTube videos stopped working for about half a day on a Saturday while I was in New York City, for everyone. Expanded YouTube embeds (introduced a few months ago) do not seem to work on the iPad even now. I don't know why/