This was mentioned when YouTube started doing this but some of the comments here don't seem to be aware of it. Chrome will indicate when sound is playing right

This was mentioned when YouTube started doing this but some of the comments here don't seem to be aware of it. Chrome will indicate when sound is playing right now if you add "–enable-audible-notifications" to the commandline (easier done on Windows than MacOSX) and even works for sound coming from Flash plug-ins. Of course since it requires a commandline to work, there are likely some issues associated with it (but it has worked fine for me.) Once this feature no longer requires a commandline, this idea will still be useful for people who use other browsers.