Out of the box, Firefox STILL doesn\'t have support for playing embedded .wav.  Here\'s how to get \'er goin\':

You\'re going to need to install (or re-install) the mozilla-mplayer package.  I am using Mepis and Ubuntu (both Debian-based) so I just went into Synaptic Package Manager and did a search for "mplayer".  In the results are the packages "mplayer" and "mozilla-mplayer".  Just mark them both for installation and apply.  EASY!
or just from shell:
apt-get install mozilla-mplayer