I am running a laptop with Ubuntu 12.10, and while flash files will play their video, I have absolutely no audio with them.
The problem was persistent when I was running 12.04, and I thought upgrading the OS would fix the problem, but it did not.
Other sounds play fine, such as mp3s, system sounds, speaker tests, etc.
I've installed flash using the
apt-get install flashplugin-installer command, and everything went smoothly. I use Firefox 18.0.1.