Comment 66 for bug 148097

tonym:
I think you hit the same issue I did. Try adding:

pcm.builtin { type hw; card NVidia; device 3}
pcm.!default pcm.builtin

to your ~/,asoundrc

That fixed it for me. I'd be curious to know why some people it works fine out of the box and for others the sound config needs to manually modified.

Dewey:
For the question about getting the volume control to work: I don't think it's possible, the mixer doesn't have the option to be set to the hdmi specific device, only the hda nvidia generic one which doesn't seem to have any effect.

For anyone:
My current problem is no matter what I have tried, I have been unable to get sound to work within flash in firefox. If anyone has that working, I would be very appreciative to know how to do it.