Maybe it's a limitation of then Chroms Cast extension, but I would be nice if it was possible to be able to select audio output, either to Chromecast or PC.
My TV doesn't have speaker and I have a bluetooth audio system connected to my PC.....would love to be able to use that :-)

Have you tried to play with the audio settings?

....does it change anything to change the audio settings?

If I set mine to AC3 I get no sound either.