Mmm… Yes, that might have something to do.
First thing would be to ensure that audio works when using the Pi directly.
I see that there are options to configure audio. You should verify that it is setup correctly:
Once you get sound when running from the Pi, you should verify how you need to start the vncserver.
Back when I used that, I had the machine automatically logging into an user and opening a session into the desktop. So then when I logged with vncclient, I was accessing that desktop.
I am assuming that the vncserver-virtual does not need an X session and instead emulates it. I don’t think this should affect sound in any way (because you want to talk to ALSA), but I have no idea, because I don’t have experience with that scenario.