I use a program called voicemeeter banana and it allows you to do this. It requires additional steps to get audio to the vive once you turn the headset on, but that's basically just refreshing your settings basically.
Voicemeeter is like a virtual mixer on the pc. You can have up to 3 audio inputs (mics) and 3 outputs. You can have a conversation with this by routing the mic of the vive to the pc speakers and the pc Mic to the vive.
It takes some fiddling to get used to the program.
Ive been looking for a better audio program. Will have to check this out.