The men's game (and perhaps the women's too, not sure) will be carried live on a free app called The Varsity Network, so if the men's game is not carried on that station, you could listen that way.
Another option: Soonersports.com has the audio feed for tonight's game. I don't know if it's for paid members only, but being audio-only, I wouldn't think so. I don't know for certain, though.