vorpX per default tries to set sound output to the headset when launching a game. Maybe that doesn’t work right in your case for some reason. This feature isn’t really needed anymore anyway admittedly, basically a leftover from the very early days of Oculus. I should probably remove it, all headset runtimes handle that by themselves these days.
You can disable it on the ‘General’ page of the config app and let SteamVR handle audio on its own. If it still doesn’t work afterwards, check the according SteamVR options, which let you select a device you want to use if auto-switching fails.