Sounds like its working as intended? By default, your PC shouldnt be piping audio to the HMD unless Windows has the HMD set as the desired audio output device. If you leave Windows to ‘default’ audio device, it might not automatically trigger the change to HMD once it’s worn. You could also check in the Oculus app, click ‘Devices’ and then click your HMD to make the right-hand window open, then find options labelled ‘Hear VR audio from computer’ and ‘Hear computer audio in VR’ and toggle/untoggle these as desired.