This happens on both my Windows 10 systems, a late 2012 iMac and a custom-built PC using an ASRock Z170 motherboard and an Insignia Bluetooth dongle.
When using either Discord or Mumble and either Apple AirPods or a Bose QuietComfort 35 headset, I cannot hear sound from any other application unless I set the output device to the "Hands-Free Device" instead of the "Stereo Headphones" device.
The problem with that is the "Hands-Free Device" has only one sound quality option, 8 KHz, which is nowhere near the 44.1 KHz default of the "Stereo Headphones" output device. When I select the "Stereo Headphones" device the sound is great, until I open either of the mentioned voice chat applications, whereupon I can't hear anything until I close that program. Also, my mic does not work unless I re-set the communications device or default device to the hands-free option. If I set the hands-free device as the communications device, everything in the voice chat app works, but no other program has any sound.
I believe this is because the "Hands-Free" and "Stereo Headphones" devices are two separate Bluetooth services, and the Hands-Free device is activated whenever the voice chat is engaged, and remains that way until the "call" is over. I realize the "Communications" tab in the sound control panel is supposed to fix this sort of thing, but it changes nothing in this scenario.
EDIT: I've read the suggestions in this post, which I just discovered, and none of that works:
- Removing the Hands-Free Telephony service removes the mic.
- Changing the "Exclusive Mode" setting on any playback or recording device does not resolve the problem. Sometimes it does temporarily, then it reverts back to the problem described above within 5 minutes or so.
- Disabling audio enhancements does nothing.