It is logical to expect the volume up/down buttons on my USB headphones to only control the volume of the headphones, but in fact they also unmute all other audio output devices. I'm using KDE on Fedora 23. How can I obtain the expected behaviour?
The reason I want to do this is because I don't want Thunderbird/Slack/etc. notifications to come through my laptop's speakers. Incidentally, pavucontrol shows that "System sounds" are muted, but this doesn't affect Thunderbird notifications, which still make a sound when the main audio output is unmuted - I guess they aren't considered "system sounds".