When Do Not Disturb mode is activated, notifications are not visible, but any tab of the browser open on a social network may produce an audio notification. It should be nice to have a way to mute these brower tabs when switching to this mode.
Unfortunately there's not really a way to tell what kind of sound it is. There is a "sinkId" property on HTML Audio which is documented as "This ID should be one of the MediaDeviceInfo.deviceId values returned from MediaDevices.enumerateDevices(), id-multimedia, or id-communications." but I haven't seen that used anywhere yet.