When a constant buzzing sound is emitted when no sound is playing, but the buzzing goes away during playback, this could be an issue with the device not liking to be suspended when not in use and thus 'unowned'. This can be sorted by disabling the suspend functionality. A different driver/kernel module may fix the underlying issue:

sudo vi /etc/pulse/default.pa

# comment out the following line:
load-module module-suspend-on-idle

Save and exit, then restart pulseaudio as user:

pulseaudio -k