> Even using the Windows volume mixer to mute Firefox doesn't stop the noise.
Seems like this is a deeper bug than FF then, no?
Not necessarily. Modern Windows lets you create a new mixer/mediasource separate from the app, so you can have Your regular app sounds then separate media(or notification) sounds.
I use the extension on desktop without problems. I guess it depends on what websites you visit. I would disable the extension for ones that do play/stop sounds a lot.
The tab doesn't show the "playing" icon, and muting the tab doesn't stop the noise.
Even using the Windows volume mixer to mute Firefox doesn't stop the noise.
Edit: The addon is actually pretty bad for a desktop user since the white noise starting/stopping constantly is far more annoying.