Every time I go to my volume mixer, Firefox is constantly acting as if it's playing sound from a video or something. I don't actually hear anything, and I still see it if I have no sound actually playing. I've just realized that it's clearly not actually being sent to my speakers since the master volume is not displaying anything, but what is this hidden sound? To be clear, the sound itself works fine when it's actually supposed to play something. I'm just concerned by this constant silent sound.