If one switches users (i.e. user one switches off, and then another users logs in) and there is sound playing on the first user, that sound will continue to play for the second user.
If the second user has admin rights, they can guess what program is causing the sound and then kill it, but that is very clumsy, and far more than what "needs" to be done.
When I open the mixer, it just shows that sound is playing. How can I stop it?