I’m sorry to hear you’re having trouble with your Qu!
The first thing to make sure is whether the Qu is producing this noise. You can do this buy changing output sockets, cables, speakers to see if the behaviour changes.
If it’s definitely the Qu causing the noise, please contact your distributor to arrange a service.
We will need some more info on your setup and what you have done to kind of narrow down the problem.
Did it just start happening, Is the QU mixer new to the system replacing another mixer?
If your using powered speakers make sure they are not set in the mic input level mode, they would need to be in line level mode.