Focusrite iDock buzzing noise when ipad swiped and other..

[miden]

Okay the iPAd 4 is connected to the iDock....when the iPad goes to the the active screen from the blank screen (black) when inactive there is a buzzing noise (I have an audio demo but can not upload it). It also happens if I swipe the screen. If I unattach and the reattach the iPad to the dock the sound disappears completely, only to re-occur at random intervals. In each case removing and replacing the ipad stops it???

Happens with the USB cable port in use and not in use so it is not that.

It really sounds like some sort of transformer buzz, so I want to ask other users if they experinence it or could it be a defective device?