HP revolve with Monitor speakers has a static noise

HI

I have an hp revolve 810 with an hp slim dock. Whenever i connect the aux from the dock to the monitor there is a static noise on the Monitor Speakers (audio is fine though). Even when the audio in Windows is off the noise continues.

The noise is not present when i connect my phone to it. 

i've switched the docking station, the aux cable, the monitor and tested it with another hp revolve 810 and the noise is still there.

Thanks for any suggestions