When I go to clip my mains powered clipper it produces a loud noise?

This means the blades require oiling or your power screw located on the right hand side of the clipper requires adjusting.

To adjust this, plug in the clipper and  turn it on, then turn the power/voltage screw anti-clockwise until the noise subsides to a standard running noise, then carry on and adjust it a further quarter of a turn. If adjusted correctly this should have solved the problem. Alternatively please refer to your instruction booklet.