What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED DUE TO: LOUD KNOCKING NOISE HEARD FROM RIGHT SIDE OF COCKPIT AFTER TAKEOFF. LOUD ENOUGH TO BE HEARD FROM CABIN; AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT CLE. CONFIRMED GROUND POWER SERVICE DOOR FOUND OPEN AND GROUND COMMUNICATION HANDSET STILL CONNECTED. REMOVED GROUND COMMUNICATION DEVICE AND CLOSED DOOR. ACCOMPLISHED GVI NO FRUTHER FAULT FOUND.