What was found
SLC - AIR TURN BACK - ON CLIMB OUT FROM SLC EN ROUTE FOR PHX FLIGHT ATTENDANT REPORTED AN EXTREMELY LOUD NOISE AND VIBRATION IN FLOOR BOARDS OF AFT CABIN, TURNED BACK TO SLC AND LANDED WITHOUT FURTHER EVENT. MAINTENANCE PERFORMED GROUND INSPECTION OF FUSELAGE INCLUDING ALL SERVICE PANELS AND ACCESS DOORS. INSPECTED RUDDER POWER CONTROL UNITS FOR WEAR AND ABNORMAL CONDITIONS; INSPECTED THE STABILIZER, APU DOOR, AND APU MOUNTS. INSPECTED HELL HOLE AFT OF AFT PRESSURE BULKHEAD, NO DEFECTS WERE NOTED. INSPECTED THE AFT CARGO COMPARTMENT PANELS, THE ENGINE INLET & TURBINE BLADE AREAS, AND THE LANDING GEARS, NO DEFECTS NOTED. INSPECTED THE SLATS AND FLAPS FOR LOOSE FAIRINGS, AND ABNORMAL PLAY, NO DEFECTS FOUND. INSPE