What was found
IMMEDIATELY AFTER TAKE OFF, FLT 3032, MAIN DOOR MADE VERY LOUD NOISE. AIR RETURN TO MEM. MAINTENANCE FOUND STICKER ON MAIN DOOR FRAME MATING SURFACE WHICH CAUSED MAIN DOOR TO NOT SEAL PROPERLY. INSPECTED MAIN DOOR SEAL AND DOOR FRAME SURFACE, NO FURTHER DISCREPANCIES NOTED. RAN AND PRESSURIZED A/C, NO NOISES HEARD FROM MAIN DOOR, NORMAL PRESSURIZATION OCCURED A/C RTS.