What was found
LOUD NOISE FROM CABIN DOOR AT FL370. FOUND DOOR SEAL TO BE THE CAUSE. ALERTED ATC FOR LOWER ALTITUDE. NO PRESSURIZATION PROBLEMS INDICATED, HOWEVER PRESSURIZATION CONTROLLER BEGAN TO FLUCTUATE. CREW DONNED THEIR O2 MASKS, DECLARED AN EMERGENCY DESCENT AND DIVERTED. MAINTENANCE INSPECTED, CLEANED, AND LUBED PASSENGER DOOR SEAL. FOUND SEAL AND SEAMS NOT CONNECTED, RECONNECTED SEAL ENDS IAW MM. FOUND INNER OR PRIMARY SEAL GOOD. LEAK CHECK GOOD.