What was found
DURING CRUISE FLIGHT, AT FL380 AN AUDIBLE SQUEAL WAS HEARD AT THE MAIN ENTRY DOOR. THE CABIN RATE OF CLIMB STARTED TO INCREASE AND THE PASSENGER OXYGEN MASKS WERE DEPLOYED. AS THE CREW DONNED THEIR MASKS ATC AUTHORIZED AND EMERGENCY DESCENT AND DIVERSION. THE CABIN HIGH LIGHT ILLUMINATED DURING DESCENT. TROUBLESHOOTING FOUND 10 PSI AT THE MAIN ENTRY DOOR SEAL. FULL SERVICE AIR PRESSURE FOR DOOR SEAL INFLATION SHOULD BE 23PSI.