What was found
MAIN DOOR SEAL WILL SQUEAL AT A HIGH PITCH FROM APX 15,000 FT TO 24,000 FT FROM 24,000 FT TO 27,000 FT SQUEAL GETS FAINT & STOPS WITH NOISE CANCELING HEAD SETS ON AND CURTAIN CLOSED. DOOR SQUEAL IS LOUD WHEN INTERCOM IS SELECTED ON. MICROPHONE PICKS UP SQUEAL & IT IS HAD TO COMMICATE AS THE SQEAL BLEEDS ONTO HEADSET FO TRIED TO TROUBLE SHOOT. NOISE APPEARS TO BE COMING FROM UPPER LT CORNER OF AIRSTAIRS WHEN DOOR IS CLOSED. EVALUATE DOOR SEAL FOR NOISE ON CLIMB OUT NO SQUEAL NOTED ON DESENDING OPERATIONS. R & R MAIN DOOR SEAL IAW 52-11-28. OPERATIONAL CHECKS GOOD. NO HIGH PITCH SQUEALING NOTED.