What was found
CLIMBING THROUGH FL200, AN EXTREMELY LOUD SQUEAL NOISE FROM CA S SIDE STARTED. CONTINUED CLIMB AND LET THE AIRCRAFT CONTINUE TO PRESSURIZE TO SEE IF NOISE WOULD SUBSIDE. PRESSURIZATION WAS NORMAL THE WHOLE TIME. THE NOISE WAS CONSTANT MAKING IT VERY DIFFICULT TO COMMUNICATE. RETURNED BACK TO MEM AND ON DESCENT THROUGH 18000FT-16000FT THE NOISE STOPPED. AFTER FINDING THE NO 2 LH WINDOW PRESSURE SEAL TO BE CUT.COMPLETED THE INSTALLATION OF THE NO 2 LH WINDOW PRESSURE SEAL. SEALANT CURING PERFORMED CABIN PRESSURIZATION CHECK REF B757 AMM ABOVE. NO LOUD SQUEALS NOTED ON CAPTAIN'S SIDE.