What was found
CLIMBING OUT OF BWI TO OUR CRUISE ALT OF FL 360 HEARD A WHISTLE NOISE COMING FROM IN FRONT OF THE F/O SEAT WENT TO MONITOR PRESS ECAM-SAW CABIN ALT AT 900FT AND CLIMBING STOPPED CLIMB AT FL 310,CABIN CONTINUED TO CLIMB CABIN ALT GOT TO 9600,WE DESCENDED TO FLIGHT LEVEL 260.CABIN ALT CAME DOWN TO 8800 AND STABLIZED AS TIME WENT ON THE CABIN BEGAN TO CLIMB AGAIN VERY SLOWLY TO 9250.-R/R AFT CARGO DOOR SEAL IAW AMM 52-32-18.PERFORMED PRESURIZATION OF AIRCRAFT.NO LEAKS NOTED. OPS CK GOOD.AIRICRAFT IS AIRWORTHY FOR CONTINOUS SERVICE.