What was found
FLT# 751 JFK-JFK . "DURING CLIMBOUT AT 22000', L1 DOOR NOISE STARTED. VOLUME INCREASED AS ALTITUDE INCREASED. AT FL 340 NOISE WAS AS LOUD AS AN AIR RAID SIREN. HAD TO TALK VERY LOUDLY IN GALLEY 1 JUST TO HEAR EACH OTHER. SOUND WAS VERY LOUD IN COCKPIT AS WELL. WE ELECTED TO DESCEND, SOUND WENT AWAY AT FL 220 @7.3 PSI, 3000' CABIN ALT.; REF LOGPAGE 4597858 ITEM 1 REPLACED L1 DOOR SEAL PER AMM 52-11-18-400-001-A. CLEANED AND LUBRICATED NEW SEAL. PERFORMED THE PRESSURIZATION TEST OF AIRCRAFT WITH APU BLEED 05-52-00. NO LEAKS NOTED . NO ABNORMAL SOUND NOTED.