What was found
AIR INTERRUPT, L1 DOOR HARD TO CLOSE AT GATE. UPON TAKEOFF & CLIMB TO FL250 FLIGHT ATTENDANT REPORTED LOUD NOISE AS IF AIR RUSHING OUT AT UPPER HINGE POINT. RETURNED, LANDING UNEVENTFUL, EMER NOT DECLARED & ACFT NOT OVERWEIGHT. INSPECTED DOOR HINGE AREAS & OPERATING MECHANISM IAW AMM 52-11-00. OPERATIONS CHECKED DOOR IAW AMM 52-11-00. INSPECTED DOOR SEAL IAW AMM 52-09-00. ACCOMPLISHED CABIN PRESS LEAK TEST IAW AMM 05-51-91. NO LEAKS NOTED. SYS CHECKED NORMAL.