What was found
AIRCRAFT WAS GROUNDED: AT DOOR 1L, AFTER TAKEOFF, LOUD NOISE PREVENTED COMMUNICATION WITH FORWARD CABIN. AIR RETURNED TO DFW, NO EMERGENCY DECLARED. FLIGHT LANDED SAFELY WITHOUT FUTHER INCIDENT. MAINTENANCE CLEANED AND ADJUSTED L1 DOOR SEAL PER 52-09-10, PRESSURIZED AIRCRAFT, AND PERFORMED SATISFACTORY OPERATIONAL CHECK.