What was found
F/A REPORTS THAT R2 DOOR MAKES LOUD, HIGH PITCHED NOISE DURING FLIGHT. ALL PRESSURIZATION INDICATIONS ARE NORMAL. F/A REPORTS THAT IT WAS VERY LOUD ON DESCENT AND INTERFERED WITH COMMUNICATIONS. ACFT GROUNDED. PRESSURIZED AIRFRAME TO 4 PSI, HIGH HISS ON INSIDE ON LOWER CENTER OF DOOR R-2 CONFIRMED BY LEAK CHECK ON OUTSIDE LOWER CENTER OF DOOR & ON AFT LOWER DOOR, WHERE DOOR MEETS SILL. FOUND ANTI-SKATING FOIL DAMAGE ON OUTFLOW VALVE REPAIRED ANTI-SKATING FOIL ON OUT FLOW VALVE. REF AMM 21-31-03-400-801, STEP 3.F.4, PRESSURIZED ACTUATOR TO 4 PSI NO LEAKS NOTED ON R2 DOOR.