As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE RT RECIRCULATION FAN IS PARTICULARLY LOUD ON THIS AIRPLANE. REF SERVICE TIP MM, ACCOMPLISHED STEP 6. TEST FAILED. REF STEPS 1 THRU 5 OF SERVICE TIP. ALREADY ACCOMPLISHED. ACCOMPLISHED DUCT CLEANING. DECIBEL READING WITHIN LIMITS. CFM 370 AND FPM 3357 WITHIN LIMITS AT THIS TIME. REPLACED LT FLOW CONTROL VALVE AND RECIRCULATION FILTERS.