What was found
DURING DESCENT BELOW PROFILE THRUST WAS APPROX 75 - 77% N1. AT PROFILE THROTTLES REDUCED TO IDLE & APPROX 60% N1, A THUMPING SOUND WAS HEARD & FELT. SUSPECT COMPRESSOR STALL. ALTITUDE 30000 FT SPEED 0.8. NO ABNORMAL ENG INDICATIONS. SUSPECT ENG NR 2. OLLOWED TSI 31-30 1377 INSPECTION IAW AMM 71-00-00-06. NO DAMAGE & NO METAL PARTICLES FOUND. PERFORMED FADEC GND TEST, BOTH ENGS IAW TSM 73-21-40, NO FAILURE RECORDED. REVIEWED THE DFDR DATA THAT AT FL 30 THE ACFT DID EXPERIENCE WIND DIRECTION & SPEED CHANGE. THEY BELIEVE THIS IS THE ROOT CAUSE OF BUFFETING THE FLIGHT CREW EXPERIENCED. THERE WAS NOT A COMPRESSOR STALL ON EITHER ENG. PERFORMED ACFT INSPECTION & CHECK IAW AMM 05-51-17-00 PHASE 1, NO DAMAGE, NO ABNORMAL FOUND.