As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOUD NOISE THAT APPEARED TO COME FROM THE CAPT'S SLIDING WINDOW AREA. A VIBRATION COULD BE FELT ON THE POST IN THE WINDOW ARM. BUT COMMUNICATION WAS NEARLY IMPOSSIBLE WITH ATC. EVENTUALLY AN EMERGENCY WAS DECLARED. LOWER ALTITUDE AND LOWER AIRSPEED HELPED. NOISE REMAINED UNTIL DESCENT BELOW 19,000 FT AND FL 270. REMOVED AND REPLACED CAPTS SLIDING WINDOW FRAME INNER SEAL.