EMPLOYEE WAS WALKING ON CATWALK IN CLEAN COAL SILO. A NORFOLK/SOUTHERN TRAIN LOCOMOTIVE WAS LOCATED IN THE SILO. WHEN THE TRAIN PREPARED TO MOVE THE TRAIN ENGINEER BLEW HIS WHISTLE. THE SOUND OF THE WHISTLE CAUSED EAR RINGING (TINNUITIS) FOR THE EMPLOYEE. HE WENT OFF WORK ON 1/21/03 FOR TESTING ETC.