EE WAS TRYING TO CLEAR MUD FROM A DRILL BIT ON A DOWN THE HOLE ENCLOSED CAB DRILL. WHEN THE EE STEPPED OUTSIDE OF THE CAB TO PLACE THE PLATE IN PLACE TO DISCONNECT THE DRILL BIT, THE MUD CLOG RELEASED THE BUILT UP PRESSURE. EITHER THE OVER PRESSURE AIR OR THE LOUD NOISE CAUSED DAMAGE TO HIS EARS. INFLAMMATION AND TRAPPED FLUID CAUSED A HERARING LOSS.