What was found
AT 31,000 FEET LOST 5% N1 ON RIGHT ENGINE WITH SLIGHT YAW. LASTED 2-3 SECONDS, THEN CONDITION CORRECTED ITSELF WITH NO INPUT FROM THE CREW. N1 WAS SET TO 85 % AT TIME OF ROLLBACK, AND SPEED SWITCHES WERE SELECTED ON. NO ABNORMAL CAUTIONS OR MESSAGES PRESENT DURING ROLLBACK. THE REST OF THE FLIGHT WAS UN-EVENTFUL, DECLARED EMERGENCY. DID NOT NOTICE FLUXUATION IN ANY OTHER SETTINGS OR PERAMETERS. DURING POWER ASSURANCE RUN AND ACCELERATION, DECELERATION CHECK NOTED AND AUDIBLE HISSING OR BLOWOFF NOISE FROM RIGHT ENGINE.