What was found
IAH - DURING APPROACH INTO IAH, THE NR 1 ENGINE VIBRATION READING ROSE TO 2.5 WITH NOTICEABLE AIRFRAME VIBRATION. PER PROCEDURES, PLACED NR 1 THRUST LEVER TO IDLE AND VIBRATION STOPPED. AFTER TURNING ON ENGINE HEAT, RESET THROTTLE TO MATCH NR 2 SETTING AND VIBRATION ON NR 1 ENGINE REACHED 2.8. PULLED BACK TO IDLE AND LANDED. ALL OTHER INDICATIONS NORMAL. AN EMERGENCY WAS DECLARED. MAINTENANCE RAN NR 1 ENGINE. NO DEFECTS NOTED. AIRCRAFT OK FOR SERVICE. VIBRATION INDICATION SYSTEM CHECKS GOOD. REFERENCE MM 71-00-00-735-013-C00.