What was found
AIRCRAFT NOT GROUNDED: PILOT REPORTS LOUD 400 MHZ TONE BLEED THRU AUDIO, SAFETY OF FLIGHT MAKES IT DIFFICULT TO HEAR ATC IT APPEARS TO BE MIC JACK, IT APPEARS TO GO AWAY IF YOU PUSH DOWN ON MIC JACK. ALSO SEAMS TO HAPPEN WITH NOISE CANCELING HEAD SET. MAINTENANCE WAS UNABLE TO DUPLICATE DISCREPANCY USING DUAL PRONG BOOM MIC. SUGGEST REPLACING REU AS PRECAUTIONARY. A LATER FLIGHT 2319 REPORTS CAPTAIN HEADSET JACKS OPERATE NORMALLY. SUPPLEMENTAL INFORMATION: MAINTENANCE REPLACED CAPT HEADPHONE JACK (D6031) IAW WDM 23-51-11. OPS CHECK NORMAL IAW AMM 23-51-00. (CLOSED)