As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THRU 12000 FT GOT VERY LOUD SQUEAL. NO CONTROL OF CAPTAINS MIC S ELECTOR CONSTANT BLARING NOISE. ADD PHOTO PANEL, AUDIO SE OFF 29-2351-9-0003 1881 ON 0000 PANEL, AUDIO SE OFF 29-2351-9-0003 1881 ON 29-2351-9-0003 4894 DEBRIEFED CREW: EXPERIENCED LOSS OF CAPT AUDIO CONTROL PANEL & NOISE STOPPED BEFORE RETURN TO GATE. REPLACED CAPT AUDIO CONTROL PANEL MM23-51-02 & INSTALLED NEW MINITEL. OPS TEST FROM BOTH POSITIONS, COM 1&2, & CAPT O2 MASK ALL OK. TAXIED AIRCRAFT & OPERATIONAL TESTS ALL OK. NO SQUEALING NOTED.