MD80 REPEATEDLY PRODUCES UNIDENTIFIED LOUD; HIGH-PITCHED NOISE NEAR FA JUMPSEAT. MAINT COULD NOT DUPLICATE AND SIGNED OFF ACFT; ONLY TO HAVE IT HAPPEN AGAIN ON SUBSEQUENT LEG. ACFT WAS THEN TAKEN OUT OF SERVICE.

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DURING CLB ON 2 CONSECUTIVE LEGS; 2 DIFFERENT FLT ATTENDANT CREWS RPTED A LOUD; HIGH-PITCHED NOISE IN THE FORWARD OR 'A' FLT ATTENDANT JUMPSEAT AREA. ON THE FIRST LEG; I DON'T RECALL HEARING ANYTHING UNUSUAL IN THE FLT DECK; DESPITE THE FLT ATTENDANT'S RPT OF NOISE ON CLB. ONCE WE ARRIVED IN ZZZ AN ENTRY WAS MADE IN THE MAINT LOGBOOK AND MAINT WAS SUMMONED TO THE AIRPLANE. I DID NOTICE THAT A WRITE-UP FOR THE SAME ISSUE HAD BEEN PREVIOUSLY ENTERED INTO THE MAINT LOGBOOK SEVERAL DAYS EARLIER; SO MY WRITE-UP IN ZZZ WAS THE SECOND WRITE-UP FOR THE SAME ISSUE IN A SPAN OF JUST A FEW DAYS. MAINT PRESSURIZED THE PLANE AT THE GATE TO BTWN 4-5 PSI DIFFERENTIAL CABIN PRESSURE AND NO NOISES WERE NOTED. THE PLANE WAS SIGNED OFF AND WE DEPARTED WITH A DIFFERENT FLT ATTENDANT CREW. WHILE CLBING OUT OF ZZZ; THE NOISE RETURNED AND THIS TIME IT WAS LOUD ENOUGH TO BE HEARD IN THE FLT DECK. MAINT WAS NOTIFIED THAT THE PLANE WAS GOING TO BE WRITTEN UP AGAIN ON ARR. AFTER LNDG; THE PLANE WAS WRITTEN UP AGAIN (THE SECOND TIME IN 2 CONSECUTIVE LEGS FOR US AND THE THIRD TIME COUNTING THE WRITE-UP FROM SEVERAL DAYS EARLIER.) 3 MECHS CAME OUT TO TROUBLESHOOT THE NOISE AND ULTIMATELY THE DECISION WAS MADE TO EQUIP SUB THE NEXT FLT WHICH WAS ORIGINALLY SCHEDULED TO BE DONE USING THIS ACFT. ACCORDING TO THE MECHS; THERE WAS A LONG HISTORY ON THIS LOUD; HIGH-PITCHED NOISE THAT WAS MUCH MORE THAN JUST THE 3 WRITE-UPS WE WERE AWARE OF. ALL 3 MECHS REFUSED TO SIGN OFF THE AIRPLANE CONSIDERING ITS HISTORY AND I APPLAUD THEIR DECISION TO DO THE RIGHT THING AND HAVE THE AIRPLANE FIXED. AS OF THIS SAFETY RPT; THE PLANE WAS FERRIED TO ZZZ1 AROUND XA30 ON JUL/XA/07 AND THE NOISE AGAIN RETURNED DURING THE FERRY FLT. IT'S MY UNDERSTANDING THAT THE PLANE IS NOW SCHEDULED FOR A MAINT TEST FLT IN HOPES OF DETERMINING THE SOURCE OF THE NOISE JUL/XB/07. WITH THIS KIND OF HISTORY ON THIS JET; I'M WONDERING WHY THE PLANE WAS EVER PLACED INTO REVENUE SVC FOR FLTS XXX AND YYY; ESPECIALLY WHEN THE COMPANY MUST HAVE OBVIOUSLY BEEN AWARE OF THE HISTORY ON THIS PLANE. HAD I BEEN AWARE OF SUCH A HISTORY; I WOULD HAVE NEVER ACCEPTED THE AIRPLANE FOR THE 2 LEGS WE FLEW IT. I'M GREATLY CONCERNED TO SEE ONGOING MAINT ISSUES REGULARLY SIGNED OFF JUST TO KEEP A PLANE IN SVC DESPITE PROBS THAT SHOULD GND A PLANE. IT'S BECOME QUITE COMMON IN THE PAST FEW MONTHS TO SPEND A LARGE AMOUNT OF MY TIME AT WORK DEALING WITH BROKEN MD80'S. THESE ISSUES CERTAINLY DO NOTHING FOR MY CONFIDENCE IN THE MAINT AND RELIABILITY OF OUR MD80'S AND IT GIVES A DEFINITE IMPRESSION THAT THE COMPANY IS NOT MAINTAINING THE MD80'S AS THEY SHOULD.