MAINT CTL PRESSURES FLT CREW OF EMB TO FLY ACFT WITH LOUD AURAL WARNING FAULT REPEATING EVERY 3 SECONDS MAKING COM IMPOSSIBLE; FLT CREW REFUSES.

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WE RECEIVED AN ACFT FROM ANOTHER CREW AND DEPARTED LGA. IMMEDIATELY UPON GEAR RETRACTION; WE RECEIVED THE AURAL ALERT 'AURAL UNIT 1 CHANNEL' ONCE AND HEARD NOTHING FURTHER OF IT FOR THE REMAINDER OF THE FLT. DURING CRUISE FLT AFTER THE WORKLOAD DROPPED OFF; WE RPTED TO MAINT CTL OVER ATLANTA RADIO AND WERE TOLD IT WOULD BE HANDLED ON THE GND IN ILM. AT THE GATE IN ILM; WE OPS DEFERRED THE 'AURAL WARNING UNIT 1 CHANNEL' SINGLE MESSAGE PER THE MEL UNDER THE DIRECTION OF MAINT CTL AND DEPARTED BACK TO LGA. UPON WT-ON-WHEELS IN LGA; WE RECEIVED THE AURAL WARNING MESSAGE 'AURAL UNIT 1 CHANNEL' EVERY 3 SECONDS UNTIL MAINT ARRIVED AT THE ACFT AND PULLED THE SYS CIRCUIT BREAKERS MORE THAN 30 MINS AFTER LNDG. THE MESSAGE WAS RECEIVED ONLY IN THE FO'S HEADSET AND SPEAKER (AND; AFTER TROUBLESHOOTING; THE OBSERVER'S SEAT HEADSET AS WELL) AT A HIGH VOLUME. THE VOLUME WAS NOT CTLABLE AND DURING TAXI IN IT WAS VERY DIFFICULT TO MAKE THE NORMAL COORD BTWN OPS; RAMP; AND GND BECAUSE EVERY 3 SECONDS ALL THE FO COULD HEAR WAS 'AURAL UNIT 1 CHANNEL.' THE CAPT-SIDE SPEAKER AND HEADSET HAD A FAINT AND DISTORTED VERSION OF THE SAME MESSAGE; SIMULTANEOUS WITH THE OTHER HALF OF THE COCKPIT; BUT ALMOST INAUDIBLE. HOWEVER; DUE TO THE VOLUME OF THE MESSAGE; IT WAS ALSO VERY DIFFICULT FOR ME TO HEAR THE FO OR THE RADIO -- EVEN WEARING MY NOISE-CANCELING HEADSET. AFTER DEBARKING PAX; MAINT WORKED ON THE PLANE FOR ABOUT 20 MINS; RESETTING THE SYS MULTIPLE TIMES; DOING THE AURAL WARNING SYS CHK AND RE-RACKING THE AURAL WARNING UNIT. EACH TIME THE SYS WAS RESET AND RE-PWRED; THE MESSAGE PERSISTED. THE MECH TOLD US THAT MAINT CTL HAD DECIDED THE AIRPLANE WAS TECHNICALLY LEGAL FOR FLT. HE FURTHER SAID THERE WAS NO PART TO FIX THE SYS IN LGA AND THAT WE WOULD HAVE TO FLY THE ACFT TO THE MAINT BASE BECAUSE THE DEFERRAL OF THE SYS WAS STILL VALID AND THE AIRPLANE WOULD ENTER C-CHK WHERE THE PROB WOULD BE FIXED. I EXPLAINED THE SAFETY IMPLICATIONS OF TAKING AN AIRPLANE IN WHICH COMS WITH THE FO HAVE BEEN RENDERED INEFFECTIVE. THE FO COULD HEAR NEITHER ME NOR THE RADIO FOR 1 SECOND OUT OF EVERY 3; AND WOULD; THEREFORE; BE UNABLE TO CONCENTRATE ON FLYING. IN THE COURSE OF A NORMAL FLT THROUGH BUSY LGA AIRSPACE; OR IN THE EVENT OF AN EMER; HE WOULD BE UNABLE TO PERFORM ANY DUTY INVOLVING VERBAL COMS. I TOLD THE MECH HOW DISTRACTING IT WOULD BE TO THE FLT CREW; INCLUDING THE CAPT; SINCE THE AURAL WARNING SYS IS PRE-SET UNCHANGEABLE LOUD VOLUME. I TRIED TO MAKE IT CLR THAT THIS COULD LEAD TO AN UNSAFE SITUATION AND THAT I WOULD NOT FLY THE AIRPLANE WITH OR WITHOUT PAX. I AGREED THAT THE AIRPLANE WAS TECHNICALLY LEGAL; BUT DID NOT THINK THAT EQUATED TO MAKING IT SAFE BECAUSE OF THE CHANCE OF A DISTR FLT CREW MEMBER MAKING A MISTAKE. HE RPTED MY REFUSAL OF THE AIRPLANE TO MAINT CTL AND LEFT. I IMMEDIATELY CALLED DISPATCH; AND AS THE ACFT WAS STILL PWRED; I SAT IN THE FLT DECK FOR ALL PHONE CONVERSATIONS. THIS MEANT THAT ANYONE WITH WHOM I SPOKE CLRLY HEARD THE WARNING MESSAGE. I TOLD THE DISPATCHER THAT I WAS REFUSING THE AIRPLANE FOR SAFETY REASONS. THE DISPATCHER MENTIONED SHE COULD HEAR THE WARNING MESSAGE CLRLY OVER THE PHONE. A FEW MINS LATER; I RECEIVED A CALL FROM 3 FLT OPS MGRS ALL ON SPEAKERPHONE. I EXPLAINED THE SITUATION AND MY CONCERN FOR THE SAFE COMPLETION OF THE FLT WITH THIS DISTR IN THE COCKPIT. THEY SUPPORTED MY REFUSAL OF THE PLANE ON GROUNDS OF SAFETY; SAYING THAT EVEN A TEST FLT WOULD BE A BAD IDEA GIVEN THE CIRCUMSTANCES. AFTER SOME TIME AND SEVERAL PHONE CALLS; I SPOKE WITH DISPATCH WHO TOLD ME A PART WAS ON THE WAY AND OF OUR PROPOSED DEP TIME. DURING ONE OF THOSE CONVERSATIONS WITH MGMNT AND DISPATCH; I CAME TO UNDERSTAND THAT MAINT CTL HAD; ON THE GROUNDS OF LEGALITY; REFUSED TO PUT THE AIRPLANE OTS FOR 'MAINT;' SAYING INSTEAD THAT THE ISSUE WAS WITH THE CREW. I AM REASSURED THAT THE FLT OPS MGMNT STAFF UNDERSTOOD MY CONCERN AND SUPPORTED THIS DECISION; SHOWING THAT SAFETY IS A FUNDAMENTAL FOCUS OF OUR COMPANY.