A B757-200 CAPT RPTS THE R PACK RECIRCULATION MODIFICATION HAS INCREASED AIRFLOW AND NOISE IN COCKPIT. NORMAL CONVERSATION DIFFICULT.

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ACFT X IS TOO NOISY IN THE COCKPIT AND IT AFFECTS SAFETY. THE PROB IS DUE TO EXCESSIVE AIRFLOW INTO THE COCKPIT. IT'S LIKE WORKING IN A WIND TUNNEL WITHOUT EARPLUGS. ACFT X IS JUST ONE OF THE MANY B757'S THAT HAVE HAD A 'COA' ACCOMPLISHED; WHICH IS THE REPLACEMENT OF THE R RECIRCULATING FAN WITH A HIGHER OUTPUT B757-300 R RECIRCULATION FAN. I FULLY BELIEVE THAT THE HIGHER OUTPUT FAN BLOWS OUT THE BAFFLING IN THE CEILING DUCTWORK LEADING TO THE COCKPIT WHICH ALLOWS TOO MUCH AIRFLOW INTO THE COCKPIT. THERE HAVE BEEN SOME AIRPLANES WHERE THE OLD DUCTWORK HAS RUPTURED COMPLETELY. THE INCREASED NOISE MAKES NORMAL CONVERSATION AND CHKLIST READING BTWN PLTS DIFFICULT; INCREASES FATIGUE AND FORCES US TO RUN OUR RADIOS AT HIGH VOLUME LEVELS; THUS DAMAGING OUR HEARING. FOR A WHILE I CARRIED A SOUND LEVEL METER TO TAKE SOUND LEVEL MEASUREMENTS DURING CLB; CRUISE AND DSCNT ABOVE FL180 TO DOCUMENT THE DIFFERENCE BTWN B757'S WITH AND WITHOUT COA FANS. I FOUND THAT AIRPLANES WITH THE NEW FANS WERE SIGNIFICANTLY LOUDER; BY APPROX 2-3 DB. I WROTE UP ACFT X 'WITH R RECIRCULATING FAN ON EXCESSIVE AIRFLOW AND NOISE IN COCKPIT. NORMAL CONVERSATION DIFFICULT.' WHICH WAS SIGNED OFF WITH 'OPS CHK OK. NORMAL CONVERSATION CAN BE HEARD FROM BOTH COCKPIT SEATS.' OBVIOUSLY NOTHING WAS DONE TO ADDRESS THE PROB; SO I CONTACTED MAINT BY PHONE AND IT WAS SUGGESTED THAT THE NEXT TIME I FLY THE PLANE TO ADD MY SAFETY CONCERNS TO THE WRITE-UP. AFTER PUSHBACK ON THE NEXT FLT; I DETERMINED THAT ACFT X WAS STILL TOO NOISY AFTER ENG START; AND CONTACTED MAINT WHO PUT IN THE FOLLOWING WRITE-UP FOR US: 'FLT CREW RPTS AIR NOISE IN COCKPIT VERY LOUD FROM BOTH PACKS AND RECIRCULATING FAN. CREW CONSIDERS THIS A SAFETY CONCERN; UNABLE TO HEAR COM. TURNED OFF R PACK AND NOISE WAS REDUCED.' WE THEN DEFERRED THE R RECIRCULATION FAN AND FLEW TO ZZZ1. THIS TIME THE WRITE-UP WAS CLRED BY ZZZ1 MAINT WITH THE FOLLOWING; 'OK -- COM WITH GND AT ZZZ1 -- ABLE TO HEAR FROM BOTH SEATS.' AN ATTEMPT TO CONTACT TECHNICIAN TO ASCERTAIN HIS CRITERIA FOR JUDGING THE NOISE LEVEL OF ACFT X TO BE SAFE FOR FLT I SPOKE WITH A LEAD MECH AT ZZZ1. HE AGREED THAT B757'S ARE LOUD IN THE COCKPIT AND SUGGESTED THAT I CALL BACK FOR A SUBSEQUENT SHIFT TO CATCH TECHNICIAN. DURING MY CONVERSATION WITH LEAD MECH; HE SAID THAT MOST MECHS TURN OFF THE R RECIRCULATION FAN WHEN TAXIING B757'S BECAUSE 'YOU CAN'T HEAR.' BASED ON THE RESULTS OF BOTH MY RECENT WRITE-UPS; I SUSPECT THAT THIS ISSUE ISN'T BEING WRITTEN UP VERY OFTEN BECAUSE MOST CREWS KNOW NOTHING WILL BE DONE. NOTHING HAS HAPPENED YET FOR SURE! I AM MAKING A REPORT TODAY BECAUSE I THINK THAT THE LINE MECHS ARE PENCIL-WHIPPING MY WRITE-UPS; PLAIN AND SIMPLE. THEY HAVE NO BASIS TO JUDGE THE NOISE LEVELS AGAINST OTHER THAN THEIR PRESSURE TO CLR WRITE-UPS. ALSO; THEIR GND TESTING WITH APU AIR VERSUS OUR INFLT WRITE-UPS WITH BOTH ENGS RUNNING DEFIES ALL LOGIC. THE COMPANY IS ABOUT 1/2 WAY THROUGH FLEET-WIDE INSTALLATION OF COA WHICH WAS SUPPOSED TO FIX THE PROB OF FAILING R RECIRCULATION FANS. HOWEVER; DUE TO UNFORESEEN CIRCUMSTANCES OR INADEQUATE TESTING PRIOR TO COA ROLLOUT OR WHATEVER; THE COCKPIT CREWS ARE NOW SUBJECTED TO LEVELS OF NOISE THAT INCREASE FATIGUE AND DECREASE SAFETY. LINE MAINT IS NOT FIXING THE PROB.