DC9 CREW WITH SIMILAR CALL SIGN TRIES TO SORT OUT CLRNCS BTWN CTLRS AND OTHER FLCS AS MULTIPLE CLRNCS ARE GIVEN AND RECEIVED BY WRONG CREW.

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NOT LONG AFTER CHKING IN WITH GSO APCH; WE APPARENTLY UNDERSTOOD A CLRNC GIVEN TO ANOTHER ACFT WAS INTENDED FOR US. THE FO READ BACK THE CLRNC (THE EXACT CLRNC I DO NOT REMEMBER) AND THE CTLR SAID 2 ACFT ANSWERED THE CLRNC; AND REISSUED THE CLRNC TO AN ACR ACFT; FLT XXX. I DID NOT IMMEDIATELY NOTICE THE SIMILARITY BTWN THE CALL SIGN/FLT NUMBERS OF THE ACR XXX AND OURS (ACR 2 AXXX). APPARENTLY; THE CTLR DID NOT REALIZE THAT THE CALL SIGNS; WHEN SPOKEN; SOUND ALMOST IDENTICAL; BECAUSE HE DID NOT ALERT US OF THAT FACT. WE CONTINUED ON OUR ASSIGNED HDG (DOWNWIND RWY 32 AT GSO) AND ALT (4000 FT MSL). THE APCH CTLR THEN ADVISED THAT WE WERE DOWNWIND RWY 32. A FEW MOMENTS WENT BY; THEN WE RECEIVED FROM THE APCH WHAT WE INTERPED AS CLRNC FOR A VISUAL APCH FOR RWY 32. MY FO READ BACK THE CLRNC; AND I BEGAN DSCNT TO 3000 FT AGL AND INITIATED AN APPROX 20 DEG R TURN TO BEGIN TURN TO BASE. THE APCH CTLR THEN ADVISED US THAT WE SHOULD BE ON A HDG OF XX DEGS AND 4000 FT. I IMMEDIATELY CORRECTED HDG AND ALT AND BEGAN TO QUESTION THE COM ERROR. I HEARD THE VISUAL APCH CLRNC REPEATED. I THEN REALIZED THE SIMILARITY BTWN THE 2 CALL SIGNS. CONCLUSION: REVIEWING THE SIT; I CAN CONCLUDE THAT ALL 3 PARTIES -- MY FO AND I; ACR XXX; AND THE APCH CTLR; AT SOME POINTS DURING THIS TIME PERIOD; MISINTERPED CLRNCS AND/OR READBACKS OF THOSE CLRNCS DUE TO THE SIMILAR SOUNDING CALL SIGNS: ACR XXX AND ACR 2 AXXX. THE CTLR WAS THE PARTY TO FIRST RECEIVE INFO AND HAD KNOWLEDGE OF THE SIMILAR CALL SIGNS; BUT FAILED TO ALERT THE 2 FLCS. CONTRIBUTING FACTORS ARE THE HIGH WORKLOAD OF THE CTLR AND FLCS DURING THIS CRITICAL PHASE OF FLT; IE; RECITING CHKLISTS; LOOKING FOR TFC; SCANNING OUTSIDE TO LOCATE THE ARPT VISUALLY.