Narrative:

I was working a combined sector at HUD/det. I had reports from ZAU that aircraft couldn't hear me/I couldn't hear them; so I was moving from mains to standby then finally to buec [back up emergency communications] in attempt to be able to communicate better with the aircraft. We cannot cross-couple at this sector because the western frequency is not usable on the far east side; and we don't like to use 135.72 as an alternate in case we don't switch them early enough and thus lose the aircraft.additionally; rides had begun to deteriorate and I needed to get all aircraft at FL280 or below (I own from FL240-FL330) or up above FL340. There was a lot of changing altitudes occurring at this time. The sector beneath me (windsor/dresden) was helping me out by climbing aircraft from below and missing my traffic while I attempted to resolve the frequencies after I had reported issues to my supervisor.I switched an aircraft - aircraft Y - to the next sector (rav) right on the boundary after a call for them to accept the handoff. There was interference on the frequency during the response; but upon reviewing the tapes apparently aircraft X took the switch for aircraft Y. I did not hear it; and had not made the aircraft aware of similar sounding call signs ahead of time. The next sector must have missed the incorrect call sign. They descended aircraft Y (who was not on their frequency yet; though we didn't know it) from FL260 to FL240. The sector below me had climbed aircraft Z to FL250 beneath aircraft X with my approval. We saw FL257 in the datablock. I immediately told aircraft X to maintain FL260 for traffic with no response. I called again. I attempted to reach aircraft X several times on frequency with no response.in the meantime; the sector below me stopped the climb of aircraft Z and turned him 30 degrees left with my approval. I called a safety alert to aircraft X and told him to turn left and climb if he could hear me. Aircraft Z responded to a TCAS RA.the controller at the sector below me and I were operating under the assumption that aircraft X was experiencing an emergency and expedited the descent of another aircraft that might have been a problem in the future.I received a call after the traffic was no longer a factor from the sector that had aircraft X on their frequency to tell me that he'd taken the switch for aircraft Y. Until that point; I had no idea that there'd been a readback error.better working frequencies; better communication with foreign aircraft and an attempt by airlines to not have such similar sounding call signs on such similar routes at such similar times. (This is a frequent problem for us with ggn) it would have also helped if either I or the controller at the rav sector had heard the mistaken call sign of aircraft X instead of aircraft Y.

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Original NASA ASRS Text

Title: Cleveland Center controllers reported radio problems along with similar sounding call signs led to and unsafe situation.

Narrative: I was working a combined sector at HUD/DET. I had reports from ZAU that aircraft couldn't hear me/I couldn't hear them; so I was moving from Mains to Standby then finally to BUEC [Back Up Emergency Communications] in attempt to be able to communicate better with the aircraft. We cannot cross-couple at this sector because the western frequency is not usable on the far east side; and we don't like to use 135.72 as an alternate in case we don't switch them early enough and thus lose the aircraft.Additionally; rides had begun to deteriorate and I needed to get all aircraft at FL280 or below (I own from FL240-FL330) or up above FL340. There was a lot of changing altitudes occurring at this time. The sector beneath me (WINDSOR/DRESDEN) was helping me out by climbing aircraft from below and missing my traffic while I attempted to resolve the frequencies after I had reported issues to my supervisor.I switched an aircraft - Aircraft Y - to the next sector (RAV) right on the boundary after a call for them to accept the handoff. There was interference on the frequency during the response; but upon reviewing the tapes apparently Aircraft X took the switch for Aircraft Y. I did not hear it; and had not made the aircraft aware of similar sounding call signs ahead of time. The next sector must have missed the incorrect call sign. They descended Aircraft Y (who was not on their frequency yet; though we didn't know it) from FL260 to FL240. The sector below me had climbed Aircraft Z to FL250 beneath Aircraft X with my approval. We saw FL257 in the datablock. I immediately told Aircraft X to maintain FL260 for traffic with no response. I called again. I attempted to reach Aircraft X several times on frequency with no response.In the meantime; the sector below me stopped the climb of Aircraft Z and turned him 30 degrees left with my approval. I called a safety alert to Aircraft X and told him to turn left and climb if he could hear me. Aircraft Z responded to a TCAS RA.The controller at the sector below me and I were operating under the assumption that Aircraft X was experiencing an emergency and expedited the descent of another aircraft that might have been a problem in the future.I received a call after the traffic was no longer a factor from the sector that had Aircraft X on their frequency to tell me that he'd taken the switch for Aircraft Y. Until that point; I had no idea that there'd been a readback error.Better working frequencies; better communication with foreign aircraft and an attempt by airlines to not have such similar sounding call signs on such similar routes at such similar times. (This is a frequent problem for us with GGN) It would have also helped if either I or the controller at the RAV sector had heard the mistaken call sign of Aircraft X instead of Aircraft Y.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.