Air carrier First Officer reported a loss of communication; static or interference; on 121.5 to the east of ZNY and from SAV flying north through DCA.

Narrative

Starting around Day 0; I have noticed that the guard frequency of 121.5 is not available in the northeast due to a blank carrier signal or possibly a continuously keyed microphone being held. This has gone on now for two weeks. This is problematic because ATC ground stations are not able to communicate with an aircraft on Guard when an aircraft is out of contact on the assigned frequency. I have noticed that the signal breaks squelch on our aircraft starting around Columbus; OH and gets stronger the closer you get to New York. I also heard the signal as far south as Savanah; GA while flying through Washington Center. There is no interference flying through the midwest. I reported the communications issue with New York ATC on Day 13 and they had no knowledge of the interference but would pass it on. After I reported it; a commercial aircraft concurred with my report to ATC stating they could hear the static or interference as well. The origin of this interference needs to be found and silenced so that Guard can be utilized again in the northeast.