It is pretty ambiguous.
I think most Americans would pronounce Noel as knoll/nole, which is understood to be the masculine version. No one has ever pronounced my name like Noelle (which is how I pronounce it), when they've just read it instead of heard it.
But Noel is pronounced as No-el all the time when it's used in relation to Christmas (like in songs). So I guess that carries over to names, but it's more unusual.
This message was edited 4/14/2018, 9:07 AM