Air draft / sound--air conditioner?

Does the window face into an air shaft or or other narrow space? That can sometimes cause a wind-tunnel effect that produces wind noise. It could also be your window seals--if they aren't tight you can get whistling, etc.

Thanks Bramstar. Window faces the street ... that is just a block from the Hudson river. Windy. Short of having the air conditioner removed during winter, I can't seem to find a good solution. I should try insulating tape, maybe?

Ah yes--the Hudson. I live on RSD and also have that crazy wind. You could certainly try some kind of insulating material (or perhaps one of those AC covers). But again, it could also be your window itself. Before we replaced our windows we'd get that tundra-like howling going on in the winter months. There may be ways to have your windows sealed without going to the extreme of replacing.

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if you AC producing any sings from these points you need professional help.
Thanks and regards
James Allison