Yes Rkttkmtj I think you are right. I finally got through to Frigidaire customer support and they told me this noise is a "feature" of this air conditioner. They didn't say why this is a "feature" but I agree that there is probably some kind of flap, possibly meant to limit venting between inside and outside air, that is making this noise. I've never seen this problem before and am now sorry I bought this Frigidaire as it seems there is nothing I can do about the noise.
Larry
March 2022
