Wow my cats are NOT happy about the new air conditioning unit. At first I thought it was because there were people in the apartment installing it, because they were both hiding under the bed when I got home. I fed them and they came out, but when the AC kicked on, they both skittered back under the bed. Even Nebula abandoned her food and she fears nothing. She wouldn’t even finish her food unless I stood next to her. I think it’s definitely the noise, because the only other thing Nebula fears is the vacuum, which I almost never use. Poor thing was shaking when I picked her up. 

I have it set pretty high so it won’t kick on often. The only thing I know to do is just let them get used to it.