Oh man, we have three of our own cats, plus one foster, and we are getting more kittens to foster soon so I'm not looking forward to this sort of thing. Our foster is a prowler/growler but luckily with the bedroom door shut, we can't hear him when he gets going.

Maybe some earplugs? I use that usually during the feral cat mating season starts up. They seem to prefer right under my bedroom window.