I’m sitting here typing away, and I keep hearing some animal call outside. I’ve never heard it before. It’s not human. It’s a single long “Whoop!” and the pitch drops a bit towards the end, like
Whooooooooop.
I’m thinking “owl” but I’ve never heard one like that. As I was coding that sound effect, it stopped. Any ideas as to what it might be?
I didn’t hear it. You’re imagining things again. Just turn the music up a notch.
Sounds to me like you’ve got yourself a nasty case of Krikkit robots.
I’d recommend not answering the door.
Maybe its a dove? I have those all over around here, and at first I thought they were owls too.
Yuh, ah heared it too. If yuh lissen keerful, yuh’ll heer it bout ever nite.
Ah seen 'em. Jus barn owls.
I don’t think it’s a dove, it was night. And it wasn’t Krikkets as I’m not dead yet. Wasn’t a barn owl. I did some searching and I guess it may have been a great horned owl, which I have heard around here before. But it wasn’t a classic call, either. If you go to this page, and click on the first audio file, it sounded like just ONE of those hoots. And longer. And higher pitched. So given those caveats I’m doubting that was it, but there doesn’t seem to be another owl species found in Michigan that sounds anything like it.
Maybe we have howler monkeys.
Warning: sound files are creepy and may cause you to glance over your shoulder nervously if you are surfing the internet with a flashlight from a tent in your backyard. 
Ever seen Pitch Black?
People. I think you should flee!!!
Wasn’t me. Although I just belched a moment ago.
Barn Owls make LOTS of different noises. Might actually be one, although I couldn’t tell you without actually hearing it. Nightjar, perhaps? Poor-will with a bad accent?