Help identifying an animal sound?

Hi,

I need some help identifying an animal sound. Something keeps making a sound that sounds like a person who is trapped in a metal can groaning or gasping. I'll hear it in late spring and through late summer between late afternoon and after sunset. I have been trying to figure out what animal makes that sound for a year now. No one I've asked has any idea, but it is making me crazy. I hope someone on here can help identify this animal. The sound is short, harsh, and somewhat low pitched. I spend a lot of time outside, too, by the way. Thanks in advance. I don't have a recording though so my description should do.