Ok, this is kinda strange. A couple times while under my car, I'll hear a really quiet squeal / buzz noise coming from somewhere in my car. It's happened even with the battery unplugged. It lasts for five seconds and then stops, and then may occur several minutes later. I can't tell if the noise is electrical, or possibly pneumatic. Has anyone heard such a thing even with the battery unplugged?

 

Well since it does it even with the battery unplugged I would just about rule out electrical. Ive never heard of anything quite like that but I could only suggest having someone stand outside the car to see if they can pinpoint where its coming from, sounds like it could just be settling or something?