I don't know what it is, but we heard it down by lake Michigan in Chicago in late August. There are many train tracks there and I could only assume it was heavy machinery slowing via friction brakes. I have heard trains braking and they did not really sound like that though.
I don't know what it is, but we heard it down by lake Michigan in Chicago in late August. There are many train tracks there and I could only assume it was heavy machinery slowing via friction brakes. I have heard trains braking and they did not really sound like that though.