I have the ability to fall asleep almost any time, any place, in nearly any position (other than standing). One year in college, I lived in an apartment where my bedroom window faced a rail line that was probably only 75 feet away. There was a railway crossing about 100 yards down the line, so we not only got trains rumbling past many times a day, but the sounds of the crossing alarms, too. I think it took me less than a week to be able to sleep through all that.