I only see them when it's noisy.
The first time I saw one, I was walking back to my hotel from a train station in Chicago. They have the big, suspended-in-midair trains – I guess the locals all call it the El – that make this incredible sound when they go by overhead, and for a minute or two as it passes you can't hear anything except this enormous racket. It's a whole body kind of sound, and you can even feel the sidewalk vibrate under your feet when it goes by.
Anyway, this train is coming by above me, which I'm not used to. The Chicago natives seem totally unperturbed, but me and a couple of other tourists all look up to gawk at it. I look down after a couple seconds, and that's when I notice him staring at me. Well, staring, I guess. I don't know the verb for when something is looking at you without eyes.