The El

In Chicago, the trains operate underground, at street level, and some are elevated. The latter are called "el" trains, or simply "the el". In the downtown area, they are very loud as they blast past you overhead with the noise ricocheting off of the tall buildings they ride between.

I don't remember which book it was, but Kurt Vonnegut described the sound of fighter jets taking off from the air base near where his character lived as a sound that "ripped the sky to shreds". I am often reminded of his words when I hear the el.