I love the sound of trains. The Marunouchi line, an electric subway, makes a brief above ground appearance near our new apartment. Every few minutes, I hear the muted roar of trains going by. I haven't yet learned to distinguish their direction, but I will. And I suspect that I'll be able to tell what time of day it is by their frequency.

They're passing every two minutes right now--I'd have to say this is rush hour.