By By Paul Cage, U.S. Naval Research Laboratory Corporate Communications WASHINGTON, – Imagine living in a large city. New York City, Los Angeles, or Washington. One morning you hear a siren off in the distance. You know the direction and that it was far away since it was just loud enough to hear. You wonder if it’s an emergency. What type of siren was it? Police, Fire, EMS? But you never hear it again. Time passes, then one night you hear another siren, then another, eventually hearing sirens all the time. So what does this have to do with ...