What Causes a City to Be Noisy or Quiet?

Some cities are noisy and some are quiet because of the things that make noise. A city with lots of traffic, people talking, and machines working is loud. A city with fewer cars, more trees, and less activity feels quieter. Imagine a city like a big room, if you have a lot of people shouting in it, it's very noisy. But if only one person whispers, the whole room stays quiet.