Among other things, it pushes traffic from commercial corridors (where noise is expected) onto residential ones. Then you get people leaning on their horns right outside your window all evening when you're trying to concentrate on work or are exhausted and just want to sleep - because the way the lights are timed on the side streets means that not everyone makes it through the light (or when the traffic on the arteries is heavy, nobody on the side street makes it through the light).