We're talking about densification. In a non-dense (e.g. American) city, everything is spread out, there's highways, so cars travel very fast. In a dense city

We're talking about densification. In a non-dense (e.g. American) city, everything is spread out, there's highways, so cars travel very fast. In a dense city like Copenhagen (and also here in Tokyo), there aren't many highways or cars so the traffic is mostly trucks traveling at low speeds. Tire noise is negligible at very low speeds, but diesel engines are noisy. So in a dense city, you notice the noisy trucks with their clacking engines. In an American city, vehicles are whizzing by at 100+kph on multi-lane roads or highways, so you hear tire noise, even from a distance. Making all the cars in America electric isn't going to do anything about highway noise. But making all the trucks in Tokyo electric would really make the roads here a lot quieter (and they're already pretty quiet, it just depends on where you go; places with lots of stores need trucks, whereas neighborhoods don't).