Can you say a little bit more about this? What's the difference in how the cities are structured that makes this so?

Very strong mass transit systems, so there are fewer cars on the road.

The cars that are on the road tend to be quite new, which is a result of a stringent mandatory inspection after a car gets older that makes it more economical to export the car and buy a new one. So cars are typically in excellent repair, with a small economical engine. The driving culture is generally conservative. People don't race each other, compete for the loudest exhaust, roll coal, etc.

The cities are much more walkable as well. It was mind-blowing to use Google Maps for walking and transit door to door including specific numbered staircases for train stations with precise to the minute schedules for the trains.

I think partially they just care more. I remember when I visited Tokyo on a trip and would always see a decibel monitor on construction sites. I believe there was also a sign indicating the acceptable level of noise based on the time of day.