I don't need to hear automobiles, sirens and jackhammers when they are really far away. These things change the mood of a place, like ruining the atmosphere of a book by listening to music. In the city, sounds make me feel like I'm living in a small box with a lot of disrespectful people.
like to look at the buildings, though, so I want clear soundproof barriers, like tempered glass walls on steel frames. At its cheapest, you build a few walled regions around the city for pockets of quiet.
More expensively, you put up seven-foot barriers at every sidewalk corner. Of course crossing the street now requires an overpass, such as the Monkey Bar Pedestrian Overpass.
For maximum efficacy, build these partitions as tall as buildings, between buildings, using gates for cars in blocks. The gates automatically close at a red light and reopen otherwise. Such a comprehensive system would baffle the troublesome high winds between buildings. The glass also may prevent some injuries by stopping some projectiles.
Your city may become a bankrupt greenhouse employing 30% of the world's window cleaners. The City Soundproofing System burden may drive residents away and ruin tourism. The benefit of this mass exodus is, of course, that the city will become even quieter.