Cities aren't loud; motor vehicles are. Tire noise near heavy stroads and highways are in particular egregious offenders. There's a lot of other points in the comments about some other urban nuisances (leaf blowers, anyone?) but I encourage anyone to walk around (yes, walk) while measuring the ambient noise levels with your smartphone's microphone.
It will be extremely obvious where the noise is coming from. This is an often misunderstood part of "the war on cars:" the stress gained from additional constant noise (e.g. like a highway) takes YEARS off our lives.
And don't get me started on how loud shops are in North America. For whatever reason they seem to always keep the volume three or four levels above comfortable, making it much harder to have a conversation without shouting at least a little.
It wasn't until I started traveling a lot that I started to notice any of this. You can have your quiet part of town, but often you get to your quiet part of town by driving through the noisiest part of town where a good number of people live and work.