Cities aren't loud, cars are. Unfortunately, if you live in the states, we've let cars overtake 99.9% of our cities. It's not this way everywhere.
I live in the city. It's loud af, but general traffic is only a small part of it. Essential services like police, ambulance, and fire sirens, and trash collection are massively loud. Then you've got bars blasting music on Fridays. People shouting, laughing, and, in general, existing (often till the wee hours of the morning). They there's the meth-fueled tweakers shouting obscenities. Construction noises. Road work. etc..
Density in general is loud.