I like to think about the time around 1900 when the population was far far higher than today, but there were no cars. Horses don’t make the same noise.
Of course there was heavy industry in that day so that would be loud and filthy.
How quiet was dense NYC in 1830 though?
I guess it would depend on where you were. If you're in a high traffic area full of horses wearing metal shoes stepping on cobble stones and handcarts with metal rims rolling over cobble stones, it could probably get pretty loud.
I bet it could get pretty quiet, even with the density.
College campuses are often pretty dense but also pretty quiet.