Meanwhile, Hong Kong and Tokyo have higher population density, and they're not as noisy. These cities have 2 things in common: first, they have top notch public transportation (especially HK. If you have tried the MTR, Elon Musk's past jabs at public transportation ring hollow: clearly he doesn't know), which means much reduced traffic -- it's still busy mind you, but "European capital" level of busy. And second, they have (or have learnt) that most essential of things in urban life: etiquette. They know when to shut up. I will add that around 40% of Hong-Kongers are immigrants, mostly from (much more noisy & unruly) Mainland China, so clearly that etiquette thing is not innate and can be learnt.

So I would make the case that if you want a high-density city in the West to remain tolerable noise-wise, basic regulations are not enough. You need some 'investment', both in the local administration and in the local culture.