They are extremely loud, second only to no muffler cars and sport bikes blasting through deserted back roads.
If you live in the woods with trees, they'll sound as loud as the ocean. If you live near the ocean, well that's always loud.
The biggest offenders are:
1. cars/trucks 2. birds 3. airplanes 4. ac units 5. ocean 6. wind with trees
You'd never know trees sound like the ocean if you aren't around trees. Trains are loud but intermittent. And trains don't run very often anymore where I am.
GP is very right. To this day, I know that if I don't go to sleep until ~03:30, I might just as well stay up - when the birds wake and start making noise, I won't be able to sleep at all. Cars, trams, trains, I can tune out. There's something about bird chirps that makes them impossible for my brain to ignore. It's worse than loud snoring.
Unrelated. To the noise but just as obnoxious, They also seem to get a pervasive joy in cutting town in half by parking their trains in the main line running through the middle of the town lengthwise. I understand the rail line was here first and the town grew up along the length of the track, but why they cant park their train on the miles of empty straight track outside of town. It boggles my mind.
It's easy from a technical standpoint but practically impossible from a human one. The vast majority of people simply don't notice or care that some large percentage of vehicles are intentionally modified to be louder than the legal maximum. Police won't enforce it, and most citizens barely register the noise as present, much less a problem.
Banning ICE vehicles altogether may very well be the only thing that actually gets the problem solved, since that actually has more momentum behind it than enforcement of existing noise regulations does.
If 5% of those are overly loud, that's an average of a very loud noise every 3 seconds, and most of them will take somewhere between 5 and 10 seconds to come and finally go away. If you don't think that's large, we have very different noise thresholds.
The hard numbers I'm aware of are about motorcycles, which have much higher rates of illegal modifications than other vehicles. This source documents a bunch of other sources, with estimates ranging from 40-70%:
When Harley-Davidson and other moppet/scooters would be all electric, that would be quitter.
Not that easy, the electric Harley is intentionally louder than the combustion version - because people want them loud.
(I am not a fan of banning in general, but banning noise is fine by me)
You cannot even hear modern ICE cars running unless you are really close to them. My neighbor's garage door opener is louder than his ICE car...
Road noise is tires/air like you mentioned. Not a real way to deal with that.