I only notice when I visit my parents. It's super quiet there and I often sleep for 10 hours or more. I never sleep that much at home with air condition noise from the neighbors and cars driving by. Sometimes when there is a power outage you suddenly notice how quite it can get without all the background noise.
As someone who must have been a guard dog in a previous life, I can sleep absolutely fine in the middle of a busy city or next to a busy road or near an airport. But it's the noise variations that gets me. IE in residential areas outside the city it's usually very quiet at night, except when it's suddenly not. In the cities its always pretty loud so there's little sudden change of noise.