It's funny how conditioned we can become. There was a five year period in my life that I lived aboard ships while in the Coast Guard. When underway, the drone of the diesels and the rocking of the ship would lull me to sleepy time. But whenever we would hit port, the quiet of no engines running and the lack of tossing about would keep me awake.
I grew up next to a river with a dam just down the banking from our house, the sound of that water pouring over the dam was a constant, but we were so used to it that we tuned it out. Whenever I would sleep somewhere else back then, I couldn't sleep because of the lack of that water caused white noise.
During my thirties, I was living in a condo with a highway that ran by on top of a steep embankment across from us. The sound of the tires from the cars and trucks rolling by became a calming backdrop at night when all of the other normal people sounds diminished for the evening hours, the melody of those tires approaching and then receding became a calming sound to drift off to.
Presently I am surrounded by farms and woods, while being in a developed rural neighborhood, we are at the edge of it. I hear crickets and tree frogs, bull frogs and coyotes at night now, with the baying of cattle and the call of barn owls, along with the other various squawks, talks and screams of other species of wildlife. Summer is the best as all of the critters are making their own particular songs be heard at night, it's never quiet.
I still miss, after all these years, the simple sound of that water cascading over the dam, an endless calming white noise...