Dead Quiet! If its not Quiet, I'll make it Dead! and quiet.
I grew up, and lived in the big city most of my life. I did not always have a choice of my sleeping conditions, cept whom I slept with. Sirens, helicopters, traffic, semi trucks, ect. I don't miss it one bit!
Now, I have to sleep with my windows shut because the coyote's howl, the deer and elk grunt and stomp at the coyote's, and it bothers my dogs and both of my cats, and it messes up my whole peaceful sleep thing I have going!
For those of you that use fans all night, it blows dust, and or other airborne particles for you to inhale all night long. It is said to be bad for your respiratory system and after long term exposer may develop respiratory issues. I already have them from childhood without exposer to dust or particles. There are these things called dust mites also.
T.V. Also Bad, many studies have shown it disrupts sleep patterns, and even with your eyes closed you still are visually stimulated by the flashing light because the TV is on while the room is dark. My 77 y.o. mother's TV pretty much has "Never" been turned off in 20 years! Her sleep patterns have been completely wacked the whole time, but what do I know? I'm her son, IDK ****!
I sleep in pitch black, with No fan of coarse!