I remember I used to listen to all sorts of music, but recently, Just absolute darkness gets me going. I usually sleep when I feel sleepy so I dont have a problem trying to sleep
i always had something electronical that would blink with blue lights in complete darkness, and if i go to sleep without these lights i get nervous and cant sleep
In pure darkness. My bedroom is treated so it's absolutely pitch-black. Not even a dim LED from charging ports, the night sky through the edge of the curtain, or anything.
But I can't really fall asleep with an eye mask, so traveling is always a bit of an issue when there's even a tiny bit of light in the hotel room.
I stare at the ceiling in pure darkness for 4 hours thinking about every single interaction I had in my life until my body shutdowns - or doesn't and I'll get to try it again next day.
Other than the faint light from my PC tower, I sleep in the dark usually. Depending on how tired I am I can KO even if it is bright. Hard to sleep with loud noises for me, though I do on and off listen to a variety of things in order to fall asleep (ASMR, music, etc.)