Might seem odd, but I found a YouTube video that seems to put me out rather quickly. It's 10 hours of a black screen, but a light thunderstorm and campfire noises. I put this on and I'm asleep in short notice. Be careful though, there is an 'alarm' at the 10 hour point, which is a wolf howling. I made the mistake of playing the video at the point where it left off the previous night. When it reached 10 hours, I woke up wondering what the hell was making that noise! Pro tip, restart the video from the beginning or at least far back enough where you won't hit the 10 hour mark.