I use the aid of one of
these to sleep if my mind is overactive when I want to sleep.The lights and bin-aural beats entrain your brain waves, and a 15 minute `Sleep' program entrains your dominant frequency of electrical brain waves effortlessly down into the Delta ( <4Hz) region.
Works for me 100% of the time. Slow ambient music or repetative natural sounds can have the same effect. A $200 amateur built electroencephalogram (EEG) is capable of showing how well they work. I sometimes use Beta frequency programs which enhance the mind activity in the 13 to 30Hz region , before I want to tackle challenging technical reading. Its cheaper and far less physically taxing than coffee
Brainwave entrainment has been going on since we were lived in caves. The flickering frequency of a warm fire easily puts us into the Alpha range ( 8-12Hz ) where we are more susceptable to soothing feelings and vivid visualisation in a dream like state.