Darkness can be an incredibly good technique at prolonging their sleep cycle or reducing the stimulus of their surrounding environment. By simply covering their sleeping quarters you can buy yourself an extra 30 minutes of sleep by delaying their loud squawking in the early hours of the morning. You will really need to create a pitch black coop or sleeping environment. Another possibility is to individually place them in a cage in order to reduce the stimulation of the rest of the flock. I don’t recommend doing this for longer than 30 to 60 minutes as that would just be unfair to your bird, egg layer or not. This is by far the most effective intervention regarding darkness, but it is also the most questionable in terms of ethics. This technique also requires that you get out of bed chase down a loud hen and put her against her will into a smaller cage in a remote sound proof part of your house, barn, or garage. This kind of sensory deprivation, fortunate for you, unfortunate for her, will have a large effect on the hens noise making.