Before i got on meds that take the voices away i used to try a quieting meditation. I would focus on the voices with my mind, and my attention and 'will' them to be quieter. I could imagine that they were getting quieter and quieter, and imagine that they are being pulled away from my mind. The mind is really a powerful tool, and since they are in your mind you can use your mind to move them, and to control them. I used to make commands onto them too, like i would say affirmations like 'when i sleep the voices get quiet.' If all else fails you can put on some headphones and listen to music until you sleep. You could also negotiate with them, and talk to them, ask them to be quiet and respectful. Some of my meanest voices actually responded well to me being nice to them. i converted some into friends.

best wishes...