Brainwave Entrainment
Brainwave entrainment is a way to achieve a state that it is difficult for you to reach on your own.
If you find it hard to relax for example, or to sleep, you can use brainwave entrainment to help you.
What Is Brainwave Entrainment? 
Brainwave entrainment is a way of changing the rhythm of the electrical pulses that your brain makes. The pulses are what is measured when a person has an EEG done on their brain.
These pulses are produced all the time and the rhythm varies throughout the day depending on what we are doing. If we are busy and alert the pulses are faster than when we are relaxed. When we close our eyes they are slower than when our eyes are open. At night when we are ready for sleep the pulses slow down even more.
It has been found that if certain sounds are played to us this can change the rhythm of the brain's pulses, or brain waves as we call them.
Why should we want to change the brainwaves? Because it has been discovered that the brain responds to the sounds by changing what it happening in the body. If you can slow the brain waves down it will cause your body to relax naturally and easily. All you have to do is to sit quietly with your eyes closed and listen.
There are audios that you can buy which will do this. These audios have the brain rhythm you are seeking embedded in them. Some of them have relaxing music as a background so you can't hear the pulsing too much. If you would like to try brainwave entrainment you can find some good ones here: Brainwave Entrainment Downloads
Resources For Brainwave Entrainment
Information about brainwave entrainment
Brain wave entrainment for sleep : Sleep Sound Insomnia Treatment