If external stimulus is applied to the brain, it becomes possible to entrain the brain frequency from one brain state to another. For example, if a person is in the beta state (highly alert) and a stimulus of 10Hz is applied to his/her brain for some time, the brain frequency is likely to change towards the applied stimulus.
The effect will be relaxing to the person. This phenomenon is also called frequency following response or Brainwave Entrainment.
When the brain's state is close to the applied stimulus, entrainment works more efficiently. Thus, when doing a sweep from one frequency to another, the starting frequency should be as close to the current brain state as possible. The sweep speed should be such that the brain's state changes steadily with it, so that the difference never gets very large. In practice, it is difficult to determine the brain state without complex EEG measurement equipment. However, you can quite safely assume that during the day your brain is in the beta state (about 20Hz) and you can start a frequency sweep from there. If you are already somewhat relaxed, you can use a start frequency of 15Hz or a few Hz lower.
Stimulating the brain
The easiest way of applying stimulus to the brain is via ears or eyes. Since humans cannot hear sounds low enough to be useful for brain stimulation, special techniques must be used. One such special technique used is called binaural beats.
If the left ear is presented with a steady tone of 455Hz and the right ear a steady tone of 445Hz, these two tones combine in the brain. The difference, 10Hz, is perceived by the brain and is a very effective stimulus for brainwave entrainment. This 10Hz is formed entirely by the brain. This phenomenon is called the Phantom sound. When using stereo headphones, the left and right sounds do not mix together until in your brain. The frequency difference, when perceived by brain this way, is called a binaural beat.
To get a stimulus of 10Hz, you may use tones of 495Hz and 505Hz, or 400Hz and 410Hz, or 862Hz and 872Hz, or so on. The only requirements are that the tone is heard well enough and that it is below about 1000Hz. Below 1000Hz.
Stimulating the brain with visual stimulus
Visual stimulation is easier than aural stimulation because low frequencies can readily be used. A frequency of 10Hz, for example, is generated when a led is flashed on and off 10 times a second in the front of your eyes.
When visual stimulus is in synch with aural stimulus, effects are highly increased over using only visual or only aural stimulus.
Brain States and Frequencies
Entraining the Brain to Desired Brain State
Effects and Applications of Brain Entrainment
How to Use Brain Wave Podcast
Brain Wave States
Entraining the Alpha Waves Brain State
How to Meditate? - 5 Golden Rules Of Meditation
Intuition: The Sixth Sense
Awakening the Life Force Energy