Binaural beats are based upon what is known as “beats”, “subjective tones”, or “difference tones” (different names for the same thing). All of these are basically just the difference between two frequencies. When two sounds are mixed in the air, the differences between the two “tones” causes constructive and destructive interference which produces another tone, known as the primary beat frequency. Mathematically it’s Fb = |f2 – f1|. So, if you want to generate a specific beat frequency, it’s pretty easy to calculate using the equation.For example, a 50Hz tone with a 60Hz tone will generate the difference tone of 10Hz (60-50).
Anyone who has tuned an instrument has probably encountered this beating effect. Many people use this effect to their advantage while tuning a guitar. Fret the same note on two different strings, and then play both notes simultaneously. As you tune one string closer in frequency to the other, you will hear the beat frequency oscillate slower and slower as the two tones get closer together. When they are the same, the oscillation stops (there is no difference). This is a great tool for tuning, as you can just listen for the beating to stop. You can try this on any instrument capable of variable tuning to hear the beating effect for yourself.
Binaural beats are a more specific application of frequency beating. Instead of mixing the two tones together in the air to generate the difference tone; the tones are individually fed into your left and right ear using headphones. As an example; your left ear is fed a 50Hz tone, and your right ear is fed a 60Hz tone. When mixed in the air you would expect a 10Hz difference tone due to the interference. However, since we are feeding the tone to each ear using headphones; the interference is minimized. Despite this, we still get a 10Hz subjective tone created in your brain or auditory system. How exactly this is accomplished is an area of controversy.
One subtle but important point about this process is that it allows you to generate very low frequency beats quite easily (i.e. less than 20 Hz). In most cases these frequencies are out of range for most sound reproduction systems. So, this allows generating very low frequencies, using standard sound reproduction equipment. This is important because the commonly known brain states operate in these low frequency ranges (i.e. alpha, theta, delta, beta).
If we take binaural beats and use them to elicit a “frequency following response” effect; we can potentially get the brain will follow along at or near a desired frequency. The “frequency following response“, is basically the idea that when fed a specific frequency stimulus; your brain will tend to follow along or match the stimulating frequency. So, if you feed a 10Hzdifference tone as in the examples, it will attempt to follow along at 10 Hz (alpha state).
The overall idea is to get your brain to follow along at a specific frequency range to achieve a certain state. If you pick the appropriate frequency range, you can target certain well known brain states; such as the Alpha, Beta, Delta, and Theta states.
- Delta is 0-4 Hz and is associated with sleep.
- Theta is 4-8Hz and is associated with meditation.
- Alpha is 8-14Hz and is associated with relaxation.
- Beta is 14-30Hz and is associated with alertness.
Binaural beats can be useful for certain audio programs, where you want to encourage your brain into a specific brain state. There are many “states” claimed; but please understand that in most cases this information is fairly subjective and personal. You should keep in mind that everyone is different and may have a different experience. You will need to relax, and be receptive to the process; generally improving the more you do it.
The advantage of binaural beats is that they are fairly easy to create and encode directly into existing audio material, and require no special hardware. This can be really useful for hypnosis CDs, where we can try to get the user into a more receptive state during the Hypnosis session.
Binaural beats are not the only way to elicit the frequency following response. You can also use light stimulation. In this technique you wear a pair of goggles which flash at the intended frequency. In most cases these devices also generate binaural beats, synchronized with the light (check out the Orion and Proteus). These devices contain various built in programs that control the flashing, modulation, and colors of the light and sound for a powerful combination.