Anyone familiar with an EEG knows that when a brain is active (and unless you are dead, it is) there are measurable oscillation frequencies, known as brainwaves. In short, different frequencies correspond to different states. For example, beta waves correspond to the normal waking state when we are active doing something or concentrating on something. For those who wish to enter a state between dreaming and waking, the goal is to have brainwaves with a theta frequency. This “twilight” frequency is the frequency at which people have lucid dreams or can enter while still awake under deep meditation. However, not all of us are lucid dreamers or able to meditate so profoundly without falling into a deep sleep. Enter brainwave entrainment.
The whole concept of brainwave entrainment is that the brain’s neural oscillating frequency is brought in line with a desired frequency. This can be done in a number of ways, whether aural, visual, or both. Let’s take a closer look at each method. First, we’ll look at aural brainwave entrainment.
Aural brainwave entrainment seeks to alter one’s brain state through the use of audio. There are four common methods used to achieve this – binaural beats, monaural beats, isochronic tones, and through music modulation and audio filtering.
Binaural beats, discovered by German scientist Heinrich Wilhelm Dove in 1839, but not popularized until the late 20th century, involve using two audio output methods (such as two speakers) at different, but close frequencies to produce a steady rhythmic beat. The way this works is simple. Let’s say we have two speakers – one for the left ear and one for the right. If we have the left speaker produce a frequency of 350 Hz and the right speaker produce a frequency of 355 Hz, then the brain will compensate for the difference and the listener will hear a beat with a frequency of 5 Hz. Note that the person does not actually “hear” the beat, per se – it is an effect produced by the brain in the cortical areas (much the same way as the brain makes up for blind spots). You can play with an online binaural beats generator to entrain your brain right now.
Monaural beats are like binaural beats in that they involve using two sounds at close, but different frequencies to produce a beat with a frequency equal to the difference of the two beats. The similarity, however, stops there. With monaural beats, only one audio output method is used. Also, the beat is actually heard as it stimulates the basilar membrane of the inner ear as opposed to being “made up” by the brain as with binaural beats.
Isochronic tones involve producing a beat by repeatedly turning on then switching off a tone in rapid succession. The effect is, as with binaural beats and monaural beats, to produce an altered brain state than one originally started with.
The fourth form of aural brainwave entrainment that we’ll discuss here is through music modulation and audio filtering. The way this works is to modulate the frequency of a song or other piece of music (it can be anything from heavy metal to classical). Since this can cause distortion of the audio, it is possible to modulate along particular frequency bands. The brainwave entrainment (ex. binaural beats) is embedded at a low frequency, leaving just the bass portion of the song affected and the rest unaffected. Thus, listening to one’s favorite songs under this method can lead to alteration in brainwave frequency.
The goal of visual brainwave entrainment is the same as with aural entrainment, namely to induce an altered brain state. However, the method – as the name suggests – is to stimulate the brain through vision, rather than sound. As with aural brainwave entrainment, there are a few methods for doing this, but we’ll just explore one here – AVE (audio visual entrainment). This type of entrainment may use pulses of sound with a pulsating light (hence the “audio” portion) but does not need to. Quite often, though, visual entrainment is used alongside aural entrainment, so that a person sees a light flash in time with the beat of, for example, a binaural beat.
It is important to close with a sort of “caveat emptor.” While brainwave entrainment can be useful for entering a desired brain state almost effortlessly, it is not without its drawbacks. People with a history of seizures should not use brainwave entrainment, as it could trigger another seizure. If, during a session, any negative feelings (nausea, dizziness, headaches, etc.) occur, one should stop the session right away and not try again. Other than that, brainwave entrainment is a great way to relax and enter realms you may not have otherwise been able to reach.