Is entrainment the whole story?

When looking at all the promotional material for audio-visual stimulation products you could be forgiven for gaining the impression that brainwave entrainment is the best thing since sesame bagels. Unfortunately ‘entrainment’ has become a catchword that has come unstuck from its actual meaning.

When the brain receives a pulse of sound via the ears, there is an evoked potential visible by EEG in the region of the auditory cortex (temporal region). If this pulse is repeated at a consistent frequency the EEG will show a frequency following response (FFR) in the same region. Under certain circumstances, the conditions for which are unclear, other regions of the brain may fall into lockstep with the auditory cortex and a signal corresponding to the stimulus frequency may be seen in other areas of the cortex. When other areas start following the initial stimulus, then we have the phenomenon correctly referred to as entrainment.

Exactly the same sequence of occurs with visual stimulation in the form of flashes of light. First there’s the evoked response in the visual cortex and secondary visual areas, then there’s entrainment if areas of the brain not generally associated with vision start following.

Activation of the brain’s non-visual and non-auditory regions by a repetitive audio or visual stimulus may occur at the same frequency, which may be considered true entrainment, or it may occur at multiples of the stimulus rate, or entirely different frequencies.

Auditory entrainment is beset by a number of difficulties.

Firstly, the brain responds to any significant stimulus with an evoked potential. This means that anything in addition to the stimulus, such as background music or environmental sounds, has the potential to interfere with entrainment. As a general rule, the most entraining sound is a simple train of clearly audible pulses. Such a train of pulses is often referred to as an isochronic beat – bursts of tone at identical intervals. Isochronic beats consist of a carrier frequency (pitch) and a beat frequency (rate). In the simplest form, the carrier is turned on and off at the beat rate. Fancier forms use a shaped wave to modulate the carrier. Modulating the carrier with a sine wave has two major benefits over simple square wave switching – first, it sounds more pleasant, and second, it minimises harmonics which can result in the brain responding at multiples of the stimulus frequency.

Next, we have aesthetics. More often than not, people find the insistent isochronic beat unpleasant to listen to. This is dealt with by adding background sounds, such as noise or music, and reducing the relative volume of the beats. The result is reduced likelihood of entrainment. The other alternative is to use monaural or binaural beats.

Monaural beats are the result of simple mixing of two tones. A tone of 100Hz combined with one of 110Hz will result in a plainly audible 10Hz beat. Monaural beats are less effective than isochronics, but they do work, and they are gentler on the ears.

Binaural beats make use of an idiosyncrasy of the brain whereby two slightly different tones presented to each ear create a beat. In this case the 100Hz would be applied to the left ear only, and the 110Hz tone to the right ear only. Most people, though not all, will hear a 10Hz beat originating within their head. There are a few explanations for this, the most popular being that it arises from the olivary nucleus where the brain tries to establish positional information from the phase relationship of the sounds arriving at each ear. A less popular explanation, one more readily demonstrated by experimentation, is that the binaural beat is the same as a monaural beat, except that the mixing occurs in the medium of brainstuff.

Binaural beats are the mainstay of entrainment mass marketing. A large proportion of the products that are accompanied by the most hype are based on binaural beats. The sad, bad news is that binaural beats do not entrain. Several researchers (Siever: Entraining Tones and Binaural Beats) have demonstrated that binaurals do not entrain. My own tests with an EEG don’t even show evoked response over the temporal region. This does not mean that sessions based on binaural beats don’t work, they just don’t work the way the promotional material says they do.

The final problem with entrainment is that it mostly doesn’t happen and it’s not obvious whether it matters if it does or not. Photic stimulation with light glasses has the highest likelihood of causing measurable responses in non-visual parts of the brain. Adding audio does not significantly increase the response. Audio on its own, and isochronic beats in particular, can entrain, but its effects are much weaker than photic stimulus. When entrainment does happen, there’s no direct relationship between a stimulus frequency and a particular outcome.

Entrainment occurs quite readily at 10Hz or thereabouts, which is the dominant resting frequency for most people. An EEG will almost invariably show a sharp increase in alpha activity at around 10Hz when an individual closes their eyes and relaxes. There is also a distinct burst of alpha associated with each blink of the eyes (blink response). Entrainment to any other frequency is both less in amplitude and likelihood. Below 2Hz entrainment becomes extremely unlikely – I have not seen it on an EEG and others have made the same observation.

So why, if entrainment is so unpredictable, are brainwave entrainment devices and software selling like hotcakes and accompanied by endless testimonials claiming effectiveness across a vast range of applications? Well, the answer is simple – audio-visual stimulation works. How it works is not obvious, but it does work.

There are a number of approaches.

One is the emulation of a known good brainwave pattern, another is using a frequency that is associated with a particular mental state or known physiology.

In the first case EEG recordings are taken from individuals adept at the practise of a particular activity. Monks have been recorded whilst in deep mediation and have shown elevated theta and delta, leading to the idea that theta and delta are good for mediation. The same monks when meditating on compassion have shown elevated gamma, resulting in gamma being associated with ‘higher’ consciousness.

In the second case there are two branches.

One is the observation of abnormal brainstates. Depression, for example, shows reduced beta activity and stimulation with beta frequencies has been shown in numerous trials to be helpful. ADD/ADHD shows a similar lack of beta accompanied by excess theta, and again, beta stimulus has shown its worth.

The other is the observation that certain neurotransmitters are released or particular structures within the brain are activated when particular frequencies dominate. Alpha frequencies are associated with serotonin release. The hypothalamus seems particularly responsive to sub-delta frequencies, leading to reductions in chronic pain.

Much of the information relating to this case has been extrapolated from successful research with neurofeedback. In neurofeedback the brainwave activity is monitored in real time and the subject performs exercises to cause changes to the dominant frequency. The validity of such extrapolation to passive AVS use is uncertain.

The third approach is the most useful for those who wish to design their own sessions. Each of the four major brainwave bands is naturally associated with distinct states – beta is alert and engaged, alpha is detached and relaxed, theta is dreamy, delta is asleep or deeply meditative. Knowing this, a frequency in the band associated with the desired activity can be chosen. There are no ‘magic’ frequencies and each individual will respond differently. Pick a frequency and try it out, using your mind to do the types of things associated with that frequency band, fine tuning as necessary.

Lot’s of people pick up an AVS device or CD with the expectation of a quick fix. Mostly it won’t happen. Some protocols (notably anxiety reduction) do seem to work first time every time, but most are progressive. Popular wishes, such as increased IQ or overcoming procrastination, are rarely fulfilled by passive use of AVS – the best way to increase your IQ is to use your brain, and the best way to overcome procrastination is to take action. The same applies to many applications – the AVS itself may or may not be directly beneficial, but it is always an excellent focus for creative visualisation and personal introspection.

To summarise…

AVS is a versatile tool for addressing a wide range of behavioural, psychological and physiological issues. Marketers have jumped the gun in offering specific explanations for its effectiveness. There are a limited number of applications where trials have shown a distinct correlation between AVS and positive outcomes, however the majority of supporting evidence is anecdotal or extrapolated from successes with neurofeedback.

At this point it would be easy to conclude that AVS is something of a scam. While there are some completely outlandish and unreasonable claims made, there are authentic positive results. Unlike many alternative therapies, such as homeopathy, where there is no active principle and no evidence whatsoever of physiological response, AVS does have clearly detectable effects on cortical activity. The causal relationship between this activity and the outcomes is unclear, but at least there is a set of mechanisms that may end up providing adequate explanation.

In my opinion, the greatest value to be derived from an AVS device is in taking a break from everything else and exercising the brain with pure thought. Having pleasing sounds and beautiful patterns of light blocking out the sights and sounds of the mundane world is a little piece of bliss accessible any time you have a spare half hour. The benefits of simple relaxation for the body, mind and soul should not be underestimated, and if this is all there is to explain the effectiveness of AVS, then it is enough.



  • jc  On July 19, 2009 at 3:01 pm

    Honest & direct seems to be your trade mark. Another great gold nugget in a nutshell!

  • Rob  On February 9, 2010 at 4:13 am

    Just wanted to say how refreshing it is to read an intelligent article about bwe. I get so tired of all the product hype. I am a fan. I use it all the time. It’s just all the Get Enlightened with Our Awesome Binaural Beat Product silliness that gets to me.

    • CraigT  On February 9, 2010 at 6:12 am

      Hi Rob,
      Thanks. Just doin’ my bit in a very small patch 🙂

  • yvonne  On February 13, 2010 at 8:01 pm

    my apartment building has very thin walls. my neighbor plays these pulsing tones (there are 2 or three different ones at different speeds) throughout the evening and in the day on weekends. this has been going on for about 3 months. it is driving me UP A WALL. i HATE that sound. i can’t stand it. it bores into my head and i feel like the only way to escape it is to fill my ears with sound (radio or cd player) but sometimes the tones go through THAT. at first i thought it was meditative bianural beats, but now i see that it’s “isochronic.”

    i complained to my landlord and she FINALLY turned it down this week. i can still hear it very faintly but at least i don’t feel like my brain is getting attacked.

    • CraigT  On February 14, 2010 at 9:07 am

      What a very peculiar thing to do. Are you sure it’s AVS content being played and not one of the various dance genres that feature driving beats?

      AVS has no requirement to be loud, and there is no benefit to constant, or extended exposure.

      I’m glad the nuisance has been abated.


  • jc  On May 9, 2010 at 8:34 am


    It would seem that spam has entered your blog-world!

    • CraigT  On May 9, 2010 at 9:32 am

      Not for long, and unusual. WordPress has a surprisingle competent spam filter, Akismet – this is only the third or fourth time a suspect post has not been held back. Hopefully it is not indicative of a deluge.

  • dkbrainard  On August 30, 2010 at 4:28 am

    Hey Craig,

    I appreciate the straightforward, concise writing about bwe claims and results. My experience as a bwe user for nearly a decade now is that it works. I’ve no measurable results to back that subjective knowing up (never used an EEG, etc.) – I just know that bwe products over the years have taught me that I can relax no matter how anxious or stressed i am. And the knowledge that I could, within 30 minutes at most, drop out of the monkey mind and into the alpha or theta level where my deep mind is always waiting to welcome me back to ‘ground’ has exponentially increased my fluidity and confidence in life.

    I guess we just have to keep finding what works, even if we don’t fully know why. Interestingly enough, I have found that the products of some of the companies who make the most grandiose claims for ‘instant enlightenment’ and the like are unlistenable to me.

    Thanks for the great writing – and in response to your review of Mind Workstation, I would LOVE to see an in-depth nuts and bolts review.


    • CraigT  On August 30, 2010 at 7:44 am

      It’s always great to hear from another who “gets it”. AVS/entrainment is an absolutely awesome tool once one grasps that “instant” anything rarely happens.

      As for in depth review of Mind Workstation – there’s little I can say beyond recommending that anyone who even thinks they may want to explore advanced stimulus should run, not walk, to their nearest internet connection and download the two-week free trial –


  • Thom L  On July 12, 2012 at 5:08 am

    Hi Craig, I stumbled across your blog yesterday while doing research on the Procyon AVS which i’m considering purchasing (OK, i’ve all but ordered the thing!). I too appreciated your straightforward no-nonsense take on BWE and AVS. I’ve been into BWE experimentation since i accidentally began creating Monaural Beats while working in my Electronic Music Studio in the late 1970’s with analog studio synths such as the Roland 700 and the effect on my mood.

    Then in ~2007 i found Transparent Corps products and began experimenting again with MWS and NP(now v3). This summer i will finally take the plunge and add the visual aspect of it all with the Procyon.

    Your comment that i quote here sums up my view of BWE/AVS well…

    “In my opinion, the greatest value to be derived from an AVS device is in taking a break from everything else and exercising the brain with pure thought. Having pleasing sounds and beautiful patterns of light blocking out the sights and sounds of the mundane world is a little piece of bliss accessible any time you have a spare half hour. The benefits of simple relaxation for the body, mind and soul should not be underestimated, and if this is all there is to explain the effectiveness of AVS, then it is enough.”


    • CraigT  On July 12, 2012 at 8:10 am

      Hi Thom,

      Pleased you’ve found my blog useful.

      You won’t be disappointed by the Procyon.


      • Sherry  On May 15, 2017 at 1:51 am

        SempticemenleMe scrive:voglio di nuovo David Tennant nel tardisssssss … lui si che è magnificooooo … IL MAGNIFICO DOTTORE E LUI!! .. deve essere bella questa serie… mi manki David

      •  On June 1, 2017 at 5:53 am

        Touch: Sinking in to a warm bubble bath at the end of the day and giant bear hugs! Taste: My farmer’s market quinoa salad with fresh garlic, cherry tomatoes, corn, basil and lemon.

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