Brainwaves, or neural oscillations, share the fundamental constituents with acoustic and optical waves, including frequency, amplitude and periodicity. Consequently, Huygens' discovery precipitated inquiry[citation needed] into whether or not the synchronous electrical activity of cortical neural ensembles might not only alter in response to external acoustic or optical stimuli but also entrain or synchronize their frequency to that of a specific stimulus.[16][17][18][19]
The objectives and inclusion criteria of the review were clear. Relevant sources were searched for studies, although the restriction to published studies in English meant that the review was prone to publication and language biases. The authors did not state whether steps were taken to minimise the risk of bias and error in the processes of study selection and data extraction (for example, by having more than one reviewer independently make decisions). The authors mentioned which studies were blinded, but it did not appear that study validity was systematically assessed, which made it difficult to judge the reliability of the review findings. The decision to combine studies by narrative synthesis appeared appropriate given the strong clinical heterogeneity between the studies, but the authors failed to quantify the size or statistical significance of the findings reported. The evidence presented appeared to justify the authors’ conclusions that further research was justified, but in view of the dearth of good-quality evidence and problems with methodology and reporting in the review, the conclusions regarding efficacy did not appear reliable.
Move-Thru-It Strategy: to support optimum recovery rates, use 6-8 pumps or 3-4 droppers. Repeat every 1-3 hours for a day or two (with a good night's sleep). The idea here is a persistent frequency. Once you have achieved initial results, you can switch to more conventional usage patterns such as 3-4 times a day. For example: Kick-Ass Immune, Get Over It
People who meditate regularly enjoy many benefits such as increased sense of well being, happiness, contentment, and far less anxiety that many other people. Some believe that this is due to both hemispheres of the brain being in sync with each other, which meditative practice can provide. Therefore, a goal of using technology to entrain the brain and align the frequencies of the brain hemispheres has become a very interesting avenue of science and experimentation.
I have a strange reaction to Binaural beats, as well as isochronic beats, and anything similar. After listening, I often feel vey fatigued, nauseous, and sometimes quite depressed. This effect can last a few days. So I stay away from it now, as well as guided meditations that have such beats in the background. Have you heard of this kind of reaction before?

Laughter releases endorphins that improve mood and decrease levels of the stress-causing hormones cortisol and adrenaline. Laughing tricks your nervous system into making you happy. Our suggestion: watch some classic Monty Python skits like “The Ministry of Silly Walks.” Those Brits are so hilarious, you’ll soon be cracking up, rather than cracking up.
Theta waves have a frequency between 4 and 7.5 hertz, making them slower than more wakeful alpha but faster than the dreamless slumber of delta. Theta brainwaves are the frequencies of nighttime dreams and REM sleep when the brain goes through bursts of activity and eye movement. People also experience theta waves in a state of light sleep, deep relaxation, during meditation and prayer, and when daydreaming. Theta waves produce an experience of inward wakefulness where we become disengaged from the outside world while engaging in inner activity. At the lower frequencies of theta, sleeping states are experienced, and at the higher range of frequency, awake relaxed states are experienced. 
This is an extreme example, naturally, but the idea holds true even in situations that are not as extreme. This ties in very closely with Point #4 above. When you’re wishing to combine meditation and brainwave entrainment, if you’re practicing a meditation technique but not really paying attention to what you’re doing, or perhaps you are performing the technique wrong, whilst allowing your mind to drift off to wherever it takes you, it should come as no surprise that the entrainment track is not helping you achieve a state of meditation. That’s because in fact you aren’t really trying to enter meditation or because you’re specifically engaging in activities that prevent you from getting there.
One can also learn to control and slow down their brain waves through various neurofeedback technologies such as electroencephalograph (EEG), galvanic skin response (GSR), and heart, pulse and breath rate monitors. These devices measure stress and relaxation parameters and then "play" back the signals to the user so they can use the signals as a beacon to guide and "steer" themselves into a relaxed state. This takes some time, work and discipline but is much quicker than learning meditation.
That said, I use binaural beats and isochronic tones to help me get over some hurdles, or as a pre-game to meditation. It’s far easier to go deep once my mind is operating on a certain frequency, or at least feels like it. It’s also way easier to get to that point than fighting my thoughts at times. Think of binaural beats and isochronic tones as heavy ammunition that you don’t always need, but is great to have in your arsenal when you really need it.

Binaural beats are the playing of two sine waves of close, but not the same, frequency into different earpieces of a set of headphones. The "beat" is heard as the brain tries to process them as a distinct sound, while taking into account the constructive/destructive interference. It is said to migrate brain waves to be closer to that frequency, like a sort of biological resonance, which is true. Of course the same can be said for listening to relaxing music help you relax, up tempo music to help you feel energetic, etc...
When your mind is all over the place, organizing your thoughts into a quick to-do list can help transfer the burden from your brain to paper. But for some people, seeing a long list of tasks can increase stress. Miller has another idea: a “stressor and action” sheet. “Fold a piece of paper in half length wise, and on the left column write ‘stressor’ and on the right hand column write ‘action,’” she says. “You will find as you write down thoughtful action steps to the things that are stressing you out, you regain authority over circumstance.” These are the signs you’re more stressed than you realize.
“When you play two separate frequencies in each ear, say 140 Hz and 149 Hz, the difference in frequency is 9 Hz. Your brain compensates for this difference, and a third tone of 9 Hz is experienced,” says Niraj Naik, founder of Trpynaural, a resource for binaural tracks. “This will result in your brain being raised or lowered and tuned into the desired frequency. This is how binaural beats are produced.”
Isochronic tones work by influencing your brainwave activity and they can’t directly affect the body. That said, the brain does control the body, so sensations and feelings can sometimes be felt in the body after stimulating your brainwave activity. Some people who are new listeners of this type of audio can sometimes feel tingling sensations in their body. Not everyone feels this and these sensations usually stop once you get more used to using the audios. Isochronic tones are considered as a safe technology. However, sometimes they can leave you feeling temporarily fatigued, especially if you listen to them for an extended period (hours) when you first start using them. If you felt fatigued, I would recommend using them for a much shorter period while you are getting used to them and ensure you are well-hydrated.
Brainwave entrainment is a colloquialism for such 'neural entrainment', which is a term used to denote the way in which the aggregate frequency of oscillations produced by the synchronous electrical activity in ensembles of cortical neurons can adjust to synchronize with the periodic vibration of an external stimuli, such as a sustained acoustic frequency perceived as pitch, a regularly repeating pattern of intermittent sounds, perceived as rhythm, or of a regularly rhythmically intermittent flashing light.