These are very similar to binaural beats, except that instead of the audio being fed through two different channels containing two different tones, monaural beats put both tones together on a single channel. The difference is that instead of your brain producing the effect of cancelling out the wave and producing the low frequency beat, it instead mixes in the air where it is perceived by the ears, with no brain processing involved.

OK – so some of this is pretty common marketing hype. Consumers have become almost numb to such hyperbole. But still we see some of the common – almost ubiquitous – elements of pseudoscientific scams. The company claims that the device is “effort-free”, that the results are “rapid and long-lasting,” that it is the “most effective” method of its kind, and that it is useful for a broad range of applications (hey, why limit the market). I am used to such hype about dishwashing detergent, but find it intolerable when applied to a pseudoscientific device with medical applications.
Cortisol is an arousal hormone, stimulating alertness and attention. Cortisol levels rise and fall in connection to circadian rhythms—cortisol levels rise to their peak levels first thing in the morning, just in time for you to be active for the day. Too-high cortisol levels are associated with insomnia, as well as more time spent in light sleep, rather than deep sleep.
... Several studies have looked at the possible effects of binaural beats within the alpha range on cognitive abilities. A significant improvement in cognitive processing, as measured by the Stroop Effect exercise, was found by a BB stimulation of 10.2 Hz frequency (Cruceanu & Rotarescu, 2013).Carter and Russell (1993)exposed 8 to 12 year old boys with learning disabilities to 8-week long 10 and 18 Hz BB stimulation sessions, and they found an improvement in Raven's progressive matrices and in a subtest of auditory sequential memory (Carter & Russell, 1993).McMurray (2006)assessed the effect of 7 and 11 Hz BB on alpha brainwave activity, working memory, and attention in healthy elderly people, who are known for experiencing gradual decrease in physiological alpha activity. The 2 minutes exposure to BB resulted in an altered electrical activity in the brain. ...

Why is exposure to these soundwaves helpful to sleep and relaxation? Science shows that exposure to binaural beats can create changes in the brain’s degree of arousal. Listening to these sounds that create a low-frequency tone, research indicates, triggers a slow-down to brainwave activity—and that may help you relax, lower your anxiety, and can make it easier for you to fall asleep and sleep more soundly.
Binaural beats by themselves are dull for some people to listen to. But with nature sounds or ambient music, as well as either white noise, pink noise, brown noise, mixed in with the binaural beats it is more pleasant to listen to longterm. Normally it will take about 6 minutes for the brain to start becoming entrained by the binaural beats. But it is best to listen to binaural beat recordings daily that are any where between 10 minutes to an hour long.
A popular opinion in the brainwave entrainment community is that listening to isochronic tones without music produces a much stronger effect.  However, in the study by Doherty, Cormac. “A comparison of alpha brainwave entrainment, with and without musical accompaniment” (2014),  it was concluded that brainwave entrainment was equally effective for isochronic tones, both with and without music.

♥ I've beeen training in self-hypnosis for a while (under supervision and for a reason) and found that the 8-4 Hz beats put me very quickly in a deeply relaxed state. Definitely the thing! With the timer, I can shut them for the real self-hypnosis. I haven't tried the other beat generators yet, but this one works much better than I expected and clearly does the job. In a few words: I'm impressed!
There were no significant differences between the experimental and control conditions in any of the EEG measures. There was an increase of the Profile of Mood States depression subscale in the experimental condition relative to the control condition (p = 0.02). There was also a significant decrease in immediate verbal memory recall (p = 0.03) in the experimental condition compared to control condition.
After nearly two years of daily use of this brainwave meditation and brainwave technology, I began to enjoy a quality of life–without medication–that once seemed quite impossible for me. I do not say this lightly. Not only did I enjoy a fulfilling life, I also experienced what seemed like significant development in self-concept, values, interpersonal skills, creativity, accelerated learning, intuition, ability to handle stressful situations, self-esteem, sense of purpose, and social awareness.
Further experimentation showed that the difference between the two frequencies must be relatively small – under 30 hertz – for it to be perceived as a “beat”; frequencies with greater difference are perceived separately. Using binaural beats in various mental states while being recorded by an EEG (encepl…blahFIX) allowed researchers to further delineate the different wavelengths the human mind generates for different states of being. The categories are generally agreed upon as (from most to least “active” states): Gamma (extreme emotions or intense concentration), Beta (active thinking, concentration, anxiety, arousal), Alpha (drowsy, falling-asleep feeling, sometimes also general relaxation), Theta (dreaming sleep or deep meditation), and Delta (deep, dreamless sleep), but the wavelengths at which each occurs are not set in stone, though they generally run as over 40 hertz for Gamma, 13 to 29 for Beta, 7 to 13 for Alpha, 4 to 7 for Theta, and under 4 hertz for Delta.
A more extensive study of over 100 participants who were undergoing general anesthesia for a day procedure, reported a decrease in pre-operative anxiety. The participants in this study listened to 30 minutes of binaural beats before surgery, but the researchers noted that people experiencing high levels of pre-operative anxiety could listen to binaural beats for up to 1 hour before anesthesia to reduce levels of anxiety.
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