This phenomenon is best known in acoustics or music, though it can be found in any linear system: "According to the law of superposition, two tones sounding simultaneously are superimposed in a very simple way: one adds their amplitudes".[2] If a graph is drawn to show the function corresponding to the total sound of two strings, it can be seen that maxima and minima are no longer constant as when a pure note is played, but change over time: when the two waves are nearly 180 degrees out of phase the maxima of one wave cancel the minima of the other, whereas when they are nearly in phase their maxima sum up, raising the perceived volume.
When you hit a tuning fork, tuned to a particular sound frequency such as the note B, and hold it close to the strings of a guitar, you will notice that the B string on the guitar will vibrate because it has entrained on to the same frequency of the tuning fork. Interesting enough, the other strings will not vibrate. Only the one with the same tuning as the tuning fork.

When you're having a hell of a day—good or bad—checking out for 10-15 minutes is revitalizing. Find a place where you can be alone (and definitely ditch the cell phone)—the attic, the bathroom, a quiet cafe, a big oak tree—and wipe the slate clean for a few minutes. Do whatever it is that relaxes you: Meditate, read a novel, sing or sip tea. It's crucial to take just a few minutes everyday to de-stress. It's not how much time you allot, but being consistent that's important.
The various mental states of the individual are thought to take place across a varied range of frequencies, or brainwaves. By encouraging the frequency following process, entrainment is able to create positive change in the brain, through matching carefully-selected frequencies of light and/or sound. The stimulus enables the individual to access a different state of consciousness, which can be useful for a number of benefits including relaxation, anxiety management, stress reduction and more.
Go behind the scenes of brainwave entrainment technology creation with Joseph Kao, developer of the extraordinary meditation tool Journey to the Center of the Self. Here, in an interview with John Dupuy, CEO of iAwake Technologies, Joe describes the amazing complexity of the brainwave entraining soundscape he created to both accompany his deeply inductive, 30-minute, guided meditation on the first track of Journey, and also stand alone as a music-only track that holds you in a profoundly relaxed, still, yet clear place on the theta/delta border. To find out all that went into the making of the inductive guided meditation on the first track of Journey, see A Guide to Transpersonal Meditation: Journey to the Center of the Self, part I of this interview.

When people begin to believe these kinds of claims it is only half a step further for them to begin to attribute all of their own curious little experiences to entrainment. After all, they reason in the back of their minds, if 3.84Hz can cure an ovarian cyst, isn’t it just as reasonable that listening to a track at 8Hz might cause the room to appear to spin and change colors? There is an old saying that suggests that the more outrageous a claim is, the more people will be inclined to believe it. Don’t fall for outrageous, ridiculous claims. If you do you’re heading for disappointment, guaranteed.
This app offers an easy to use interface that helps you achieve certain states of mind for different activities. From headache treatment to IQ boost to Sleep Induction and Relaxation, this app offers frequencies for over 25 scenarios. If you’re looking for an app that will let you choose a state of mind or activity and then just hit play, this app would be great to use.
John Dupuy is the CEO of iAwake Technologies and travels internationally to teach and inspire on the subjects of Integral Recovery, Integral Transformative Practice, and the use of brainwave entrainment technology to deepen one’s meditation practice and in the treatment of addiction, depression, and PTSD. John is the founder of Integral Recovery® and his book Integral Recovery: A Revolutionary Approach to the Treatment of Alcoholism and Addiction  won the 2013 USA Best Book Award. John also hosts interviews with leading innovators in the spiritual technologies field on Spiritual Technologies 2.0 Live and co-hosts the popular Journey of Integral Recovery podcast.
♥ At 56, I have tried many a thing. The default setting of Binaural Beat Machine does make me very relaxed. But it's not what it does on the moment, pleasant as this might be. It is the quality of the sleep, when I use it for half an hour before going to bed. I sleep a deep, restful sleep. I use it during day-time meditation as well, and the clear-mind feeling about an hour later is wonderful!
This music encourages a state of delta relaxation. Delta brainwaves are most prevalent during deep, dreamless sleep. The delta state is a mostly unconscious state that is essential to one’s physical, emotional, psychological and spiritual wellbeing. People who are able to achieve a state of delta relaxation through meditation will sometimes describe spiritual encounters and out of body experiences. The delta state is perfect for inducing profound spiritual experiences, healing and deep subconscious repatterning. Delta frequency brainwave entrainment music is also a fantastic cure for insomnia.
I was raised on a farm, and in my youth I dug enough fence post holes to last a dozen lifetimes. My father used to joke that he gave me that chore so that I’d have lots of practice and get good at digging fence post holes. From a pragmatic point of view, the purpose of digging all those post holes was really not so that I’d become a better post hole digger, but so that I could plant posts in them. Once you dig a post hole to the correct depth you don’t keep on digging, trying to make the hole fancier or more aesthetically pleasing. You stick a post in that sucker, tamp the earth back in around it so that the post is secure, and then move on to dig the next hole.

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.
A warning: Be sure to listen to these two tracks no more than twice each per day. Any more and your beta-thought centers can have TOO much energy in them, causing you to feel like you are on a stimulant. Some people may only be able to listen to each track once per day without feeling over-stimulated. That's fine, just go with what works for you. Sometimes less is more when it comes to brainwave entrainment. Don't push too hard trying to force-grow your brain cells. :-)

With digital upgrades, Berger’s machine is still in use today, known as an electroencephalography machine, or EEG. Berger used his machine to study the brains of psychologically normal and abnormal people and discovered the first brainwave, called the alpha wave and also known as the Berger wave, along with the faster beta wave, which he observed suppressing the alpha wave when subjects opened their closed eyes. 
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.
Meanwhile, the therapeutic benefits of listening to sound and music is a well-established principle upon which the practice of receptive music therapy is founded. The term 'receptive music therapy' denotes a process by which patients or participants listen to music with specific intent to therapeutically benefit; and is a term used by therapists to distinguish it from 'active music therapy' by which patients or participants engage in producing vocal or instrumental music.[37] Receptive music therapy is an effective adjunctive intervention suitable for treating a range of physical and mental conditions.[38]
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