The mechanism for this is that when your eyes or ears are exposed to a particular frequency of pulses or beats, the thalamus first distributes this information to the entire brain, including the visual and cerebral cortex where neural activity begins to synchronize to the incoming frequency, producing hemispheric synchronization and a balance of brainwave activity across the brain.

The Transparent Corp forum – This forum is an invaluable resource for any brainwave entrainment user or enthusiast.  Most of the feedback is obviously focused on the Transparent Corp software, but with over 20,000+ posts now you can find answers to the whole array of brainwave entrainment questions on there.  (UPDATE: Sadly, the Transparent Corp forum has now been taken offline)
You listen to binaural beats using headphones. In each ear, you receive sound at a slightly different frequency (often accompanied by some relaxing background sounds). If your left ear receives a 300-hertz tone and your right ear receives a 280-hertz tone, your brain will process and absorb a 10-hertz tone. That’s a very low-frequency soundwave—one you can’t actually hear. But you don’t need to hear the sound for your brain to be affected by it.
When delta waves are present, our awareness of the external world decreases and shuts off. People with ADD have problems with delta waves occurring when they are trying to focus, and focus and attention become increasingly impossible with stronger delta waves. Studies show a reduction of anxiety, improvements in insomnia, and elimination of headaches when people engage in sessions of delta brainwave entrainment.
That is generally where the science ends and the pseudoscience begins. A number of companies and individuals have then extrapolated from the phenomenon of entrainment to claim that altering the brain waves changes the actual functioning of the brain. There is no theoretical or empirical basis for this, however. Entrainment is a temporary effect on the synchronization of neuronal firing – it does not improve or increase brain functioning, it does not change the hardwiring, nor does it cure any neurological disorder. There is no compelling evidence for any effect beyond the period of entrainment itself.
In other words, you give the well a little taste of what it is you want from it, and then the well responds by delivering more of the same back to you. In the case of the water well, you pour a small amount of water down into the pump. This is known as “priming” the pump. Until you do this the pump does not produce the water you’re looking for. Once you prime the pump it sets up the conditions in which that pump can do its job and the water begins to flow.
Pure tones played together interfere with each other when they are close in pitch but not identical. When each tone is sent to a different ear, there will not be any physical interaction between the waves, yet your brain still creates an interference inside your head: the so-called binaural beat. In order to create a binaural beat, each ear must receive its dedicated signal. Therefore, binaural beats only work through headphones.
Theta waves have another interesting characteristic. The Earth has a measurable resonance of 7.83 hertz known as the Schumann resonance. Because the Schumann resonance is a constant background frequency surrounding all life, it may play a special role in biological activity. The Schumann resonance frequency falls within the range of theta brainwaves and may have something to do with why these brainwave frequencies are so powerful. 
In physics, entrainment is the process of two oscillating systems coming to assume the same periodic rhythm, such as is observed when two clocks slowly synchronize their ticking and tick together in harmony after some time. Pendulums also achieve this same synchronicity when swinging in close proximity to one another, a phenomenon first observed and written about in 1665 by Christiaan Huygens, a Dutch scientist.

One of my habitual ways to unwind, get into an easy meditative state, and let the stress of the day melt away is by listening to binaural beats from these guys. So please do try them out! Their work is of the highest quality. (Note: yes, our website does earn affiliate commissions from them, but I only recommend them because I personally use their music to help relax my mind and reduce nervous tension – and it works!)
Stress levels and a proper diet are closely related. When we’re overwhelmed, we often forget to eat well and resort to using sugary, fatty snack foods as a pick-me-up. Try to avoid sugary snacks and plan ahead. Fruits and vegetables are always good, and fish with high levels of omega-3 fatty acids have been shown to reduce the symptoms of stress. A tuna sandwich really is brain food.
Progressive muscle relaxation is a two-step process in which you systematically tense and relax different muscle groups in the body. With regular practice, it gives you an intimate familiarity with what tension €”as well as complete relaxation €”feels like in different parts of the body. This can help you react to the first signs of the muscular tension that accompanies stress. And as your body relaxes, so will your mind.
I have many new age, meditation, classical and jazz cds that I use for relaxation. This Steven Halpern cd is now my favorite one. I can listen to it for hours on end while I read, write, use the computer, or just veg out on the couch at home or lounge at the pool. I especially love the tracks with the ocean wave sounds mixed in with the electronic music. I definitely am in the theta brain wave state while listening to it, and I know that's the reason it is so much more soothing than any other cd that I own. It is really great for eliminating any anger or anxiety that I may be feeling. I believe it's also improving my sleep. I give this cd the highest possible recommendation!
“A quite different phenomenon results when stereophonic earphones are used and the signals are applied separately to each ear. Under the right circumstances beats can be perceived, but they are of an entirely different character. They are called binaural beats. . . . Binaural beats require the combined action of both ears. They exist as a consequence of the interaction of perceptions within the brain.”

Changes in neural oscillations, demonstrable through electroencephalogram (EEG) measurements, are precipitated by listening to music,[20][21][22][23][24][25] which can modulate autonomic arousal ergotropically and trophotropically, increasing and decreasing arousal respectively.[26] Musical auditory stimulation has also been demonstrated to improve immune function, facilitate relaxation, improve mood, and contribute to the alleviation of stress.[27][28][29][30][31][32][27][33] These findings have contributed to the development of neurologic music therapy, which uses music and song as an active and receptive intervention, to contribute to the treatment and management of disorders characterized by impairment to parts of the brain and central nervous system, including stroke, traumatic brain injury, Parkinson's disease, Huntington's disease, cerebral palsy, Alzheimer's disease, and autism.[34][35][36]