So my question is: Why? When I read it, I had a bit of a fear of brain aneurysms. Therefore, 1. could someone contact me to tell me why use of your product shouldn’t continue past 2 hours? [I probably won’t heed the reason unless it’s a life or death warning: I love this product that much!] 2. Please feel free to post my letter in your testimonials, if you ever decide to post such customer comments.
I love your tapes! I bought them a few weeks ago and have greatly benefited. I’m also a holistic practitioner and have recommended them to a number of patients. And today when I made my last referral to your website for them to purchase from, it occurred to me that perhaps you have referral discounts, or wholesale prices for practitioners, and that I should ask?
Theta stimulation: There appears to be no benefit associated with using theta stimulation for cognitive functioning, mood, or stress relief. While theta may be a useful way to induce sleep or alter your state of consciousness, there really isn’t much science supporting entrainment in this particular range for most purposes. Photic stimulation of theta between 5 Hz and 7 Hz can be useful for headaches.
To summarize all this, we can see that the type of product you choose plays an important role in answering that question – “Can brainwave entrainment damage my brain?” My personal advice as a long-term user of the technology is to Be selective about what brainwave entrainment audios you download from the internet, and make sure to follow the instructions! 
I wouldn’t personally recommend listening to delta wave frequencies for depression, so I’m not sure who advised you to do that? People with depression usually have a higher ratio of theta and delta wave activity, so I would normally recommend listening to high alpha wave and low beta wave frequencies, to help balance things. I have some 10Hz alpha tracks for serotonin release, which you can try for free on my YouTube channel here: I also recommend you give these SMR (low beta wave) tracks a try: I hope that helps.
There basically are a few things that you can use to deduce whether you think these claims are true, and will work for you.  A few manufacturers of this type of product have taken the time to hook up experienced meditators (like zen monks) to encephelographs, then fashion their audios to mimic what is occurring in these deep meditators’ brains.  It would make sense then, to a large degree, that you could experience similar benefits from your brain undergoing this process. 
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The Frequency following response (FFR), also referred to as Frequency Following Potential (FFP), is a specific response to hearing sound and music, by which neural oscillations adjust their frequency to match the rhythm of auditory stimuli. The use of sound with intent to influence cortical brainwave frequency is called auditory driving,[39][40] by which frequency of neural oscillation is 'driven' to entrain with that of the rhythm of a sound source.[41][42]

Basically, the brain produces a phenomenon that results in low-frequency pulsations in the amplitude (volume) and sound localization of a perceived sound when two tones at slightly different frequencies are presented separately, one to each of a person’s ears, using stereo headphones.  A beating tone will be perceived, as if the two tones mixed naturally, out of the brain. The frequencies of the tones must be below 1,000 hertz for the beating to be noticeable. The difference between the two frequencies must be small (less than or equal to 30 Hz) for the effect to occur; otherwise, the two tones will be heard separately, and no beat will be perceived.
Delta brainwaves have the slowest frequencies, ranging between 0.1 and 4 hertz, and these are the brainwave states associated with deep sleep, trance states, and unconsciousness. Few people can remain awake during delta brainwaves states, although this state is recorded in awake infants between ages of three months and one year and also in babies just before birth. Delta waves are also linked with increased production of HGH, DHEA, and the neuro-transmitter serotonin.
Alpha brainwaves are resonating just below beta brainwaves at the frequency range of 8Hz to 12Hz on an EEG. Beta brainwaves are the normal, waking life, active, rational thinking and problem solving brainwaves that are dominant in most people throughout the day. Alpha brainwaves begin to show up when relaxation occurs. Often times the simple act of closing your eyes can product spurts of alpha waves. Taking a few deep breaths or consciously relaxing will do the same. When alpha waves become dominant, the body and mind are usually comfortably relaxed.
NeuralSync™ is the ONLY technology that utilizes FOUR SEPARATE yet synergistically-interactive frequencies precisely calculated to induce each mental state offered in our catalog. Our exclusive 4-W.T.S.P.™ technology creates waves in a balanced 4-dimensional pyramid that are collectively complementary and interactive. Unlike other related programs that use only a single binaural beat or isochronic tone frequency (or several in sequence), NeuralSync™ applies all four simultaneously to immerse your brain into targeted and harmonizing perspectives.
Deep relaxation is a major benefit resulting from the brain’s cortical frequency following response. By selecting the desired rate the brain, via the frequency following response, will tend to mimic the rate it is exposed to and thus enter that brainwave state. This helps to explain why this technology can produce benefits commonly found with meditation. One of the most valuable benefits of consistent  brainwave entrainment is that we are able to experience and recognize the various states of consciousness. With practice we can learn how to re-create these states.
Different states of mind are associated with specific brainwave frequencies that would be inaudible if played directly. These frequencies can be induced in the brain indirectly by playing two different audible tones into each ear, which after being processed by the brain, are perceived as an inaudible beat matching the target brainwave frequency. As you listen, your own brainwaves fall into step with this inaudible beat, and after a few minutes synchronize with the target brainwave frequency. Brain Wave's 35 programs layer these binaural sequences into multi-stage sessions that have helped thousands of people focus and concentrate, feel positive and motivated, and sleep more soundly.

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.

The eyes of the participants were closed and the VFP goggles illuminated in alternative manner; first the right eye, then the left. The rate at which the photic stimulation was conducted ranged between 0.5 Hz and 50 Hz. Of the 50 patients with migraines, 49 considered their headache as having been “helped” by the stimulation and 36 noted that their headache had completely “stopped” from the VFP goggles.

How does brainwave entrainment work? Consistent, precisely engineered audio frequencies in the form of binaural beats cause the brain’s frequencies to match the stimulus. Your brain perceives two beats with slightly different frequencies (which are inaudible to the ear) through your headphones. It takes the difference between the two, and matches its own frequency to it. This is called the “frequency following” response.
Targeted hemispheric changes: Some speculate that specific alterations in brain waves can be made on an individual basis. In other words, you can target one frequency in one hemisphere (via the right ear) and another distinct frequency in the other hemisphere (via the left ear). The left ear affects the right hemisphere and right ear affects the left hemisphere.
Scalar waves are a constantly regenerating energy source that imprint a signature on your body with lasting positive effects. They strengthen chemical bonds within DNA, making it more resistant to damage and cleanse blood and cells to improve immune function. They impart energy that helps mental focus, and increase amplitude of all EEG frequencies, but particularly the lower levels where deep rejuvenation, relaxation and healing occur. They leave you feeling refreshed and energized, with lasting pleasant sensations that continue long after each brainwave entrainment session.
These sounds in these musical tracks are presented through monaural beats, binaural beats, isochronic tones, or a mixture involving combinations of all three of these modalities, described in detail below. Choose alpha brainwave tracks for calming anxiety and relaxing body and mind, and choose theta tracks for help in getting to sleep and for bringing hidden feelings to the surface. Some people also report out-of-body type experiences when in theta brainwave states.
Holosync is often seen as the ‘gold standard’ of brainwave entrainment. The Holosync program features 13 different levels which are listened to for 4-6 months before your brain will have adjusted enough to the technology to be able to move on to the next level up. Starting at level 2 of the program, Holosync goes the extra mile by incorporating your own chosen positive affirmations – recorded in your own voice.
First of all thank you for your amazing website, I have a question regarding these matters, I can make both binaural beats and isochronic tones for myself but I doubt for low frequencies states (Theta and Delta) which one is better? Because I searched a lot and saw that binaural beats are better for low frequencies and for high frequencies (Beta Gamma Lambda….) isochronic tones are more effective. Also, for Alpha states some said isochronic and other said binaural.
We’ll use Holosync® to place you in an alpha brain wave pattern, that of focus, concentration, and accelerated learning. You’ll become completely absorbed in whatever you’re reading—or, for that matter, in anything you do requiring focus and concentration. And, you’ll remain refreshed even after hours of concentration. Quietude™ will dramatically increase your productivity and learning ability.
Isochronic tones and Monaural beats are now being considered by many to be more effective and more useful in brainwave entrainment technology. Monaural beats, unlike binaural beats, only use one beat. It is said that these are easier on the brain, and help to induce a specific brainwave state faster and more effectively, as the brain does not need to go through the process of reconciling two different frequencies. 
By exposing an individual to repeatedly external stimulus which can be flashing lights and/or recurring sounds, the entrainment process consists in pushing the brain to adjust to match the frequency provided. Unlike other forms of neurotherapy which require the individual to actively respond to stimulus, entrainment creates an immediate neurophysical response which is instinctive and effortless for the person being provided with the light and/or sound combinations. The key outcome of the sensory stimulation is known as the ‘Frequency Following Response’.
The brain has two hemispheres that operate somewhat independently from one another. The two hemispheric structures of the brain are connected by a large nerve, called the corpus callosum, which sends information back and forth between the two sides of the brain. In most people, the left hemisphere controls language, logical thinking, and analytic processes and the right side contains the centers for emotion, intuition, and non-linear creative thinking.
When the body-mind effects from experiencing AVE are fully appreciated, the experience becomes as regular and beneficial as many other life essentials such as quality sleep, good nutrition, pure water and exercise. Sleep is another area where AVE has been shown to be beneficial, contributing to the natural regenerative process of the body and brain.
Your brain operates at certain levels of activity – the normal waking, active Beta, the meditative Alpha, the asleep-and-dreaming or deep meditative Theta, and the deep sleep/unconscious Delta. Beta is characterized by one thing we all want to get away from – stress.But that brainwave state has its place. It’s the action mode, and that’s the way it should be! If we’re not alert when we’re awake, bad things can happen, right?