While visual entrainment is more powerful than audio alone for inducing desired brainwave states, more caution is needed when using visual methods. Between 0.3 and 3 percent of the population is susceptible to having seizures from flickering light stimulation, and for other people, flickering visual stimuli simply makes them uncomfortable. People with epilepsy have a greater chance of having a seizure from exposure to flickering light stimulation.
How brainwave entrainment works is quite simple. A tone or beat is overlayed into a track (usually with nature sounds or calming music) that pulses on and off at a specific rate. The frequency of that rate is matched by the brain, thus leading it to produce brainwaves that correspond with that particular frequency. The specific frequency range determines the brainwave produced (ie: alpha, theta, delta, gamma). For example, if the beat is pulsing on or off at a rate of 7hz, your brain will produce brainwaves at the frequency of 7hz, which are theta waves.
In all professionally produced meditation programs, you train your brain gradually. That is how you successfully develop. Just like training the body, you progress gradually. This is the key. In BrainAscend you start with level 1. Each track is 30 minutes.  Use it once per day for 30 or 60 minutes at a time (once or twice in a row. Use repeat/loop function in your player) or twice per day for 30 minutes at a time. You should use every level for at least 2-3 months before moving to the next. The exception is level 1 which is an introductory level which you can use for a week or so. After that time, if you can repeatedly remain fully aware on your current level without falling asleep (even if playing it twice in a row) you can move on to the next level. Until then you should continue on your current level. Listen with closed eyes, either sitting up or laying down.

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. 

I am one of the fortunate ones who received a free demo of your product. I do believe your product corrected damage to my brain from a childhood concussion. Immediately upon use, I became aware of sounds, drainage and even discomfort behind my right eye and the lower right side of my skull. This continued for a week of using the product daily. I was about to give up using the product when all discomfort stopped, and has not returned. I do believe your product should be used for childhood head trauma. Even though the brain is only bruised, a life can be altered immensely. I love my Equisync II and will use it daily and with confidence.
So using the example track above, the right ear is sent a 20Hz beat, compared to a 10Hz beat in the left ear.  As the right ear receives the higher frequency of beat, this works to increase the speed of the ‘left' brain hemisphere, which can be helpful for people with conditions like ADD, who are often found to have an abundance of slow wave activity in the left brain.
It is important to take an objective look at published scientific evidence to determine whether brainwave entrainment is an effective treatment for certain conditions and/or symptoms. Most preliminary evidence suggests that while the technology will not cure any condition, it may be a successful adjunct treatment when used carefully with the proper protocol.
The technology transmits voice messages on close to ultrasonic frequencies that we can not consciously hear, directly into the subconscious mind, with no chance for the conscious mind to filter the information, making it powerful enough for subliminal control. This technology is now available for self improvement purposes with categories such as:  Self confidence, motivation, focus, stress relief, sleep and memory improvement. You can also get your very own custom subliminals to program yourself with anything you want. In 1996, Edward Tilton, President of Silent Sounds claimed that such technology had been used successfully even in military operations to make enemy troops lose morale and surrender. Now we use it for self improvement!
This is a question I have noticed to concern many people, who are researching the issue. I have come across this question in forums, Yahoo Answers, in blogs, and all other sorts of  places. I can definitely empathize with someone who is looking to find a solution to a problem like anxiety, migraine, pain, etc., and needs reassurance and scientific proof that brainwave entrainment actually works!
Different people have different requirements when it comes to frequency changes in the music and it's quite impossible for us to anticipate them all. We would need to produce so many different variants of all our music productions that it would be impractical to manage and confusing for our customers. For example, if we were to start raising the frequency from theta up to alpha between the 50-60 minute mark of a piece of music, this would be useless to someone who used the music for a guided meditation that was only 45 minutes long. In the early stages of the development of our brainwave entrainment music we had so many different requests from different people that we could only opt for the simplest solution, which is to use a consistent frequency throughout. It might not be the absolute "perfect ideal", but this is still a very effective technique and the feedback we've received on our brainwave entrainment music has always been exceptionally positive.
The most common way to use a brainwave entrainment is for a short-term benefit, to help guide your brain into a particular mental state at the time you need it.  In a similar way to how you might take a sleeping pill before bed to help you get to sleep, or maybe drink some coffee or an energy drink to help wake you up and give you a boost of energy.
I was diagnosed with “acute high anxiety, major clinical depression,and ptsd” 16 years ago. I have clinically addressed these disorders with a number of medications, which none have helped. I am so lucky I have found this simple easy to practice method of practice, that I have found these beats and tones so essential that I indoctrinated them into my daily life, and have come to the realization, that someday very soon I will awake and will not suffer from these burdens these disorders ever again.

The activity of neurons generate electric currents; and the synchronous action of neural ensembles in the cerebral cortex, comprising large numbers of neurons, produce macroscopic oscillations. These phenomena can be monitored and graphically documented by an electroencephalogram (EEG). The electroencephalographic representations of those oscillations are typically denoted by the term 'brainwaves' in common parlance.[4][5]