Borislava
You have several mechanistic conception of man.
Humans are the most flexible creature on the planet with a remarkable ability to adapt. This means that the brain in a very short time (measured in seconds) time to adapt (that is, begins to ignore) to any frequency (of course, in the framework of a range of capacities).
An effective program of audio-visual (auditory) stimulation is a dance of frequencies, higher and lower, sometimes with unexpected jumps.
In this respect, audio-visual (visual) stimulation significant gains in efficiency have auditory, not only due to different supply channels (which allows in some way to summarize the power), but the variety of patterns of stimulation. For example, varying the colors and the duty cycle can be a long time to stimulate the brain to a particular frequency. However, in most cases, it is only a scientific interest...
In General, programs on self-hypnosis are based on gradual decrease of frequency of stimulation of 15-18hz to the lower alpha frequency (around 8 Hz), followed by "dancing" around this frequency. Of course the theta frequency are more interesting to induce ISS, but we must bear in mind that the normal human brain is able to follow frequencies in the range 8-25 Hz, i.e., theta-frequency stimulation is almost useless. "Almost" - because the brain is able to tire of prestimulation and "fall" into a state of diffuse inhibition of the cortex. Feels quite nasty as, "out of the bed raised, but forgot to Wake up", but some like...
Another way to build an effective program can serve as a periodic wave-like frequency decrease of stimulati, starting somewhere in the 15-18hz up to 8 Hz. For example, something like: 18-16-17-14-15-12-14-10-12-9-11-8(Hz). For about 45 minutes, with progressive time intervals. Then the brain gradually "inertia" itself goes into the theta range and get as much more pleasant and productive than when diffuse inhibition of the cortex.
If you take the data mapping frequencies during, say, the hypnotic trance, it is quite "hopeless" picture.
For example, in the occipital lobes is dominated by beta frequencies (because they have a striking visual images), secondary zones, with some stretch, is dominated by alpha-frequency, and frontal theta. According to research on the perception of the sound frequency, the higher the tone, the closer to the frontal lobes are the areas responsible for the perception of these sounds, and Vice versa. Thus, before wishing to simulate these conditions through sound occurs very non-trivial task - to organize the beta stimulation at low sounds, the alpha or the sound of the middle range (this is, of course, not a problem) and theta sounds in the high range. The nontriviality is due to many factors, starting with the restrictions imposed by the Nyquist theorem, to various physiological effects, which cause the low-range sounds. For example, it is known that the greatest number and severity of diseases are the musicians playing on instruments with low sound... However all this can be overcome with some persistence, and special knowledge, as well as the opportunity to experiment. For example, in one of the devices manufactured over the hill for a variety of hypnotists, theta frequency serves to the auditorium through normal speakers, on the carrier 12kHz. But
here there is some funny table on the impact of frequency...
Good luck!
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