Brain Entrainment

What it is
Psychoacoustics, or brain entrainment technology, is a way of recording sounds that influence cortical brain frequencies, and thus make subtle changes in the listener's state of consciousness. Particular states of consciousness are linked to combinations of electrical frequencies in the brain. The link works both ways; changing state of consciousness alters the frequencies, and also sounds fed in through the brain’s auditory system, if they are of a rhythmic nature, tend to entrain the frequencies to their own speed, and thus cause a consciousness shift. It should be pointed out, though, that the state of consciousness is somewhat elastic, and will tend to spring back unless the entrainment is suitably positive and sustained. Of course, the listener’s thought processes are a key factor in the state that will be entered – the psychoacoustic entrainment can help in a shift of state, but it cannot compensate for a thought process which is pulling in a different direction.

The frequency bands
The frequencies that are most influential over state of consciousness are lower than the human ear is capable of detecting directly, that is, below 30 cycles per second. Scientists have divided them arbitrarily into four bands, each identified by a Greek letter. Research has shown the kind of state that a person tends to be in when the strongest or dominant frequency is in a particular band. The bands are (highest first):

Beta	Everyday consciousness, active, problem solving
Alpha	Day-dreaming, creativity
Theta	Meditation, hypnosis, physical lethargy
Delta	Deep sleep

The non-dominant frequencies, i.e. those of lesser amplitude, are also important in determining the exact state which is being experienced.

Methods of entrainment
As the most of the frequencies that are of interest here are below human hearing range, most psychoacoustic engineers use indirect methods to register the desired frequencies on the brain. Some psychoactive CDs contain actual frequencies as low as 10Hz, but these do not register on the ear and are only effective when speakers are used, and are detected by the body rather than the ear; they also are lost when MP3 compression is carried out.

The most popular indirect method is the binaural beat. This makes use of a phenomenon where two slightly different frequencies (called "carriers") are chosen and each fed to one ear of the listener. This causes the brain to perceive a “ghost” frequency which is the difference between the two frequencies actually heard.

Although the binaural beat is very widely used, it is not a very efficient means of obtaining entrainment, and most CDs that use it in fact employ a whole stack of binaural beats using different carrier frequencies.

Our entrainment philosophy
We have a philosophy that differs somewhat from most of the other producers of psychoactive CDs. We use no subliminal effects whatsoever, because we are not trying to persuade anybody about anything. Where we use musical sounds, they are within the mainstream of melody and harmony; we find that many people are not at totally ease with the slightly weird metamusic that is commonly heard on CDs like this. And we do not use binaural beats – we prefer to use stereo crossfeed and isochronic pulsing, and to keep the whole sound harmonically integrated and as consonant as possible.