This is probably the most popular choice of frequency. The theta state is a state of tremendous stress relief. The benefits associated with theta level relaxation include improved concentration, reduced hyperactivity and improved memory. While in a state of theta relaxation, one’s blood pressure, breathing and heart rate all slow to a much more restful and healthy level that promotes natural healing. During theta relaxation one may also experience vivid flashes of mental imagery as the mind opens to memories or subconscious information that is not available to the conscious mind during the normal waking state. The theta state is a very deep state of relaxation that is excellent for deep hypnosis and mental programming.
When you hit a tuning fork, tuned to a particular sound frequency such as the note B, and hold it close to the strings of a guitar, you will notice that the B string on the guitar will vibrate because it has entrained on to the same frequency of the tuning fork. Interesting enough, the other strings will not vibrate. Only the one with the same tuning as the tuning fork.
Hi Et, In all the feedback and studies I’ve read and looked into over the years, I’ve seen lots of feedback from people talking about how they don’t like the sound of the tones, or they find them irritating in some way. Unfortunately, there doesn’t seem to be any particular reason why one person likes it and the next doesn’t. It’s a bit like normal music, one person’s sweet symphony is another person pneumatic drill. It’s common for people to find it weird and maybe annoying at first, which is how I felt in the beginning. But usually after a few listens you can start to get used to it and appreciate the sound, and especially the feeling it gives you. Personally, I think it can help if you try to embrace the sound, psychologically speaking beforehand. It can also help to have the sound playing at a very low volume, to begin with, then building it up as you get more used to it.
Cognitive behavioral therapy (CBT) is a type of therapeutic practice that has been proven to lower anxiety, stress and multiple disorders — including addiction, eating disorders, insomnia and depression. Knowing that at least 50 percent of the time experiencing a mental disorder is due mostly to chronic, untreated stress reactions, therapists use CBT to train all types of people to better react to situations that are stressful.
  That said, you achieve the best results when you listen to the tones in a relaxed, quiet environment, investing your complete attention to the tones and the effect they have on your inner self. Experts recommend that even isochronic tones be heard via headphones to cut out distractions from external noises. The best thing to do is give it your entire, undivided attention, so that you can experience the outcomes quickly and easily.
Slightly higher-frequency entrainment can lead to hyper suggestive states of consciousness. Still higher-frequency EEG states are associated with alert and focused mental activity needed for the optimal performance of many tasks. Perceived reality changes depending on the state of consciousness of the perceiver (Tart, 1975). Some states of consciousness provide limited views of reality, while others provide an expanded awareness of reality. For the most part, states of consciousness change in response to the ever-changing internal environment and surrounding stimulation. For example, states of consciousness are subject to influences like drugs and circadian and ultradian rhythms (Rossi, 1986; Shannahoff-Khalsa, 1991; Webb & Dube, 1981). Specific states of consciousness can also be learned as adaptive behaviors to demanding circumstances (Green and Green, 1986).  
If brainwave entrainment leaves you with unwanted side-effects (see below) or discomfort, you’re probably encouraging a range of brainwaves that are already excessive in some area of your brain. The way around this is to get a brain map to see what your brain’s strengths and weaknesses are, and see what (if any) brainwaves could use some encouragement. 
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