Isochronic tones work just the same in delta as they do in alpha, theta and beta and they are widely used in the brainwave entrainment community to help people sleep. Like you, I’ve also seen some websites saying they don’t work in delta, but it’s a bit like the game of Chinese Whispers, where someone makes a comment and then after it gets passed around and shared a lot the message gets distorted and appears to be a fact. I don’t know of any scientific reason why they wouldn’t work in delta. I remember some people talking about this on a brainwave entrainment forum many years ago. They were saying they found isochronic tones a bit too abrupt for using to help them sleep and they preferred binaural beats, as they thought they were a more soothing sound. That was just a personal preference shared by a couple of prominent forum members at the time and some people then took that as a fact for everyone. That’s where I think that belief originated from.
Binaural beats are pretty simple. Basically, you take two frequencies that are similar and play each one through it’s own stereo headphone. The two competing frequencies will work together in your mind to produce a pulsing. That pulse will be a certain frequency that corresponds to a number in hertz that is linked to what your brain produces when you are in certain states of consciousness.
This music encourages a state of alpha relaxation. The alpha state is a pleasant state of relaxed alertness. It’s a state that many people experience when they are waking up in the morning or when they are just beginning to drift off to sleep at night. While in a state of alpha relaxation, the mind is quite clear and receptive to information, learning is accelerated and one’s sense of creativity is enhanced. The mind is also very open to positive suggestions during this state.
Most of all, don't feel bad if you fall asleep. Your brain is still receiving many of the benefits of entrainment while you sleep through the audio tracks. In fact, many people report better, more restful sleep when they use brainwave entrainment to help them fall asleep. However, I recommend that you do not go to sleep with your brainwave track set to repeat, as that can be too much stimulation for the brain.
Alpha (12hz – 8hz) – Awake, but deeply relaxed. Simply closing your eyes will produce alpha brainwaves. This category is associated with daydreaming, visualization, imagination, light meditation. Brainwave expert Anna Wise called the alpha range the bridge between beta and theta. (More information can be found in Wise’ book The High-Performance Mind)
So, there’s the deep stuff here, and then there’s the gamma stuff, too. There’s a little bit of 80 Hz, but it’s primarily a 40-Hz gamma track, gamma frequencies that are combined with a pulse, on and off, throughout the recording. I went to some lengths to make this as rich and potent as I could, whilst blending it into the sound of the music. There are these really rich, kind of cat-purr-like vibrations that come through at times, combined with the lulling, deeply relaxing theta brain waves.
Binaural beats can easily be heard at the low frequencies (< 30 Hz) that are characteristic of the EEG spectrum (Oster, 1973). This perceptual phenomenon of binaural beating and the objective measurement of the frequency-following response (Hink, Kodera, Yamada, Kaga, & Suzuki, 1980) suggest conditions which facilitate entrainment of brain waves and altered states of consciousness. There have been numerous anecdotal reports and a growing number of research efforts reporting changes in consciousness associated with binaural-beats. "The subjective effect of listening to binaural beats may be relaxing or stimulating, depending on the frequency of the binaural-beat stimulation" (Owens & Atwater, 1995). Binaural beats in the delta (1 to 4 Hz) and theta (4 to 8 Hz) ranges have been associated with reports of relaxed, meditative, and creative states (Hiew, 1995), and used as an aid to falling asleep. Binaural beats in the alpha frequencies (8 to 12 Hz) have increased alpha brain waves (Foster, 1990) and binaural beats in the beta frequencies (typically 16 to 24 Hz) have been associated with reports of increased concentration or alertness (Monroe, 1985) and improved memory (Kennerly, 1994).
The studies included in the recent reviews of Tai Chi and yoga indicate that sessions between 60 and 90 minutes performed 2 to 3 days per week were effective in reducing stress and improving feelings of well-being (7,14,17). A study conducted in a worksite environment showed that 15 minutes of chair-based yoga postures was effective in reducing acute stress when assessed by self-report and with physiological measures (e.g., respiration rate and heart rate variability parameters). This finding indicates that shorter duration sessions can be effective in reducing acute stress with this type of exercise (15).
When tuning instruments that can produce sustained tones, beats can be readily recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. As the two tones gradually approach unison, the beating slows down and may become so slow as to be imperceptible. As the two tones get further apart, their beat frequency starts to approach the range of human pitch perception, the beating starts to sound like a note, and a combination tone is produced. This combination tone can also be referred to as a missing fundamental, as the beat frequency of any two tones is equivalent to the frequency of their implied fundamental frequency.
This depends on how ready your brain is to absorb the impact of the tones and how responsive it is. Most people experience a feeling of relaxation and calm right from the first session. The degree to which you feel these hinges on how well your brain reacts. Use it over a few days and you can experience unmistakable signs of stress reduction and improved clarity of mind. After a while, when you brain gets trained in allowing better communication between the right and left hemispheres, you will sense that the feeling of mental clarity and calm carry forward even hours after a session.
It cannot be any wonder then that we are almost desperate to find some sign, some indication that meditation and brainwave entrainment is having tangible, definable effects. We seize on these odd little experiences like ‘flushing of the face’ or ‘seeing spirals of color’ when our eyes are closed, hoping these are signs suggesting the elusive relief we’ve been after is finally within our grasp. We ask others to validate our experiences so that we can reassure ourselves we’re on the right track at last.
Practitioners are discovering a number of different areas in which entrainment therapy may bring positive benefits. From managing mental health more effectively through to providing increased mental focus and concentration, it is thought the technique can be adapted according to the specific issues being treated. An improved immune system, enhanced levels of pain management, and a reduction in autoimmune disorders are also thought to be achieved through the therapy, leading many individuals with chronic ill health to consider brainwave entrainment as a non-invasive yet effective therapy.
Brainwave entrainment is used by millions of adults across the world with no negative effects. However, as with any treatment or therapy, individuals who are prone to seizures should avoid these tones. It is also not advised for pregnant women or very young children whose brain is still developing. If you are concerned about health impacts, discuss it with your health practitioner before you start using our brainwave entrainment products. It is also very important that you use the products in accordance with our instructions.
...  While entrainment by binaural auditory beats in the alpha frequency has also been shown to enhance creativity, cognition, memory, and an improvement in intelligence tests and achievement tests in learning disabled boys.  The gamma-band activity has been shown to involve in a variety of functions such as attention, memory, and consciousness. Current literature suggests that entrainment by gamma beats promotes cognitive flexibility, modulates visual attention, and enhances creativity. ...
In addition to the exercise prescription, other characteristics of the exercise session (e.g., group vs. individual) and the individual also are important considerations. Because of health consequences associated with stress, high-stress clients are likely to be at increased risk for cardiovascular disease and cardiovascular events during exercise. Therefore, using the preexercise screening procedures outlined and endorsed by the American College of Sports Medicine is essential (1). Monitoring exercise intensity for those looking to “blow off steam” to reduce stress might be a concern when the client has high blood pressure or other cardiovascular risk factors that further the risk increase for cardiovascular events.
With the binaural beats, this may be difficult to do since you need to listen to the twin frequencies and allow your brain to create a third one to bridge the gap. Ideally, you will be listening to these beats through headphones so carrying out other work may be challenge. However, with isochronic frequencies, the tone can be heard without headphones which means you can run the mp3 with a speaker and allow it to play in the background as you carry out your work. Of course, activities such as driving or operating heavy machinery should NOT be undertaken when you are listening to these tones because your attention is shared between the two tasks. Tasks like gardening or sewing or cooking can be done while your brainwave entrainment music is playing.
Sound and light are the most popular methods to entrain the mind, yet there are a few other options in our toolbox. Using vibrational energy from sources such as magnets and electricity has been proven to help overcome addictions, depression, and even treat neurological disorders such as Parkinson’s. In this section, we cover these alternative forms of brainwave entrainment.
I appreciate your compliment on my article Henry. I’ve been using and reading up on isochronic tones and brainwave entrainment for many years, so it was just a case of trying to put a lot of what I’ve learnt into one article. I don’t have a great deal of knowledge or experience in using hypnosis and subliminals, so I’m afraid I wouldn’t be in a position to create something so extensive in reviewing them.
Isochronic tones have only been proven to have an effect while you are listening to them, that’s why you won’t find me claiming anywhere that there are potentially positive long-term effects. Once the tones stop, your brainwaves are no longer being stimulated by the sound and so they stop being in sync with the tone frequency. For you to think you are still feeling the effects after all this time and from such a short time listening to them, I think it may be linked to anxiety. I know that some people who are new to this type of thing can build up a strong feeling of anxiety, after worrying about the potential effects brought on by fear of the unknown. I suspect the problem may be psychological with you worrying about the potential effects and keep repeating the experience from memory in your head. When you keep going over the same thing in your head like that and worrying about it, it’s easy to then spot other potential side-effects like how your nostrils and body temp is feeling, then making links back to that experience and labelling that as the reason. I think the best way to overcome this is to realise that the side-effects you are mentioning are completely unrelated, so there is nothing to worry about. These tracks are literally listened to for millions of hours a month on YouTube across loads of channels. If the effects lasted for a long time people would just listen for 5 minutes and come back in a couple of weeks. But people keep coming back to listen because that’s the only way to feel the benefit and effects…while you are listening to them. If you are unable to stop thinking and worrying about this on our own, I recommend that you speak to your doctor about it or a specialist in dealing with anxiety issues. I hope that helps.
In a recent national survey, 44 percent of adults said stress had caused sleepless nights at least once in the previous month. All that tossing, turning and staring at the ceiling can leave you feeling tired and more stressed the next day. If you’re caught in this vicious cycle of anxiety and insomnia, there’s good news: Simple stress relief techniques can help you sleep better and feel calmer.