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]
It may be that you had the volume too loud, but I would expect you to hear the effects of that straight after you’ve stopped listening, not on a day you haven’t used them. It might be something similar to muscle memory, where you suddenly remembered the sound and sensations it gives you as if you were hearing it again. I don’t know how long you’ve been using this type of thing for, but maybe it’s something that will settle down and disappear once you become more accustomed to the sound.
There's no doubt that brainwave entrainment audio is a great technology for anyone who is interested in encouraging altered states of consciousness and it certainly can help people to reach deeper states of relaxation than they might normally have access to. I myself will often listen to brainwave entrainment music in order to enhance my practice of meditation. But let’s keep a balanced perspective, put all the marketing hype to one side for a moment and acknowledge that there is no brainwave entrainment technology in this world that can make you meditate like a Zen monk “at the touch of a button”, despite what some might like you to believe. The mind is NOT a machine. It moves through various states of consciousness in an organic way and at a natural pace. We certainly can guide and accelerate that process with the use of brainwave entrainment audio, but we cannot control it with the same sort of specificity and immediacy as you might control the speed of the car you drive.
... These factors may be the specific frequency of BB; the targeted population-because it is known that older people have different quality of brainwave activity than, e.g., youngsters (Bazanova & Aftanas, 2008;Clark et al., 2004), and the tests used to detect the possible changes in working memory capacity. Based on the research showing a positive impact of alpha-range BB on cognitive functioning, specifically attention, auditory sequential memory, working memory, working memory storage, reasoning ability, cognitive processing and hemispheric synchronization, (Carter & Russell, 1993;Cruceanu & Rotarescu, 2013;Foster, 1990;Kennerly, 1994;McMurray, 2006) as well as on the wealth of research documenting the important role of alpha brain wave activity on vigilance, in-hibitory processes, attention, filtering out irrelevant information working memory, the visuo-spatial component of working memory, perceptual abilities and information processing speed (Braboszcz & Delorme, 2011;Clark et al., 2004;Engle et al., 1999a;Freunberger et al., 2011;Klimesch et al., 2007;Lachat et al., 2012;Oprisan, 2004;Palva & Palva, 2007;Rihs et al., 2007;Sauseng et al., 2009;Tuladhar et al., 2007;VanRullen & Koch, 2003), we believe that BB of a frequency that corresponds to the alpha range of brain activity has a temporary effect on working memory capacity. In our study, subjects were exposed to 9.55 Hz BB stimulation while we measured their working memory capacity through the Automated Operation Span Task (AOSPAN). ...

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.
Brainwaves are the collective electrical signal of millions of neurons working together in a living brain, producing our sense of alertness – or lack thereof - and producing our experience of reality. As brainwaves change, so does our perception of the world and our inner perception of ourselves. By learning to control our brainwaves, we can achieve specific, desirable mental states, such as feeling more relaxed, less anxious, more creative, more focused, or sleepier.
To use your senses to quickly relieve stress, you first need to identify the sensory experiences that work best for you. This can require some experimentation. As you employ different senses, note how quickly your stress levels drop. And be as precise as possible. What is the specific kind of sound or type of movement that affects you the most? For example, if you’re a music lover, listen to many different artists and types of music until you find the song that instantly lifts and relaxes you.
There is no single relaxation technique that is best for everyone. The right relaxation technique is the one that resonates with you, fits your lifestyle, and is able to focus your mind and interrupt your everyday thoughts to elicit the relaxation response. You may even find that alternating or combining different techniques provides the best results. How you react to stress may also influence the relaxation technique that works best for you:
Women worry more than men do. A study of 166 married couples who kept stress diaries for six weeks found that women feel stress more frequently than men because women tend to worry in a more global way. Whereas a man might fret about something actual and specific—such as the fact that he's just been passed over for a promotion—a woman will tend to worry abstractly about her job, her weight, plus the well-being of every member of her extended family. Keep your anxiety focused on real, immediate issues, and tune out imagined ones or those over which you have zero control, and you'll automatically reduce stress overload.
Robert Monroe, a radio producer and executive published a popular book called Journeys Out of the Body about his out-of-body experiences when using brainwave entrainment. He later founded an original brainwave entrainment audio company, Hemi Sync. In 1981, the book Mega Brain by Michael Hutchison brought brainwave entrainment information, techniques, and terminology into the popular press.
Other entrainment methods sometimes used include autopan modulation that moves sound in an 180º arc to create a desired tone. Harmonic box entrainment, invented by James Mann, uses a layering of binaural and monaural tones that alternate between ears, requiring headphones. Sound modulation and filtering, amplitude modulation, and pitch panning use diverse sounds to create rhythmic pulses matched to the desired brainwave frequency. 
Binaural beats are created from two different continuous tones, which when sent separately to each ear create a single beat inside your head. Isochronic tones are basically a single tone which is switched on and off at regular intervals. Imagine a single continuous tone playing on a stereo system and you’ve got your hand on the volume switch. Then once per second, you turn the volume off for half a second and keep doing that every second. For half a second the volume is off, for the other half a beat waveform is formed. The beat is cycling once per second per second, i.e. at a rate of 1Hz.

The Frequency following response (FFR), also referred to as Frequency Following Potential (FFP), is a specific response to hearing sound and music, by which neural oscillations adjust their frequency to match the rhythm of auditory stimuli. The use of sound with intent to influence cortical brainwave frequency is called auditory driving,[39][40] by which frequency of neural oscillation is 'driven' to entrain with that of the rhythm of a sound source.[41][42]
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