The effects are strongest while you are listening to the tones because your brainwaves are synchronized and tuned into the frequency range you desire at that time. After you've stopped listening the effects can still linger for a while afterwards. The timescale will vary from person to person and be affected by what you do after you've stopped listening.
When your mind is all over the place, organizing your thoughts into a quick to-do list can help transfer the burden from your brain to paper. But for some people, seeing a long list of tasks can increase stress. Miller has another idea: a “stressor and action” sheet. “Fold a piece of paper in half length wise, and on the left column write ‘stressor’ and on the right hand column write ‘action,’” she says. “You will find as you write down thoughtful action steps to the things that are stressing you out, you regain authority over circumstance.” These are the signs you’re more stressed than you realize.
Stress is a significant individual and public health problem that is associated with numerous physical and mental health concerns. It is estimated that between 75% and 90% of primary care physician visits are caused by stress-related illnesses (2). Cardiovascular disease, obesity, diabetes, depression, anxiety, immune system suppression, headaches, back and neck pain, and sleep problems are some of the health problems associated with stress (4,8). These conditions are some of the most burdensome health problems in the United States based on health care costs, the number of people affected, and the impact on individual lives. Extreme levels of stress were reported by 22% of respondents from the 2011 Stress in America™ survey, and 39% reported that their level of stress had increased during the past year (3). More than 80% of the survey respondents at the WorldatWork Conference in 2012 reported that stress moderately or significantly contributed to their health care costs (6).
Beating can also be heard between notes that are near to, but not exactly, a harmonic interval, due to some harmonic of the first note beating with a harmonic of the second note. For example, in the case of perfect fifth, the third harmonic (i.e. second overtone) of the bass note beats with the second harmonic (first overtone) of the other note. As well as with out-of tune notes, this can also happen with some correctly tuned equal temperament intervals, because of the differences between them and the corresponding just intonation intervals: see Harmonic series (music)#Harmonics and tuning.
Whenever we become very relaxed and the usual chatter of the mind slows down a little bit, if we remain aware and do not slip into sleep or unconsciousness, we begin to perceive things that we had not noticed before. This is slightly different than the issue of “expectations” discussed previously, although a relationship to them can develop which will be discussed below. These have to do with the fact that in our typical state of consciousness our mind is racing so fast and so loud, and our body is so engaged with activity and physical tension, that we are unaware of some subtle perceptions that are there all the while, but which get buried beneath all the physical and mental noise.
Cory Allen [b. 1982] is a composer and mastering engineer living in Austin, Texas. His work focuses on the cultivation of human perception with the intent of altering the listener's state of consciousness. Allen's music is deep, patient, meditative, highly-conceptual and often composed by implementing self-organizing structures, rule-based performances, set pitch classes and a wide variety of instruments.
Binaural beats were discovered in 1839 by a German experimenter, H. W. Dove. The human ability to "hear" binaural beats appears to be the result of evolutionary adaptation. Many evolved species can detect binaural beats because of their brain structure. The frequencies at which binaural beats can be detected change depending upon the size of the species' cranium. In the human, binaural beats can be detected when carrier waves are below approximately 1000 Hz (Oster, 1973). Below 1000 Hz the wave length of the signal is longer than the diameter of the human skull. Thus, signals below 1000 Hz curve around the skull by diffraction. The same effect can be observed with radio wave propagation. Lower-frequency (longer wave length) radio waves (such as AM radio) travel around the earth over and in between mountains and structures. Higher-frequency (shorter wave length) radio waves (such as FM radio, TV, and microwaves) travel in a straight line and can't curve around the earth. Mountains and structures block these high-frequency signals. Because frequencies below 1000 Hz curve around the skull, incoming signals below 1000 Hz are heard by both ears. But due to the distance between the ears, the brain "hears" the inputs from the ears as out of phase with each other. As the sound wave passes around the skull, each ear gets a different portion of the wave. It is this waveform phase difference that allows for accurate location of sounds below 1000 Hz(9). Audio direction finding at higher frequencies is less accurate than it is for frequencies below 1000 Hz. At 8000 Hz the pinna (external ear) becomes effective as an aid to localization. In summary it's the ability of the brain to detect a waveform phase difference is what enables it to perceive binaural beats.
“Chronic stress,” however, is not so easily resolved. This type of stress is associated more commonly with negative health concerns. Chronic stress results when there are constant multiple stressors or major life stressors present (4). Money, work, and the economy were the most commonly reported factors contributing to chronic stress in the American Psychological Association’s (APA) 2011 Stress in America™ survey (3). Additional significant stressors include relationships, family responsibilities, family and personal health problems, job stability, and personal safety (3). Major events, such as the death of a loved one, divorce, and moving also can produce chronic stress.
There are various reasons we seek this sort of validation. Many of us first try meditation to find relief from all sorts of different problems. Some seek relief from physical or emotional ailments; for solutions to personality shortcomings, such as a short temper or a tendency towards jealousy, etc. Some problems may be quite serious, even life threatening. Our search for relief may have been going on for a very long time without having found exactly what we were searching for.
All brainwave frequencies are useful and beneficial at certain times – there is no brainwave that is intrinsically better than another. However, by deliberately choosing to attain a particular brainwave state, a corresponding mental state can be brought about at the same time. For example, a working person who has been in an overly alert beta brainwave pattern for many hours can quickly shift their mind and body into a relaxed state by listening to a few minutes of brainwave entrainment music for inducing alpha or theta brainwaves.
^ Trost W. and Vuilleumier P., Rhythmic entrainment as a mechanism for emotion induction by music: a neurophysiological perspective. In The Emotional Power of Music: Multidisciplinary Perspectives on Musical Arousal, Expression, and Social Control, Cochrane T., Fantini B., and Scherer K. R., (Eds.), Oxford, UK: Oxford University Press; 2013, pp213–225.