THE MONROE INSTITUTE'S HEMI-SYNC(R) PROCESS
A THEORETICAL PERSPECTIVE

F. Holmes Atwater (Revised June, 1995)

Introduction

Hemi-Sync is a patented(1) auditory-guidance system developed by
Robert A. Monroe which provides access to beneficial states of
consciousness. The trademarked term Hemi-Sync signifies a
process, a procedure in which individuals listen to a
combination of multiplexed audio binaural beats which are mixed
with music, pink sound(2) and/or surf. In most cases the
Hemi-Sync process also includes breathing exercises, guided
relaxation, affirmation, and visualization. The binaural-beat
element of the Hemi-Sync process appears to produce an
electroencephalographic (EEG) frequency-following response (FFR)
in the brain(3). Many studies have demonstrated the presence of
a frequency-following response to auditory stimuli, recorded at
the vertex of the human brain (top of the head). This EEG
activity was termed "frequency-following response" because its
period corresponds to the fundamental frequency of the stimulus
(Smith, Marsh, & Brown, 1975). The presence of stimuli-specific
EEG activity as measured by the FFR gives rise to the
probability of a resonant entrainment of brain waves. It is this
entrainment coupled with the effects of the other procedures
within the Hemi-Sync process that appears to provide individuals
access to altered states of consciousness.

The reported uses of Hemi-Sync range from relaxation,
meditation, stress reduction, pain management, improved sleep
quality, health care (Carter, 1993), and enriched learning
environments to enhanced intuition, remote viewing(4)
(McMoneagle, 1993), telepathy(5), and out-of-body experience(6).
An understanding of the Hemi-Sync technology involves the
well-understood autonomic effects of controlled breathing and
progressive relaxation, the psychology of affirmations and
visualizations, as well as the physics of resonant entrainment,
brain waves and their relationship to the behavioral psychology
of consciousness, and the physiology of the brain. For the
purposes of this paper, discussion is limited to the latter
portions of this understanding as the former are easily
researched elsewhere.

The Physics of Resonant Entrainment

Resonant entrainment of oscillating systems is a well-understood
principle within the physical sciences. If a tuning fork
designed to produce a frequency of 440 Hz is struck (causing it
to oscillate) and then brought into the vicinity of another 440
Hz tuning fork, the second tuning fork will begin to oscillate.
The first tuning fork is said to have entrained the second or
caused it to resonate. The physics of entrainment apply to
biosystems as well. What is of interest here are the
electromagnetic brain waves. The electrochemical activity of the
brain results in the production of electromagnetic wave forms
which can be objectively measured with sensitive equipment.
Brain waves change frequencies based on neural activity within
the brain. Because neural activity is electrochemical, brain
function can be modified through the introduction of specific
chemicals (drugs), by altering the brain's electromagnetic
environment through induction(7), or through resonant
entrainment techniques. Caffeine, nicotine, and alcohol are
drugs; whereas heterodyning radio and microwave frequencies all
around us and the binaural beats of the Hemi-Sync process are
entrainment environments.

Hemi-Sync's Binaural Beats and The Physiology of the Brain

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(8) 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 wave-form 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. Virtually all
animal sounds are below 1000 Hz. It is easy to imagine why
animals developed the ability to accurately detect the location
of each others' sounds(10). The relevant issue here, however, is
that it is this innate ability of the brain to detect a
wave-form phase difference that enables it to perceive binaural
beats.

When signals of two different frequencies are presented, one to
each ear, the brain detects phase differences between these
signals. Under natural circumstances a detected phase difference
would provide directional information. The brain processes this
anomalous information differently when these phase differences
are heard with stereo headphones or speakers. A perceptual
integration of the two signals takes place, producing the
sensation of a third "beat" frequency. The difference between
the signals waxes and wanes as the two different input
frequencies mesh in and out of phase. As a result of these
constantly increasing and decreasing differences, an
amplitude-modulated standing wave -- the binaural beat -- is
heard. The binaural beat is perceived as a fluctuating rhythm at
the frequency of the difference between the two auditory inputs.
Evidence suggests that the binaural beats are generated in the
brainstem's superior olivary nucleus, the first site of
contralateral integration in the auditory system (Oster, 1973).
Studies also suggest that the frequency-following response
originates from the inferior colliculus (Smith, Marsh, & Brown,
1975). This activity is volume conducted to the cortex where it
is readily recorded by scalp electrodes.

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 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. 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), or 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).

Passive listening to binaural beats may not spontaneously propel
you into an altered state of consciousness. Remember, the
Hemi-Sync process includes a number of procedures; binaural
beats are only one element. We all maintain a
psychophysiological momentum, a homeostasis which resists the
influence of the binaural beats. These homeostatic environments
are generally controlled by life situations as well as by acts
of will, both conscious and subconscious, and must be overcome
to experience shifts in consciousness. One's subjective
experience in response to binaural-beat stimulation may also be
influenced by a number of mediating factors. For example, the
willingness and skill of the listener in relaxing and focusing
attention on the binaural beats may contribute to their
effectiveness in inducing state changes due to the perceptual
nature of the binaural beats. Ultradian rhythms in the nervous
system are characterized by periodic changes in arousal and
states of consciousness (Rossi, 1986; Shannahoff-Khalsa, 1991;
Webb & Dube, 1981). These naturally occurring shifts may
underlie the anecdotal reports of fluctuations in the
effectiveness of binaural beats. External factors are also
thought to play roles in mediating the effects of binaural
beats. For example, the perception of a binaural beat is
heightened by the addition of white noise to the carrier signal
(Oster, 1973), so white noise is often used in the background of
the binaural-beat stimulation. Music, relaxation exercises,
guided imagery, and verbal suggestion have all been used to
enhance the state-changing effects of the binaural beat. Other
practices such as humming (mantras; resonant tuning), autogenic
training, and/or biofeedback can also be used to interrupt the
homeostasis of resistant subjects (Tart, 1975).

Brain Waves and Consciousness

Controversies concerning the brain, mind, and consciousness have
existed since the early Greek philosophers argued about the
nature of the mind-body relationship, and none of these disputes
has been resolved. Modern neurologists have located the mind in
the brain and have said that consciousness is the result of
electrochemical neurological activity. There are, however,
growing observations to the contrary. There is no
neurophysiological research which conclusively shows that the
higher levels of mind (intuition, insight, creativity,
imagination, understanding, thought, reasoning, intent,
decision, knowing, will, spirit, or soul) are located in brain
tissue (Hunt, 1995). A resolution to the controversies
surrounding the higher mind and consciousness and the mind-body
problem in general may need to involve an epistemological shift
to include extra-rational ways of knowing (de Quincey, 1994) and
cannot be comprehended by neurochemical brain studies alone.
Penfield, an eminent contemporary neurophysiologist, found that
the human mind continued to work in spite of the brain's reduced
activity under anesthesia. Brain waves were nearly absent while
the mind was just as active as in the waking state. The only
difference was in the content of the conscious experience.
Following on Penfield's work, numerous other researchers have
discovered total and acute awareness in comatose patients (Hunt,
1995). There is a growing body of evidence which suggests that
reduced cortical arousal while maintaining conscious awareness
is possible (Fischer, 1971; West 1980; Delmonte, 1984; Goleman
1988; Jevnig, Wallace, & Beidebach, 1992; Wallace, 1986;
Mavromatis, 1991), with these states variously referred to as
meditative, trance, altered, hypnagogic, hypnotic, and twilight
learning states (Budzynski, 1986). Broadly defined, the various
forms of altered states rest on the maintenance of conscious
awareness in a physiologically reduced state of arousal marked
by parasympathetic dominance (Mavromatis, 1991). Recent
physiological studies of highly hypnotizable subjects and adept
meditators indicate that maintaining awareness with reduced
cortical arousal is indeed possible in selected individuals with
this natural ability or acquired skill (Sabourin, Cutcomb,
Crawford, & Pribram, 1993). More and more scientists are
expressing doubts about the neurologists' brain-mind model
because it leaves unanswered so many questions about our
ordinary experiences, as well as evading our mystical and
spiritual ones. The scientific evidence supporting the
phenomenon of remote viewing alone is sufficient to show that
mindconsciousness is not a local phenomenon (McMoneagle, 1993).

If mind-consciousness is not the brain, why then does science
relate states of consciousness and mental functioning to brain
wave frequencies? And why does the Hemi-Sync process include a
binaural-beat technology which has the potential to alter brain
waves? The first question can be answered in terms of
instrumentation. There is no objective way to measure mind or
consciousness with an instrument. Mind-consciousness appears to
be a field phenomenon which interfaces with the body and the
neurological structures of the brain (Hunt, 1995). One cannot
measure this field directly with current instrumentation. On the
other hand, the electrical potentials of brain waves can be
measured directly and easily quantified. Contemporary science
likes things that can be measured and quantified. The problem
here lies in the over-simplification of the observations. EEG
patterns measured on the cortex are the result of
electroneurological activity of the brain. But the brain's
electroneurological activity is not mind-consciousness. EEG
measurements then are only an indirect means of assessing the
mind-consciousness interface with the neurological structures of
the brain. As crude as this may seem, the EEG has been a
reliable way for researchers to estimate states of consciousness
based on the coincidence of EEG patterns. Stated another way,
certain EEG patterns have been historically related to specific
states of consciousness. It is reasonable to assume from this
historical data that if a specific EEG pattern emerges it is
probably accompanied by a particular state of consciousness.

The second question raised in the above paragraph requires a
more complex explanation. The Hemi-Sync process includes the
powerful binaural-beat technology because altering the
electrochemical environment of the brain allows
mind-consciousness to have  different experiences. When the
brain is entrained to lower frequencies, mind-consciousness is
freed to be aware of the realms beyond the physical senses of
the body. Practitioners of the Hemi-Sync process call this state
of hypnagogia "mind awake/body asleep." Slightly higher-frequency
entrainment can lead to hypersuggestive states of consciousness.
Still higher-frequency entrainment allows mind-consciousness to
experience an enhanced interface with the brain resulting in
improved task oriented performance. In a way, brain waves
represent the electrochemical environment defining the reality
of which mind-consciousness is aware and experiences. 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 immediate socio-environmental
surroundings. (Some psychologists would call these changes in
ego states, or subpersonalities.) As mentioned before, states of
consciousness are subject to other influences as well. Such
things as drugs and sunspots can alter states of consciousness.
Additionally, all life forms appear to be subject to 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). The Hemi-Sync process offers access to a wide
variety of altered-state experiences.

Beyond the Basics

The term Hemi-Sync was chosen because many of the states of
consciousness available through this technology have been
identified as presenting hemispherically-synchronized brain-wave
frequencies. Although synchronized brain waves have long been
associated with meditative and hypnagogic states, the Hemi-Sync
process may be unique in its ability to induce and improve such
states of consciousness. The reason for this is physiological.
Each ear is "hard-wired" (so to speak) to both hemispheres of
the brain (Rosenzweig, 1961). Each hemisphere has its own
olivary nucleus (sound-processing center) which receives signals
from each ear. In keeping with this physiologi cal structure,
when a binaural beat is perceived there are actually two
standing waves of equal amplitude and frequency present, one in
each hemisphere. So, there are two separate standing waves
entraining portions of each hemisphere to the same frequency.
The unique binaural beats of the Hemi-Sync process appear to
contribute to the hemispheric synchronization evidenced in
meditative and hypnagogic states of consciousness. Hemi-Sync's
binaural beats can also enhance the effectiveness of the brain
by enabling the user to mediate cross-callosal connectivity at
designated brain-wave frequencies.

The two cerebral hemispheres of the brain are like two separate
information processing modules. Both are complex cognitive
systems; both process information independently and in parallel;
and their interaction is neither arbitrary nor continuous
(Zaidel, 1985). Because of this, states of consciousness
(mind-consciousness interface with the brain) can be defined not
only in terms of brain-wave frequency, but also in terms of
hemispheric specialization and/or interaction. Some desired
states of consciousness may require facile inter-hemispheric
integration, while others may call for a unique hemispheric
processing style. An individual's cognitive repertoire and,
therefore, his ability to perceive reality and deal with the
everyday world, is subject to his ability to experience various
states of consciousness. The Hemi-Sync process provides the
tools for individuals to expand their ability to experience a
wide range of mind-consciousness states.

The complexities of an effective Hemi-Sync binaural beat are
amazing. Each state of consciousness is not represented by one
simple brain wave. Each state of consciousness involves a milieu
of inner-mixing wave forms. The reason for this lies in the
structure of the brain itself. Not only is the brain divided
horizontally into hemispheres, it is also divided vertically
into the cerebellum, the thalamus, the limbic system, and the
cerebral cortex.

The cerebral cortex is further divided into such functional
areas as the frontal lobes, the parietal lobes, temporal lobes,
and the occipital lobes. There are, of course, many other
subdivisions of the brain which have not been mentioned. The
critical point is that for each discrete state,
mind-consciousness interfaces with each area of the brain and
each area resonates at a specific brain-wave frequency unique to
that interface because it performs a localized function (Luria,
1970). To entrain a particular state of consciousness then, one
must identify these complex wave forms and mimic them through
the use of a number of multiplexed carrier signals generating
heterodyned binaural beats. It is this complex stimuli that
makes the binaural beats of the Hemi-Sync process so effective.

The Monroe Institute has been identifying these states of
consciousness and developing Hemi-Sync binaural beats for over
thirty years. The process of developing effective stimuli has
been as complex as the function of the brain itself. Today,
computerized EEGs aid in the development of improved Hemi-Sync
technology at The Monroe Institute. Originally, Robert Monroe
tested many subjects under laboratory conditions for their
responses to binaural-beat stimulus. Records were kept as to the
effect each binaural-beat frequency had on these subjects. Then
binaural beats were mixed and records were again kept on the
subjects' responses. After months (in some cases, years), test
results began to show population-wide similar responses to
specific mixes of binaural beats. The heterodyned binaural beats
within these unique mixes entrained separate areas of the brain
to different frequencies, effectively producing discrete states
by allowing unique mind-consciousness interfacing with these
areas of the brain.

In the case of the state of consciousness labeled Focus 10 (mind
awake/body asleep), the cerebellum, which works below the level
of consciousness and deals with muscles and body functions, must
be entrained to a delta frequency. Under these conditions
(presumably a delta brain wave within the cerebellum) the body
is deeply relaxed or asleep. The "mind awake" part of Focus 10
is achieved by entraining a portion of the cerebral cortex to a
theta frequency. The subject's exposure to these individual
binaural beats is timed, introducing the delta cerebellum
signals first and later mixing in theta cerebral cortex signals.
This allows for a disintegration of the psychophysiological
homeostasis and the adaptation of the mind-consciousness
interface. This Focus 10 Hemi-Sync binaural-beat signal also
seems to have a soothing entrainment effect on the limbic system
(the brain's emotional center) as evidenced by the many subjects
who report that Focus 10 is a very pleasant experience. A
subject is said to have achieved Focus 10 mind-consciousness
when a new condition of hypnagogic homeostasis is established
and the subject becomes oblivious to the location of body
extremities (hands, feet, etc.), still without losing
consciousness (falling asleep). The subject returns easily to
full physical-waking consciousness when the Focus 10
binaural-beat signal is turned off.

Summary

The Hemi-Sync auditory-guidance process provides access to many
beneficial mind-consciousness states. This process is a unique
combination of well-understood inductive techniques with the
addition of a refined binaural-beat technology which appears to
have a brainwave entrainment effect. The Hemi-Sync process is
safe and effective and has a wide variety of applications which
include such things as relaxation, meditation, intuition
development, enriched learning, improved sleep, wellness, and
the exploration of expanded mind-consciousness states(11).

Footnotes

1. a. Patent Number: 3884218; Issue Year: 1975; State/Country:
VA; Marketed as: Hemi-Sync; Inventor: Robert A. Monroe; Title:
Method of Inducing and Maintaining Various Stages of Sleep in
the Human Being.
   b. Patent Number: 5213562; Issue Year: 1993;
State/Country: VA; Marketed as: Hemi-Sync; Inventor: Robert A.
Monroe; Title: Method of Inducing Mental, Emotional and Physical
States of Consciousness, Including Specific Mental Activity, in
Human Beings.
   c. Patent Number: 5356368; Issue Year: 1994;
State/Country: VA; Marketed as: Hemi-Sync; Inventor: Robert A.
Monroe; Title: Method of Inducing Desired States of
Consciousness.

2. Pink sound is "white noise" (like the hiss sound from a
television after a station has stopped transmitting) which has
been equalized for human hearing. Lower-frequency components
have been amplified and higher-frequency components reduced to
create a more pleasing natural sound.

3. A frequency-following response to a binaural beat has been
demonstrated in the context of audiometric research (Hink,
Kodera, Yamada, Kaga, & Suzuki, 1980).

4. Remote viewing is described as an ability to perceive
locations remote in time or space by mental means alone. Remote
viewers can describe and sketch locations and events out of the
range of the usual sensory input.

5. Telepathy is commonly referred to as direct mind-to-mind
communication without the aid of conventional external sensory
input. Robert Monroe referred to this as non-verbal
communication or NVC.

6. The expressions "in" and "out-of-body" refer to individual
awareness. With the out-of-body experience mind-consciousness
does not separate from the human tissue as in death. In the
physical world one's mind is always experienced as being either
in or out of the body. It depends on where awareness is focused.
Being out-of-body simply means that there is no direct
connection to certain material levels of consciousness including
the normally unconscious activities of breathing and heart
function which continue without your attention. Being
out-of-body is a consciousness experience with a shift of
mind-consciousness field energy and locale. Some enjoy this
shift. Others become frightened that they may get lost and not
be able to find their way back to their bodies. If you believe
that the mind is in the brain, and you experience what you
believe is out-of-body awareness, it is easy to feel that you
are too far from the "gas station" and that you can get
stranded. But the mind is not the brain so there is no reason to
fear. If you know you are "out" you can always get back because
there is some normally unconscious awareness (respiration, blood
flow, etc.) on the brain-material level to tether you back
(Hunt, 1995).

7. Sunspots alter the earth's magnetic environment and these
environmental changes are believed to alter brain-wave and other
bioelectrical patterns through the mechanism of induction.
Research ers have induced EEG changes using magnetic fields
directed at the head.

8. Electronically produced binaural beats can be "heard" when
audio tones of slightly different frequencies are presented one to
each ear. These audio tones are referred to as "carriers" of the
binaural beats.

9. In the case of signals above 1000 Hz the skull blocks the
signal from the lee-side ear. The source of the sound is then
determined by the brain to be in the general direction of the
loud noise, there being less noise heard by the lee-side ear.

10. As an interesting alternative, some birds are ventriloquial.
They produce bird song which conceals their true location by
presenting a false sonic local through wave-form phase
modulation.

11. Hemi-Sync has been made available to the public through the
development of various learning systems. There are residential
weeklong programs conducted at The Monroe Institute in Virginia.
There are also audio cassette tapes and CDs for use in the home,
clinical, or educational settings.

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About the Author

F. Holmes (Skip) Atwater works in the lab at The Monroe
Institute. He is an experienced mind-consciousness voyager and
has contributed to the evolution of the Hemi-Sync process and
the Institute since 1977. In September 1988 he initiated the now
ongoing psychophysiological research at the Institute. Skip also
monitors personalized mind-consciousness excursions sessions
(voyages into the realms of consciousness using Hemi-Sync
technology) conducted in the lab's isolation booth. Skip, a
retired military officer, has been a college instructor, author,
scientific investigator, and human behavioral engineer
specializing in the design and application of techniques for
cultivating propitious states of consciousness for over two
decades. He received a B. S. degree from the University of
Nebraska and completed his graduate coursework in counseling
psychology at the University of Northern Colorado.

Hemi-Sync is a registered trademark of The Monroe Institute

(C) 1995 The Monroe Institute