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

F. Holmes Atwater
(Revised July 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 willfully participate by listening to a
combination of multiplexed audio binaural beats
that are mixed with music, pink sound(2), and/or
surf and by focusing attentional processes. 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 be
associated with an electroencephalographic (EEG)
frequency-following response 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).
Binaural-beat stimulation, coupled with the effects
of the other procedures within the Hemi-Sync
process, appears to encourage access to altered
states of consciousness. The effectiveness of
Hemi-Sync in engendering state changes is
supported by the consistent reports of thousands
of Hemi-Sync users, as well as the documentation of
physiological changes associated with Hemi-Sync
use.

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 creativity, 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-known
autonomic effects of controlled breathing and
progressive relaxation and the psychology of
affirmations and visualizations. This
understanding also includes 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 have been described
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. 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. 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 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. 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 waveform 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)" (Owens & Atwater,
1995). This activity is conducted to the cortex
where it can be 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" (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).

Passively 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 ability of the listener to relax and
focus attention may contribute to binaural-beat
effectiveness in inducing state changes.
"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" (Owens & Atwater, 1995).
The perception of a binaural beat is, for example,
said to be heightened by the addition of white
noise to the carrier signal (Oster, 1973), so white
noise is often used as background. "Music,
relaxation exercises, guided imagery, and verbal
suggestion have all been used to enhance the
state-changing effects of the binaural beat"
(Owens & Atwater, 1995). Other practices such as
humming, toning, breathing exercises, 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. We are in the midst of a revolution
focusing on the study of consciousness (Owens,
1995). 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
Penfield's work, other researchers have reported
awareness in comatose patients (Hunt, 1995) and
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; Jevning,
Wallace, & Beidenbach, 1992; Wallace, 1986;
Mavromatis, 1991). These states are variously
referred to as medi- tative, 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
as a natural ability or as an acquired skill
(Sabourin, Cutcomb, Crawford, & Pribram, 1993).
More and more scientists are expressing doubts
about the neurologists' brain-mind model because
it fails to answer 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
mind-consciousness 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 and easily quantified. Contemporary
science likes things that can be measured and
quantified. The problem here lies in
oversimplification 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 relative proportions of EEG
frequencies. Stated another way, certain EEG
patterns have been historically associated with
specific states of consciousness. It is reasonable
to assume, given the current EEG literature, 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
and awareness is maintained, a unique state of
consciousness emerges. Practitioners of the
Hemi-Sync process call this state of hypnagogia
"mind awake/body asleep." 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). 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
unique 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 "hardwired" (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 physiological 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 brain function by enabling the user
to mediate cross-collosal 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 interfacing
with the brain) can be defined not only in terms of
brain-wave frequency ratios, 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.

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, the 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 of consciousness,
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).

The Monroe Institute has been studying altered
states of consciousness and developing Hemi-Sync
binaural beats for more than thirty years. The
process of developing effective stimuli relied
initially on the feedback of those experiencing
altered states associated with listening to
binaural beats, and more recently with the aid of
EEG technology. Originally, Robert Monroe tested
many subjects under laboratory conditions for
their responses to binaural-beat stimuli. 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. Certain combinations of
binaural beats were reported more effective than
other combinations, and more effective than
binaural beats of single frequencies.

Given the complexity of brain function and the
likelihood that the mixture of EEG frequencies
results from different generators localized in
different regions of the brain, it was theorized
that to entrain a particular state of
consciousness 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 may be the
complexity of the stimuli that makes the binaural
beats of the Hemi-Sync process so effective.
Theoretically, the heterodyned binaural beats
within these unique mixes entrain separate areas
of the brain to different frequencies, reliably
producing altered states with similar
characteristics.

It is tempting to speculate about a
neurophysiological model underlying the state of
consciousness labeled Focus 10 (mind awake/body
asleep). In Focus 10 a greater proportion of lower
frequency brain waves (theta and delta) have been
recorded in the EEG. The "body asleep" part of
Focus 10 may be tied to the increase in delta waves
associated with hyperpolarization of
thalamocortical cells (Steriade, McCormick, &
Sejnowski, 1993). The "mind awake" part of Focus 10
may be achieved by entraining a portion of the
hippocampus to a theta frequency. The subject's
exposure to these individual binaural beats is
timed, introducing the delta signals first and later
mixing in theta signals. This allows for a
dissolution of the psychophysiological
homeostasis and for changes in consciousness.
This Focus 10 Hemi-Sync binaural-beat signal
seems to have a soothing entrainment effect on the
limbic system (the brain's emotional center) as
evidenced by the many participants who report that
Focus 10 is a very pleasant experience.
Participants are said to have achieved Focus 10
mind-consciousness when a new condition of
hypnagogic homeostasis is established and they
become oblivious to the location of body
extremities (hands, feet, etc.), still without
losing consciousness (falling asleep). During this
state, participants are usually focused on
internal processes (imagery, etc.). Participants
return 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 brain-wave entrainment
effect. The Hemi-Sync process is safe and
effective and has a wide variety of applications
which include, but are not limited to:
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 beyond 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 nonverbal communication
or NVC.

6. The expressions "in" and "out-of-body" refer to
individual awareness. In the out-of-body
experience mind-consciousness does not separate
from the human tissue as in death. 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 be unable 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 subconscious activity (respiration,
heart beat, 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. Researchers
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. Some birds are ventriloquial and conceal their
true location by presenting a false sonic local.

11. Hemi-Sync is available to the public through
various audio-guidance learning systems.
Week-long programs are 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 excursion
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
more than two decades.

Hemi-Sync is a registered trademark of The Monroe
Institute