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Dunnett’s Comp. (two-tailed) Difference P Q Critical q (.05)
---------------------------------------------------------------------------------------------
Mean Baselines - Mean Period 1 3.2829 2 1.66 1.98
Mean Baselines - Mean Period 2 5.2077 3 2.633 2.241 *
Mean Baselines - Mean Period 3 6.5251 5 3.299 2.471 *
Mean Baselines - Mean Period 4 6.0328 4 3.05 2.381 *
Mean Baselines - Mean Period 5 7.2465 6 3.664 2.55 *
Mean Baselines - Mean Period 6 8.7758 7 4.437 2.601 *
Comparisons marked with an asterisk “*” are significantly (p < .05) different.
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Figure 3. Changes in occipital-alpha EEG
Statistical analysis of the data also showed that the increases in the percentages of central delta (bipolar C3–C4) during
stimuli conditions were significant (individually, p < .05) during four of six stimulus periods compared to baselines (see below).
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Analysis Summary for Central Delta - Stimulus Condition
Mean s and standard deviations for percent central delta:
Baselines: mean = 18.4534 s. d. = 2.7744 n = 18
Period 1: mean = 21.1218 s. d. = 3.3948 n = 18
Period 2: mean = 21.457 s. d. = 3.5 n = 18
Period 3: mean = 25.1393 s. d. = 7.4027 n=1
Period 4: mean = 25.218 s. d. = 6.4961 n = 18
Period 5: mean = 24.7991 s. d. = 7.0691 n = 18
Period 6: mean = 25.1343 s. d. = 5.5444 n = 18
Analysis of Variance Table
Source -S.S.- -DF- -MS- -F- Approx. p
---------------------------------------------------------------------------------------------------------
Total 4,344.82 125
Treatment 788.73 6 131.46 4.4 < .001
Error 3,556.08 119 29.88
---------------------------------------------------------------------------------------------------------
Error term used for comparisons = 35.2 with 119 d. f.
Dunnett’s Comp. (two-tailed) Difference P Q Critical q (.05)
---------------------------------------------------------------------------------------------------------
Mean Baselines - Mean Period 1 2.6685 2 1.464 1.98
Mean Baselines - Mean Period 2 3.0036 3 1.648 2.241
Mean Baselines - Mean Period 3 6.6859 6 3.669 2.55 *
Mean Baselines - Mean Period 4 6.7646 7 3.712 2.601 *
Mean Baselines - Mean Period 5 6.3358 4 3.477 2.381 *
Mean Baselines - Mean Period 6 6.681 5 3.666 2.471 *
Comparisons marked with an asterisk “*” are significantly (p < .05) different.
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Figure 4. Changes in central-delta EEG
The results of this first study significantly distinguished brainwave activity during the stimulus periods from the
baseline recordings both with increased central-delta EEG levels and decreased occipital-alpha EEG levels. Decreases
in alpha amplitudes coupled with increasing delta activity indicate reduced cortical arousal (Berger et al. 1968). The
mounting changes over the course of the stimuli suggest a deepening trend of progressive relaxation and falling
asleep. Some so-called altered states of consciousness can also be associated with increased delta (Empson 1986) and a
suppression of occipital alpha.
A basic question raised by this study was the role of binaural-beat stimulation in solely or directly causing the state
changes observed. Several of the subjects had considerable previous experience with binaural-beat audio recordings. It
may be that the subjects in this study were naturally adept at altering levels of arousal or that they had acquired this ability
through repeated practice. Additionally, the deepening trend over time suggests the need to take naturally occurring,
progressive state changes associated with falling asleep into consideration.
Second Study
To address these concerns a second study measured the changes in ongoing brainwave activity during a placebo
stimulus (without binaural beats). This study examined the degree to which monotonous tones in the same environment as
the first study influenced ongoing central-delta and occipital-alpha brainwave activity.
Hypothesis
Listening to monotonous tones for several minutes will result in habituation of the stimuli, a slowing of ongoing brain-
wave activity (increased delta and decreased alpha), and a progressive state of relaxation.
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Method
The second study also included 20 volunteer subjects. The subjects remained supine in a darkened, sound-attenuating
chamber as in the first study. Subjects reported normal hearing. None of the subjects reported a history of mental,
emotional, or nervous-system disorders.
The placebo stimuli consisted of the same mixed sinusoidal tones changing over a period of 45 minutes used with
the first study, with the exception that they did not produce binaural beating. The stimuli were presented with stereo
earphones at 40 dB above subjective threshold. The volunteer subjects first experienced a no-stimulus baseline condition
during which a 90-second EEG recording was taken. Next, each subject listened to the same 45-minute sequence of
changing tones during which six 90-second EEG recordings were taken at regular intervals. To reduce the influence
of expectation, subjects were again blind as to the character of the tones. Finally, during a no-stimulus post-baseline
condition, a 90-second EEG recording was made.
Subjects were connected to a 24-channel digitizing EEG computer in the same manner as in the first study. As in the
first study, a sampling rate of 256 samples per second was used, which provided for an EEG frequency response of 1-64
Hz, a frequency resolution of 1 Hz, and a temporal resolution of one second.
The placebo tones cross-faded smoothly from one to another during the 45-minute protocol. Detailed below are the
audio stimuli experienced by the subjects during the designated EEG recording periods:
Left-Ear Right-Ear Volume EEG Recording Periods
50 Hz 50 Hz 40% First @ 3 Minutes
100 Hz 100 Hz 32%
200 Hz 200 Hz 28%
50 Hz 50 Hz 40% Second @ 8 Minutes
100 Hz 100 Hz 32%
200 Hz 200 Hz 28%
50 Hz 50 Hz 29% Third @ 14 Minutes
75 Hz 75 Hz 26%
100 Hz 100 Hz 24%
200 Hz 200 Hz 21%
50 Hz 50 Hz 20% Fourth @ 22 Minutes
100 Hz 100 Hz 18%
125 Hz 125 Hz 25%
200 Hz 200 Hz 15%
200 Hz 200 Hz 22%
50 Hz 50 Hz 24% Fifth @ 30 Minutes
100 Hz 100 Hz 23%
200 Hz 200 Hz 35%
325 Hz 325 Hz 12%
525 Hz 525 Hz 6%
50 Hz 50 Hz 29% Sixth @ 38 Minutes
100 Hz 100 Hz 28%
200 Hz 200 Hz 36%
850 Hz 850 Hz 4%
1,375 Hz 1,375 Hz 3%
Results
The data on two subjects were rejected due to movement artifact, leaving 18 subjects as in the first study. A multiple
comparison procedure following a one-way ANOVA (Dunnett’s test) comparing the combined baselines as a control mean
with the placebo stimuli periods showed nonsignificant reductions in the percentages of occipital alpha (bipolar O1–O2)
during stimuli conditions compared to baselines (see below).
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Analysis Summary for Occipital Alpha - Placebo Condition
Means and standard deviations for percent occipital alpha:
Baselines: mean = 30.3427 s. d. = 9.7672 n = 18
Period 1: mean = 29.8544 s. d. = 9.2752 n = 18
Period 2: mean = 27.7227 s. d. = 8.0999 n = 18
Period 3: mean = 26.3955 s. d. = 7.771 n = 18
Period 4: mean = 28.6144 s. d. = 8.6961 n = 18
Period 5: mean = 24.5212 s. d. = 6.3118 n = 18
Period 6: mean = 27.5927 s. d. = 8.7169 n = 18
Analysis of Variance Table
Source -S.S.- -DF- -MS- -F- Approx. p
----------------------------------------------------------------------------------------------------
Total 8914.46 125
Treatment 433.67 6 72.28 1.01 0.4194
Error 8480.78 119 71.2
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Error term used for comparisons = 71.27 with 119 d. f.
Dunnett’s Comp. (2-tailed) Difference P Q Critical q (.05)
----------------------------------------------------------------------------------------------------------
Mean Baselines - Mean Period 1 0.4883 2 .174 1.98
Mean Baselines - Mean Period 2 2.62 4 .931 2.381
Mean Baselines - Mean Period 3 3.9472 6 1.403 2.55
Mean Baselines - Mean Period 4 1.7283 3 .614 2.241
Mean Baselines - Mean Period 5 5.8215 7 2.069 2.601
Mean Baselines - Mean Period 6 2.75 5 .977 2.471
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Figure 5. Occipital-alpha EEG
Statistical analysis of the data also showed the nonsignificant increases in the percentages of central delta
(bipolar C3–C4) during stimuli conditions compared to baselines (see below).
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Analysis Summary for Central Delta - Placebo Condition
Means and standard deviations for percent central delta:
Baselines: mean = 18.1997 s. d. = 4.0204 n = 18
Period 1: mean = 18.5893 s. d. = 4.234 n = 18
Period 2: mean = 20.298 s. d. = 3.9881 n = 18
Period 3: mean = 21.0204 s. d. = 4.0122 n = 18
Period 4: mean = 21.6606 s. d. = 5.1337 n = 18
Period 5: mean = 21.8038 s. d. = 4.334 n = 18
Period 6: mean = 19.5615 s. d. = 4.449 n = 18
Analysis of Variance Table
Source -S.S.- -DF- -MS- -F- Approx. p
-----------------------------------------------------------------------------------------------------------
Total 2450.28 125
Treatment 222.86 6 37.14 1.98 0.0732
Error 2227.42 119 18.72
----------------------------------------------------------------------------------------------------------
Error term used for comparisons = 18.72 with 119 d. f.
Dunnett’s Comp. (two-tailed) Difference P Q Critical q (.05)
-----------------------------------------------------------------------------------------------------------
Mean Baselines - Mean Period 1 0.3895 2 .27 1.98
Mean Baselines - Mean Period 2 2.0982 4 1.455 2.381
Mean Baselines - Mean Period 3 2.8207 5 1.956 2.471
Mean Baselines - Mean Period 4 3.4609 6 2.4 2.55
Mean Baselines - Mean Period 5 3.604 7 2.499 2.601
Mean Baselines - Mean Period 6 1.3618 3 .944 2.241
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Figure 6. Central-delta EEG
The results of this second study did not significantly distinguish occipital-alpha and central-delta brain-wave activity
during the placebo stimulus periods from the baselines. As set forth in the hypothesis of this placebo study, the observed
decreases in alpha amplitudes coupled with increasing delta activity were expected as a reaction to listening to monotonous
tones. These changes, however, were not statistically significant—meaning that they could be expected to have happened
by chance alone.
Discussion
These studies appear to demonstrate that the binaural beat has a direct effect on brain-wave activity. Such a direct
effect would involve the interaction of binaural-beat stimulation with the basic rest-activity cycle, with other sensory
stimulation, and with “higher order” memory or attentional processes under the scrutiny of the reticular formation. All of
these systems cooperate to maintain homeostasis and optimal performance. Natural state changing mechanisms (Steriade,
McCormick, and Sejnowski 1993), ultradian rhythms, individual differences, prior experience, and beliefs may all
contribute to the effects of and response to binaural-beat stimulation as they do with nearly all other behaviors.
Newman (1997a,b) and references therein describe the extended reticular-thalamic activating system and convincingly
argue that this “conscious system” is responsible for modifying generalized levels of arousal as well as individual explicit patterns
of arousal. Newman (1997a) writes, “This extended reticular-thalamic activating system (ERTAS) has been increasingly
implicated in a variety of functions associated with consciousness, including: orienting to salient events in the outer world;
dream (REM) sleep; the polymodal integration of sensory processes in the cortex (binding); selective attention and volition.”
It may be that rhythmic sound patterns affect overall cortical levels of arousal by providing frequency information from the