Binaural Beats: A Short Introduction

Copyright © 2010 by Dr. Brian Cullen
All over the Internet, there are claims that binaural beats are beneficial in some way, and they are often included as a background in hypnosis or relaxation audio programs. Like many claims, this is one that is worth examining a little more closely to see if it rests upon a solid foundation of research. This article does not attempt to examine the research in detail, but provides a brief introduction to binaural beats.

What are binaural beats?

The Webster-Merriam dictionary defines binaural as:

of, relating to, or involving two or both ears

Although this definition tells us that both ears are involved, binaural beats are not simply a stereo rhythm pattern as the name might indicate. Beats is a physical phenomenon that occurs when two very similar waves interfere with one another. These can be waves of sound, light, or a physical medium such as water, but for this article we are interested in beats resulting from the interference of sound waves. The Encyclopaedia Brittanica describes the simplest case of beats:

… beats result when two sinusoidal sound waves of equal amplitude and very nearly equal frequencies mix. The frequency of the resulting sound (F) would be the average of the two original frequencies (f₁ and f₂):

The amplitude or intensity of the combined signal would rise and fall at a rate (f_b) equal to the difference between the two original frequencies,

where f₁ is greater than f₂.

In other words, a new frequency is perceived which is equal to the difference between the two original frequencies. So, for example, if a 320 Hz sine wave is played into the right ear and a 330Hz one into the left ear, the brain perceives a beat frequency of 10 Hz. This is an interesting phenomenon because normal human hearing extends from 20Hz – 20kHz. So the phenomenon of binaural beats is allowing the brain to perceive a frequency that would not normally be possible.
Binaural beats differ to normal tones because they are the effect created by the brain when a different tone is heard by each ear. It is as if the brain has naturally mixed the two sounds to produce a new sound. Certain conditions need to apply for the brain to perceive this beats frequency. First, the frequency of the tones must be below about 1,000 hertz. Second, the difference between the two frequencies must be below about 30 Hz.

The history of binaural beats

Binaural beats were discovered in 1839 by Heinrich Wilhelm Dove, but it was not until 1973 that they attracted attention as a possible treatment method when Oster collected and published the results of modern research on binaural beats (also called auditory beats) in the brain (Oster, 1973). Oster claimed that binaural beats involve different neurological pathways than ordinary auditory processing. His research was followed up by Campbell (2007) and others who investigated the effects of binaural beats on consciousness. They attempted to reproduce the perceived effects of reported out-of-body experiences.
This research was a contributing factor in the formation of the Monroe Institute, a charitable binaural research and education organization. According to their website, the Monroe Institute “provides experiential education programs facilitating the personal exploration [and evolution] of human consciousness.” The Monroe Institute has developed a type of binaural beats which they call Hemi-Sync. It is used

… for integrating brain functions, … for mental, emotional, and physical healing through the use of varied binaural sounds

These are some of the strongest claims to be found on the Internet about binaural beats and the work of the Monroe Institute has clearly been a force behind the widespread popularization of binaural beats and the claims that are made for their usefulness.

Claims about binaural beats

As an example of one of the widespread claims about binaural beats on the Internet, one website says that:

Binaural beat audio tracks directly affect brainwaves and can positively alter feelings, behaviors, even your state of being.

We can divide this claim into two parts. First, there is the strong claim that “binaural beat audio tracks directly affect brainwaves.” Second, there is the hedged claim that “binaural beat audio tracks can positively alter feelings, behaviors, even your state of being.” At one level, both of these statements are hard to disagree with since pretty much any stimulus will affect your brainwaves, and any statement with can used as a modal operator is grammatically a statement of possibility and not a fact. Even if one person in a thousand is positively affected by binaural beat tracks, the statement can still be said to be true.
But the clear implication of this website’s claim and the claims on so many other sites on the Internet is that binaural beat audio tracks are good for you in some way. If we are to metamodel the quoted claim, some of the questions that we might ask include:

How specifically do they positively alter feelings and behaviours? (Modal operator of possibility)
Who says they positively alter feelings and behaviours? (Lost performative)
All binaural beat audio tracks? Which particular binaural beat tracks can have this effect? (Universal quantifier)
Positively in specifically which ways? For example, do they increase good feelings, or decrease bad feelings or …? (Simple deletion)

Below, I take up several of these questions to take a look at some of the research into binaural beats.

Why might binaural beats be effective?

In order to understand why bianural beats could be effective, we need to understand entrainment. Entrainment is the process whereby two interacting oscillating systems, which have different periods when they function independently, assume the same period. This was originally noticed by the physicist Christian Huygens in the 17th century by observing that two pendulums clocks started moving with the same period. The period of a wave is the length of time that it takes to complete one cycle. Since the frequency of a wave is the number of cycles per second, entrainment also implies that the frequency of the two oscillating systems also begins to match.
Sounds, music, and the human brain are all examples of oscillating systems, and it is possible for brain entrainment to occur in exactly the same way as the pendulums. In the example above, a perceived frequency of 10Hz corresponds to the alpha range of brain activity.
As noted above,the phenomenon of beats can allow the brain to perceive very low frequency tones that would not normally be possible. Being able to perceive a frequency of 10Hz is interesting because this is in the alpha range of brainwave activity. Table 1 below shows the well-accepted brainwaves with their related frequencies and the type of activity associated with each one.

Table 1. Brainwaves, frequencies, and typical activities
Brainwave type	Frequency	Typical activity
beta	15-40 Hz	aroused and actively engaged in mental activities
alpha	9-14 Hz	resting or taking a break
theta	5-8 Hz	daydreaming
delta	1.5 – 4 Hz	deep dreamless sleep

When the perceived beat frequency corresponds to one of these brainwave frequencies, the brainwaves entrain to the beat frequency and are postulated to generate the typical activity pattern.So the alpha range is associated with relaxation. The beta range will produce alertness. Entraining in the theta or delta range could produce deep daydreaming or sleep.

Particular Frequencies?

At least one website gives a very precise correlation between frequencies and a large number of medical/spiritual effects including alcoholism, opening of the third eye, muscle pain, confusion, depression, and arthritis. The list is described as including the following types of frequencies:

Brainwave frequencies associated with various mental states

“Healing” frequencies which could be used to heal illnesses of different kinds, or stimulate some region of the body (chakras).

Natural phenomena frequencies including natural frequencies that occur in nature (e.g. Schumann’s Resonance which is an aural pituitary stimulation to release growth hormone), as well as sound tones calculated from the revolution/orbit of the various planets.

Conclusion

This article has been a short introduction to the rationale behind binaural beats. While it does seem logically possible that brain entrainment may occur and positive effects may result from binaural beats, this article has not attempted to answer the questions raised in the metamodeling above though an investigation of research to determine whether these effects have been systematically corroborated.

References

Campbell, T. (2007). My Big Toe. Lightning Strike Books.
Oster, G. (1973). Auditory beats in the brain. Sci. Am. 229 (4): 94–102.