What kind of effect does 'binaural beat', which is said to have a healing effect, have on actual brain waves?
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Binaural beats , which use the 'swell' of the sound generated by letting the left and right ears hear sounds with slightly different frequencies, are said to have a healing effect by the low frequency signal generated by the swell acting on the brain waves. .. You may have heard of the sound sources that actually sang the effects, but the results of verifying the effects of such binaural beat sound sources at the brain wave level have been announced.
Do Binaural Beats Really Affect Brainwaves? — The Autodidacts
http://www.autodidacts.io/binaural-beat-openbci-eeg-experiment/
◆ What is 'binaural beat'?
Binaural beats means 'binaural beats' in Japanese. For example, if you hear sounds with slightly different heights, such as '440Hz' for the right ear and '445Hz' for the left ear, the sounds are synthesized in the brain to produce a difference of '5Hz', which is a meditative state. It is said to induce the 'θ (theta) wave' seen in, and is said to have a relaxing effect and a healing effect. For the actual binaural beat sound source, you can listen to a sample at the following site, and you can also find various sound sources on YouTube and so on.
Effects of Binaural Beats | Binaural Beats Japan
Binaural beats are based on this theory, but it is also true that there are voices who question their effects. The Autodidacts , a site that means 'self-taught,' conducted experiments aimed at elucidating the pros and cons of binaural beats at the brainwave level, and published the results on a blog.
◆ Measure brain waves
The Autodidacts research team decided to use Emotive's Emotive brainwave sensor headset, Epoc, to measure changes in brainwaves that occur in different parts of the brain. Epoc is a headband type EEG (brain wave) sensor equipped with multiple brain wave sensors, and it is a product that anyone can purchase because it is commercially available to the general public.
First of all, the research team proceeded with the experiment using Epoc, but unfortunately the data obtained with Epoc is limited, and it turns out that the data recording ability and analysis that were really needed cannot be performed. Therefore, this time, when detailed verification was carried out using OpenBCI , an open source brain wave scanner system, it was said that it succeeded in recording the targeted data.
In the experiment, as shown in the figure below, multiple electrodes were attached to the head, and changes in the brain waves of each part caused by playing the binaural beat sound source with headphones were measured.
The subjects headphone 'for Sony business
The procedure of the experiment is as follows, and the total time required is about 20 minutes.
・ 30 seconds of silence
・ Control group 1: Pink noise (5 minutes)
・ Experimental group 1: 17Hz binaural beat sound source (5 minutes)
・ Control group 2: Pink noise (5 minutes)
・ Experimental group 2: 17Hz binaural beat sound source (5 minutes)
The measured EEG data was saved as CSV format data and analyzed using Python's NumPy and matplotlib.
Here is the spectrogram of the frequency characteristics of the brain waves measured in this way. The vertical axis is the height of the frequency, and the horizontal axis is the graph showing the flow of time in seconds. It turned out that the effect did not appear so much.
In the figure above, we saw the flow of time, but in the following we will look at the frequency distribution. The horizontal axis shows the frequency distribution of brain waves, and the vertical axis shows the intensity of each frequency. It can be said that it is a cross-sectional view of the spectrogram above. The gray graph shows the brain waves when listening to pink noise, and the orange graph shows the brain waves when listening to the binaural beat sound source, but again there is a clear difference between the two. It is clear that it is not.
These graphs are plots of '8 channel' data out of multiple measured brain waves. The experimental team also graphed the data for other channels in the same way, but the results show that there was no clear difference as well.
◆ Conclusion
Based on the experimental results, the research team concludes that 'binaural beat sound sources do not have a clear entrainment on brain waves.' In the experiment, in addition to 17Hz, 8Hz binaural beat sound source was also tested, but it was said that no clear result was confirmed here either.
The experimental result was that the effectiveness of the binaural beat sound source at the brain wave level was denied, but the research team said that 'there are some restrictions on the experimental content', and further verification is required for the following points. Also touches on.
・ Verification time
This time, we decided that an experiment divided into 5 minutes was appropriate, but in reality, an experiment that took a longer time may be required.
·frequency
This time, I used binaural beat sound sources of 17Hz and 8hz, but there is a possibility that different results were obtained at other frequencies. The effects of binaural beats may only appear at specific frequencies.
・ How to choose a subject
Two subjects participated in this experiment, but it is probable that there are individual differences in the effects of binaural beats. The presence or absence of effectiveness should be verified using more subjects.
In publishing the results of this experiment, The Autodidacts prefaced that 'we are not EEG experts,' and cautioned that there may be some mistakes in the verification methods and data. Since the brain wave data (CSV file) and analysis data obtained in the experiment are open to the public, it may be interesting for those who are interested to refer to it.
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