The beat is low and steady – but it’s all just in my head… While I’m sitting on my couch, listening to some smooth jazz, there is a faint beat in the background. It doesn’t seem remarkable – except for the fact that I can’t hear the beat from my headphones. Instead, I sense it in the center of my brain.
Binaural beats are like optical illusions for sounds. When your left ear hears a slightly different tone from your right ear, you perceive a beat not present in the music you listen to. These binaural beats (from Latin “with both ears”) have been peddled as “digital drugs”, producing all sorts of effects from improving sleep to enhancing your memory.
For example, recently the pharmaceutical company Bayer, manufacturer of Aspirin, put seven files of binaural beats on its Austrian website. The idea: by making you relax, the beats may put you in a relaxed state, which could alleviate headaches. But it is far from certain whether this idea – and many others about binaural beats – hold true.
The binaural beat percept
Let’s take a loudspeaker. We’ll play two sine waves, one with a frequency of 440 Hertz (cycles per seconds) and one of 446 Hertz. The sound travels to your ear and the two waves interact with each other, either cancelling each other out or amplifying each other. The sound waxes and wanes periodically: this is called a beat, specifically a monaural beat.
The frequency of the beat is equal to the differences in frequency between the two original sine waves – in this case, 6 Hertz.
Now, let’s take a set of headphones. We’ll split the two waves, and play a sine wave of 440 Hertz in your left ear and a sine wave of 446 Hertz in your right ear. Now, what do you hear?
Again, you’ll hear a beat of 6 Hertz. But now there is no room for the two waves to physically interact – it is all in your head. While monaural beats can be heard when you listen with both ears, one ear is enough to perceive them (hence “monaural” from the Latin phrase “with one ear”). Binaural beats, however, can only be perceived with both ears, hence their name derives from “with both ears”. They also differ in how you perceive them: monaural beats pulse from very loud to silent, while binaural beats only change slightly in volume.
We still do not know for sure which brain regions are involved in generating the binaural beat percept. A part of the brain called the superior olivary nucleus may be one such region, but this is not yet certain.
- Sample clip of a binaural beat Binaural-Beat-Clip 1.mp3 (Disclaimer: Please consult your doctor before listening to binaural beats if you suffer from any neurological disease or have had a stroke.)
Heinrich Wilhelm Dove, a German experimenter, first discovered binaural beats in 1839. Much of what we know about binaural beats comes from an article by Gerald Oster, published in Scientific American in 1973. Oster envisioned binaural beats as a tool in research and medicine, allowing researchers to investigate the neuronal basis of hearing.
He might be surprised if he did a quick Google search to see what binaural beats are used for today. A whole industry has been built on the illusion (as we’ll see) that binaural beats improve your wellbeing. These claims range from helping you meditate, increasing your IQ, making you relax and sleep, promoting creativity, reducing anxiety, to activating your self-healing abilities.
In September, the pharmaceutical company Bayer released seven tracks of binaural beats on its Austrian website. Presented under the title “Good Vibes for our brain – powered by Aspirin”, the website proposes that binaural beats are “a pleasant and easy way to e.g. alleviate headaches through relaxation”.
“But do binaural beats really affect brain waves?”
Bayer presents the tracks very cautiously (my emphasis): the “low-frequency sound may influence brain waves. […] Frequencies between 8-14 Hertz are called alpha waves, and occur mostly during a relaxed state. […] The resulting difference [frequency of our beat] is 10 Hertz. Thereby, alpha waves should be generated, which help to bring the listener into a relaxed state. A pleasant and easy way to e.g. alleviate headaches through relaxation.”
So note that Bayer Austria does not actually claim that binaural beats help headaches, merely that they may help you relax. But let’s breakdown the different parts of their statement.
Brain waves and binaural beats
Firstly, the brain waves. Brain waves are the neural oscillations seen on an EEG recording. In short, the EEG reflects the activity of many neurons, and is recorded noninvasively from the scalp. Sometimes, whole groups of neurons are active at the same time, and this can be seen as brain waves on the EEG. Different frequencies are associated with different tasks or mental states.
Gamma waves, which oscillate at 30-100 cycles per second, are associated with memory and attention. Alpha waves, at 8-12 cycles per second (or Hertz), are associated with an idle, restful state. When your eyes are shut and you are resting, your EEG would likely show up as alpha waves. Most websites trying to sell you “exclusive binaural beats” will tell you that their beats influence your brain waves, shifting them to a desired frequency and thus inducing that state, e.g., relaxation or memory. But do binaural beats really affect brain waves?
“Men and women may perceive binaural beats differently, and perception may change throughout the menstrual cycle.”
One way in which binaural beats may influence brain waves is through entrainment. Entrainment here means that the activity of your EEG becomes similar to a certain frequency set by an external stimulus. An example of entrainment is repetitive clicks: if you hear clicks at a certain frequency, your EEG is likely to show waves at this same frequency.
Another way binaural beats may influence your brain waves is through phase synchronization. It has been suggested, but not thoroughly tested, that auditory beats increase the synchronization of the phase of brain waves in different brain regions.
One study tested the effect of binaural beats on EEG rhythms in epilepsy patients. In some hard-to-treat cases of epilepsy, patients are implanted with electrodes to pinpoint exactly where in their brain a seizure starts (to stop seizures, this area can then be removed). In this study, 10 epilepsy patients were implanted with intracranial electrodes, and the researchers recorded their EEG response to both monaural and binaural beats to see how the beats influence brain waves.
The researchers found that beats can modulate oscillations and phase synchronization. But for binaural beats, they mostly observed a decrease in EEG power and phase synchronization. This means that there are weaker brain waves at the frequency of the beat, and the EEG phases across the brain fall more out of sync. Only when the patients listened to 10 Hz and 40 Hz binaural beats did EEG power increase, i.e., there were stronger brain waves at these frequencies. This entrainment had previously been described for 40 Hz binaural beats .
But will binaural beats make your headache go away? You can test it on yourself when your head hurts next time – but science says: we just don’t know, yet.
Binaural beats are not digital drugs
Now, could this entrainment really have an effect on your memory, creativity or pain perception? It is probably safest to say that the jury is still out on this question. A 2015 review of the available literature summarized several studies on the effect of binaural beats on memory, creativity, attention, anxiety, mood and vigilance. The authors concluded that for most of these applications, findings are either contradictory or only supported by a single study. The only consistent finding was that several studies reported that binaural beat stimulation reduces anxiety levels. How anxiety is reduced, however, is not yet understood.
One study suggested that binaural beats may increase relaxation after exercise. However, the subjects in this study listened to binaural beats in the theta range, 4-7 Hertz . Another study reported that study participants subjectively rated pain lower after they listened to binaural beats at 8, 10 and 12 Hertz, i.e., in the alpha range. So while there is no definite proof that binaural beats increase relaxation or reduce pain, further research may back this idea up.
And this is the problem with binaural beat research – we still do not know how the illusion of binaural beats is generated in our brains, or which brain networks are affected by them. If we knew, experimental standards could be harmonized and optimized to probe and report the effects of binaural beats more accurately. As it is, protocols vary widely between different studies – from which wave ranges are tested to how long subjects listen to beats and what background frequencies are used. All of these may impact the effect of binaural beats on brain waves, mood or pain – but we don’t know it.
Just a few examples of how funny these beats are: older people can detect beats in the gamma range, but not as accurately as younger people. Men and women may perceive binaural beats differently, and perception may change throughout the menstrual cycle. Given that we can’t explain these observations, we need to properly understand binaural beats before we can probe their effect. And yes, music might help you relax, and this might improve your headache – or mood, anxiety, creativity, or sleep. But will binaural beats make your headache go away? You can test it on yourself when your head hurts next – but science says: we just don’t know, yet.
Binaural beats on the website of Bayer Austria: https://www.aspirin.at/good-vibes/wie-funktionieren-binaurale-beats/
Oster: Auditory beats in the brain. In: Scientific American. 1973 Oct; 229(4):94-102
Chaieb et al. Auditory Beat Stimulation and its Effects on Cognition and Mood States. Front Psychiatry. 2015; 6: 70.