I enjoy the show Fringe but I often feel disappointed in myself that while I usually have a number of contraptions in various states of progress on my work bench, none of them are worthy of Walter Bishop’s attention. I happened to be researching building an ECG to monitor brain waves for a different unrelated project and got diverted into reading up on brain wave entrainment and using binaural beats. Now I was already aware of this phenomenon before but it never really peaked my curiosity until I realized that this was an opportunity to do something a little Fringe-like… seeings as my wife still won’t let me put an isolation chamber in the garage.
Binaural beats are a perception phenomenon where if you listen to a tone in either ear that are a small frequency difference apart your brain processes the sound unusually. Instead of hearing two distinct tones you hear the interference pattern as a set of beats that appear to emanate from the center of your head. As if this weren’t cool enough, the range of frequency differences necessary to create this perception happen to be in the range in which brain waves operate. This can be exploited in what is called brain wave entrainment wherein if for example you were to have a 30hz resting brain wave frequency and were subjected to a binaural beat of 25hz, your brain would idle down to match the 25hz… your brain wave is entrained.
Here is a sample of a 10hz Binaural Beat
As the brain wave is slowed the subject in theory should be subjected to certain mental states usually reserved for meditation, dreaming and comas.
| Frequency range | Name | Usually associated with: |
|---|---|---|
| > 40 Hz | Gamma waves | Higher mental activity, including perception, problem solving, fear, and consciousness |
| 13–39 Hz | Beta waves | Active, busy or anxious thinking and active concentration, arousal, cognition, and or paranoia |
| 7–13 Hz | Alpha waves | Relaxation (while awake), pre-sleep and pre-wake drowsiness, REM sleep, Dreams |
| 4–7 Hz | Theta waves | deep meditation/relaxation, NREM sleep |
| < 4 Hz | Delta waves | Deep dreamless sleep, loss of body awareness |
So I sought to explore this by setting about to encode binaural beats into ambient music. At first I came up empty on commercial tools to support the audio effect I needed. Remember, this is NOT pitch shifting, this is frequency shifting… the two are very different in that pitch shifting maintains harmonic ratios whereas frequency shifting is a linear translation. Given a wave pattern consisting of a 500hz and 1000hz tone, pitch shifting would allow you to shift (x2) this to 1000hz and 2000hz, whereas frequency shifting would allow you to shift (500hz) this to 1000hz and 1500hz. Pitch shifting retains the musical qualities, think of it as playing up an octave, while frequency shifting destroys any harmonic ratios. While there are a lot of pitch shifters I was initially forced to work on writing my own fast fourrier transformation to perform frequency shifting. Somewhere along the line though before finishing I did find a free commercial VST plugin that did this already! So I scrapped my code and put this plugin to work (which was a pain because it was based on a java VST base).
With just a couple clicks I was then able to take a playlist, mix it mono to both channels, and shift the left channel up X freq and the right channel down X freq to produce a binaural beat of 2X freq.
After producing some test tracks I was pleased to find that the audio distortion was only very subtle and the mental affects ranged based on test subjects.
I improved on this approach by using Sony Vegas with this VST and taking advantage of envelopes to not only apply a Frequency Shift, but to actually taper the shift over the course of the track. Said another way, the track starts with a beat of perhaps 35hz and gradually slows until it reach 4hz at the end. This was based on some research I came across that purported to find that entrainment was far more effective when the difference between the current brain wave frequency and binaural beat was small. By tapering slowly it ensures that I will not only “catch” the listener at their resting rate but be able to effectively drive them into Delta wave territory.
I have successfully produced some tracks of this sort, here is a link to one based of Buddhist monks chanting with a binaural beat starting at 25hz and ending 1 hour later at 4hz. Because this requires tight stereo listening, you will need head phones to get the full affect. The vibration you hear isn’t there… listen to just one side of your headphones and you wont hear it, your brain is inventing that.
After this experiment I then wanted to build what I was calling a binaural beat-box (hehe). It is a box with two eighth-inch plugs and a dial that goes from Coma to Cocaine. You can plug in things like an IPod on one end and headphones on the other. The software processes I described above would essentially take place electronically. I spent a lot of time researching how to accomplish this electronically and it is awfully complicated. Fortunately the process is very similar to long range radio transmission process developed during the 1920s called Single Side Band Modulation. It is still used by Ham radio operators today. It is a little too complicated to explain how it works but effectively it allows you via modulation over quadrature oscillators and filtering to shift the frequency in realtime. Before digging in too far though I then looked into creating this in realtime in an Android app and while clunky was able to eventually do this although the source code is long lost at this point though. I also created a relatively robust .NET desktop tool as well.
