Cool Edit's Brainwave Synchronizer

DSP, Plugin and Host development discussion.


Any insight on how Cool Edit's Brainwave Synchronizer might have worked? My next project could be reviving that old effect into a VST plugin, for convenience (and since i'm on an ARM mac and can't run XP vms).
My guess is that each channel was processed with a bode shifter with different frequency shifts each, however with this approach I'm still quite far from how it sounded originally. I can't really find any documentation online on how it works, besides basic user manuals.
PS: I'm not really interested in the brain/health effects of it (doubt there are any), it just sounded very cool.


Sounds like binaural beats. From memory, the wavering between two pitches is supposed to make your brainwaves match the frequency difference. Example: play a 40hz tone in the left ear, and a 42hz tone in the right and there you go, your noggin is ticking on the 2hz vibes. Not sure how Cool Edit's contraption works but I'd guess it's similar to how I've described. Isochronic tones are similar but work by using a short pulse to alter your brainwave frequency.


Yes, but what's interesting is that Cool Edit applied some processing to an already existing audio file, it didn't generate tones (it could but through another utility). Manual says each sinusoid "modulates" the original audio file but i'm not really sure how. My guess for frequency shift came from the percieved final sound and some mentions of effects similar to barberpole phasers in forums/documentation.

For example, if I want a beat of 4Hz i can shift the left channel up 2hz and the right channel down 2 hz.

Just a hypothesis though.


There's a frequency shift but it would be a small fixed amount as you've described. I think a phaser type effect would introduce too much modulation although the end result may be somewhat reminiscent of a phaser effect.

I'd suggest reading the manual if you can get your hands on it.


gambero wrote: Mon Jan 08, 2024 3:51 am For example, if I want a beat of 4Hz i can shift the left channel up 2hz and the right channel down 2 hz.
That's the usual way to do it.. though keep in mind that because Bode-shifters rely on filters to get an analytical signal (and to deal with aliasing, though that's not a huge deal with small shifts like these), it might still sound a bit different if the filters are different. The low frequencies in particular are tricky if you want to use linear-phase filters. No idea what CoolEdit does in particular, but you might be able to get some clues if you feed it a test signal and see what the results look like on analyzer (ideally with large enough beat frequency that the peaks are visible separately).


How is a bode shifter built? Is it a series of allpass filters where cutoff is modulated with an lfo?


Tried to explain but my terminology is still trash :lol:
Here the source code explains it quite well ... r_1431.xml

(line 103 is where the magic's at)


Basically you need to generate a complex analytical signal from the real one. You can either get that by filtering the real signal with an approximated Hilbert transform (e.g. windowed FIR of the ideal one) or a pair of allpass filters that are designed to have a phase shift of 90° between each other. Note that the latter will alter the real part as well, so it's not perfectly reconstructing.

Then you simply multiply the complex analytical with a complex sinusoid of the shift frequency and take the real part of the result.

The allpass pair is what you'll typically find in FX, the Hilbert transform less so as it's more expensive and has half a window size latency.


fwiw: this is what the cool edit pro v2 manual says. I was going to take and post photos of my manual, but found this one on line. pages 178-179.

The options in this menu can be used to introduce some processing effects that are both innovative and wild-n-wacky. Have fun and experiment!

Brainwave Synchronizer…
Cool Edit Pro’s Brainwave Synchronizer can produce files that, when listened to with stereo headphones, will put the listener into any desired state of awareness. For example, by listening to “brainwaved” files, you can achieve states such as deep sleep, theta meditation, or alpha relaxation. Because of the nature of this function, it only
works on stereo waveform data, and to be effective, it must be listened to with stereo headphones.

The Brainwave Synchronizer function spatially locates the audio left and right, in a circular pattern over time. In order to spatially encode the signal, either the left or right channel is delayed so that the sounds will appear at each ear at different times, tricking the brain into thinking they are coming from either side. When this is done at frequencies of 3Hz and above, the brain will start synchronizing at the same frequency, increasing its output ofDelta, Theta, Alpha, or Beta frequencies.


Frequency Graph
Time is represented along the x-axis (horizontal edge), and frequency along the y-axis (vertical edge). As you go to the right of the graph, you are setting the frequency characteristics of the highlighted sample later and later intime. The settings chosen will vary between the low and high settings depending on where the graph dictates the
signals should be. Choose the highest and lowest frequencies that are represented on the graph with the scroll bars located in Low/High Settings, below. The readout below the graph displays the current x, y position of your mouse.

Cycling between 4 to 5 Hz over a 2 minute span works nicely. If large variations are done in short time spans, the effects are not as pronounced. For example, after 5 minutes of listening to Theta waves, the listener will become slightly awake, if 30 seconds of alpha waves are generated, and then returned back to theta. The effect is sort of like shifting gears into different levels of awareness.

For more information about Cool Edit Pro’s graph controls (such as how to add and remove control points), see the
“Getting to Know Cool Edit Pro and Its Main Screens” chapter.

Smooth Wave
When checked, the audio that appears at the left and right channels will be smoothed out. The left and right chan-nels will delay and un-delay following a smooth curve such that the delay difference between the left and right channels will follow a sine wave pattern, even though the brain will hear the audio as traveling around the head in
a circle.

When Smooth Wave isn’t checked, the net delays are the same, but are achieved by holding one channel constant (at no delay) while the other channel is delayed following half a sine wave. The boundary between holding non-delayed and delaying signal is discontinuous in that the dD/dt (difference in delay over time) jumps from zero to a positive delay value without hitting any values in-between. When Smooth Wave is checked, the dD/dt is alwayscontinuous, which will cause less noticeable distortion in either channel when heard independently.

Spline Curves
Check this option to generate a smoother, best fit curve instead of a straight line between control points on the graph. When you use spline curves, the line will not ordinarily travel directly through the control points; rather, the points control the shape of this curve.

To get the curve closer to a control point, click to create more control points near the point in question. The more control points there are clustered together, the closer the spline curve will be to those points. Use Spline Curves when you want very smooth curves instead of straight lines (with their discontinuities at the control points).

Pressing the Flat button will reset the graph to its default state, removing all control points.

Low/High Settings
There are two sets of settings for control of brainwave frequencies. Low Settings all correspond to the lower part of the graph (points dragged near the bottom), and High Settings affect the top.

This is the brainwave frequency that will be encoded into the final process. Different brainwave fre-quencies stimulate the brain into synching to different levels of consciousness (e.g. sleep, meditation, awakeness, etc.) . For special spatial panning effects, choose wave frequencies of 1Hz or less. A mono source (left and rightthe same) will appear to move from left to right and back at period of 1/frequency. For example, a fre-quency of 0.1Hz will pan the audio in a "full circle" over the period of 10 seconds.

This controls the intensity of the brainwave encoding. Higher intensities work well with lower brainwave frequencies. Beta waves should have intensities below 25 or so, while Delta waves work better with inten-sities above 60.

You may choose to have your brain think the synchronization frequencies are coming from the left or right. This may affect the left or right hemispheres more intensely, but that’s only a guess. Mixing a file that has been brainwaved to the left with one that has been brainwaved to the right (in the same fre-quency range within 2 Hz) has interesting effects.
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I'm not a musician, but I've designed sounds that others use to make music.


Shabdahbriah wrote: Tue Jan 09, 2024 2:59 am fwiw: this is what the cool edit pro v2 manual says. I was going to take and post photos of my manual, but found this one on line. pages 178-179.
Thank you!

Well this is interesting, here it is described as haas (probably?) auto panner. Didn't really sound like that to me, but I might be wrong.
I'll have to find an old thinkpad or something to measure it for real, my Windows PC is dead (hence the vst plugin project). If anyone's interested I'll keep you updated on my findings.


Update! (Sorry for reviving)
I saw that this effect is still present in Adobe Audition under the name "Binaural Autopanner", so I will stop any research on it.

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