
Binaural beats - mdturnerphys
http://en.wikipedia.org/wiki/Binaural_beats
======
aroman
See also the coolest auditory illusion I know of:
[https://en.wikipedia.org/wiki/Shepard_tone](https://en.wikipedia.org/wiki/Shepard_tone)

~~~
eksith
I _knew_ that sounded familiar!

"In The Dark Knight and the follow up The Dark Knight Rises a Shepard tone was
used to create the sound of the 'Batpod' \- a motorcycle that the filmmakers
didn't want to change gear and tone abruptly but to constantly ascend."

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redact207
Many years ago I worked on a now defunct project (RapidLingual.com) that mixed
binaural beats over spoken language lessons. Binaural beats had been marketed
for a long time as a 'super learning' technique that could induce a state of
mind that's more focussed and receptive of a lesson (though the theory was
there, there was no study that confirmed it).

Unfortunately the guy who was supposed to write the lessons never really did
his part and the whole thing collapsed, but it gave me a chance to play around
with it and noticed:

\- Binaural beats are common in urban environments for things like air
conditioner units that resonate at slightly different frequency, but pair up
for a loud binaural pulse

\- Adding white-noise enhances the effect of the beats (you find similar
backing noise in products like Holosync)

\- You can only encode to FLAC. Because of the lossy psycho-acoustic nature of
Mp3 encoding, it strips out the inaudible part of waves that you apparently
need

\- For a trippy experience, I wrote a program that fades the screen (red-
black) in sync with the beats

~~~
humbledrone
> \- You can only encode to FLAC. Because of the lossy psycho-acoustic nature
> of Mp3 encoding, it strips out the inaudible part of waves that you
> apparently need

This is not correct. You can lossily compress the audio that produces binarual
beats and it's just fine. All it really is is two pitches being played, one of
the left channel and one on the right. The two channels play tones that are
almost the same pitch (but not quite, usually separated by 4-20 Hz). There's
no inaudible part of the waves. Two sine waves work great, with no harmonics,
and nothing inaudible about them. Unless your mp3 encoder is changing the
pitch of the sine waves (which it isn't), it will work perfectly.

You can find all sorts of (compressed) Youtube videos with binaural beats that
are reproduced correctly.

~~~
redact207
I said "apparently" as I never noticed a difference between flac and mp3.

What I read was along the lines of - one technique mp3 uses is to remove the
parts of a sound file that the human ear doesn't actually hear - parts which
would appear in flac and that apparently do have an effect of the beats.

Could have just been marketing hocus pocus, but who knows as all the encoded
beats online appear as mp3s.

~~~
melloclello
MP3 tends to remove some of the phase information (though I don't know how
applicable this would be at lower frequencies) from the signal, which would
quite likely have some effect on binaural beats.

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karlb
While we're on the subject of the brain handling things at a more raw level
than you might expect, here's another interesting group of experiments:
[http://en.m.wikipedia.org/wiki/Mental_rotation](http://en.m.wikipedia.org/wiki/Mental_rotation).
At university, we carried out some of Shepard and Merzlar's experiments to
measure the rate at which our minds could rotate objects. Even though it
subjectively feels like the mind has a graphics card that can rotate objects,
it was still surprising to discover that the perception isn't an illusion—and
to be able to measure our own mental rotation rates in degrees-per-second.
It's not mentioned on the Wikipedia page, but I remember carrying out an
experiment that showed that if it takes you, say, one second to mentally
rotate an object by 60 degrees, then at the 0.5-second mark, you really do
have a mental representation of an object that's rotated halfway (i.e., by 30
degrees). Maybe this isn't surprising to some people, but psychology is full
of examples of the brain taking outrageous shortcuts, so it surprised me that
mental rotation—which would appear to require a prohibitive amount of
processing power—isn't being fudged by the brain.

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milkmiruku
Here's some software for generating them;

[http://gnaural.sourceforge.net/](http://gnaural.sourceforge.net/)

[http://discord.sourceforge.net/](http://discord.sourceforge.net/)

[http://sbagen.sourceforge.net/](http://sbagen.sourceforge.net/)

[http://entrainer.sourceforge.net/](http://entrainer.sourceforge.net/)

~~~
eurleif
Or, since this is Hacker News, you can use ChucK, which is a realtime
programming language for processing audio:

    
    
        SinOsc left => dac.left;
        SinOsc right => dac.right;
        300 => left.freq;
        310 => right.freq;
        while (1) 1::second => now;

~~~
chinpokomon
The last time I looked at ChucK had to have been almost 5 years ago. I was
doing some interesting phase shift work where I would offset one channel by a
few samples. Lots of fun.

~~~
nitrogen
Are you talking about a fixed offset, as in
[https://en.wikipedia.org/wiki/Haas_effect](https://en.wikipedia.org/wiki/Haas_effect),
or a variable offset, sort of like a flanger?

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petercooper
Another entrant in the fascinating club of _" weird but cool sounding things
tried in our teens/20s in the hope they blow your mind but invariably don't"_
alongside lucid dreaming, smoking banana peels, and staring at the back of
someone's head to see if they can sense your voodoo powers.

~~~
swombat
Lucid dreaming is actually pretty cool and did blow my mind. It's essentially
not that different to temporarily being a god, with complete control over your
environment. Takes a bit of getting used to, to not wake up as soon as you
realise you're lucid dreaming ("oh my god, how exciting! Wait, no, don't wake
up now!"), but once you get that down, your imagination is the limit. Pretty
mind-blowing imho.

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mdturnerphys
Make sure to try the demo at the top of the page. Our auditory system is
really neat.

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blissofbeing
I have been running
[http://healingbeats.com/forum](http://healingbeats.com/forum) a large forum
related to Binaural Beats for awhile, some good sbagen presets there.

Here is a good place to create and listen to binaural beats on your browser
using the new html5 audio apis:

[http://mindstate.michielroos.com/binaural-
beats/](http://mindstate.michielroos.com/binaural-beats/)

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mugsydean
90 percent of them dont seem to have much effect, but i found a few that
seemed to put me in a super deep sleep... like an audio mind massage. pretty
sure it was a 3hz delta state, with out any weird static noises mixed in. i
find those static sounds somewhat annoying, but did find a pleasant one with
nature sounds mixed in there.

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14113
You get theese when the instruments in a section of an orchestra or band are
out of tune. It's a very good "lazy" way of checking to see who's out of tune
if you don't have perfect pitch.

~~~
mdturnerphys
As pointed out elsewhere in the comments, this is different.

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impendia
This can be easily heard on a piano. Just play two adjacent low notes at the
same time and volume.

~~~
mdturnerphys
No, it's different. That's a real beating effect. This is an phenomenon that
happens when the two tones are heard separately in each ear and the beating
just happens in your head. It tells us that our auditory system retains some
waveform data, up to about 1000 Hz.

~~~
bigiain
This is what I find fascinating about it.

I understand from a math/physics perspective why a microphone places betwen
two sound sources playing slightly different frequencies "hears" the beat
pattern. I _don 't_ understand why that still works once the two individual
signals have made their way into your audio nerves and brain. (If I didn't
have actual _work_ I shoukd be doing now, I suspect I'd happily drop into a 6
or 8 hour wikipedia and google mediated deep-dive laymans research session.)

~~~
iyulaev
It's a phenomenon that happens to all waves, whether they are acoustic or
electromagnetic. In fact, it's how your clock radio tunes to various stations.
This property is a mathematical property of all waves, hence even when your
brain mixes an electrical representation of the sound going into your left and
right ears, you still get the effect.

~~~
mdturnerphys
For higher frequencies your auditory system doesn't retain the waveform
information, so this doesn't happen.

~~~
bigiain
I wonder if that's an evolutionary thing – somehow we evolved out the ability
to retain phase difference information outside the frequencies where it's
useful for stereo angular location?

The "~1000Hz" upper limit is pretty close to a 1/4 wavelength for a "phased
array" of two ears ~100mm apart. That'd make it pretty ideal for angular
discrimination based on phase difference.

~~~
apl
You're pretty spot on here -- up to approximately 1500Hz, the auditory brain
can make use of so-called inter-aural time differences which allow estimation
of a given source's azimuth. After that, phase differences become ambiguous
and the brain relies more heavily on inter-aural volume differences.

[http://en.wikipedia.org/wiki/Interaural_time_difference](http://en.wikipedia.org/wiki/Interaural_time_difference)

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3838
it's the pulsing that induces the altered states, you can use a metronome-like
sound for similar results, this ones at 9hz which is mid alpha - absorbed in a
good book frequency

a quick bit of supercollider code: play{SinOsc.ar(369.99,0,LFPar.kr(9))}

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cLeEOGPw
Knew about them for a long time. I am still not sure if these work for some
people or not, because they don't work for me at all.

~~~
a_bonobo
I don't think they work at all, especially because there are no studies
proving binaural beats to be good for anything (except making money?). The
only blind study Wikipedia cites was published in the "Journal of Alternative
and Complementary Medicine", which isn't really a journal at all.

Edit: Found this study [1] looking at binaural beats and changes in EEG:
"Analysis of changes in broad-band and narrow-band amplitudes, and frequency
showed no effect of binaural beat frequency eliciting a frequency following
effect in the EEG". This study is (conveniently) not cited in the Wikipedia-
article.

[1]
[https://www.sciencedirect.com/science/article/pii/S016787601...](https://www.sciencedirect.com/science/article/pii/S0167876012006241?np=y)

~~~
joedevon
I'm convinced they "work" when done correctly. If the current brainwave
frequency is too far from the desired state, the entrainment may not work,
from what I've read. I hope they do more studies.

I first found out about binaural beats and brainwave entrainment in the 80's
reading a book called MegaBrain by Michael Hutchison.

I went to his seminar. There was a device that generated binaural beats via
audio and some flashing lights.

I closed my eyes, put on the headphone/helmet thingie. Did the program. My
mind was 100% on the ball. Pshaaaw. Felt like nothing happened. Was skeptical.
Gave up on it. Took off the helmet. Stood up. And fell back into the chair.
Because the brainwave entrainment put me into a sleepy state.

While I understand that placebo's are powerful, I find it hard to believe that
I imagined that deep a sleep, particularly when I had decided that it didn't
work.

Flash forward years later, I figured they must have an app for the iPhone by
now. So I searched and found several, but settled on an app called Brain Wave,
by Banzai Labs. It isn't quite as strong an effect as with the light machine
combined, but it does seem to get me into a deep sleep.

I understand this is anecdotal. Try downloading an app, do a program and judge
for yourself.

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Dewie
I have used brainwave entrainment before, to aid myself in meditation and to
help me visualize. It did help me feel that I got into more of a
meditative/trance state while using them, but sometimes it worked too well and
I fell asleep (it doesn't help that I meditate lying down in my bed).

When I actively used stuff like that (many years ago), I had the impression
that bineural beats in particular weren't useful. However I tried to Google it
and I wasn't able to easily confirm my memory, so I guess it's up in the air
for me.

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mugsydean
The UAE has banned some of the aps. Thats what finally got me to try them out.

