Comment by redact207 | Hacker News Reader

Comment by redact207 | Hacker News Reader

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

> - 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.

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.

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.

It depends on whether you're using pure tones, or phase shifted audio. Binaural beats in phase shifted audio do not survive MP3 encoding, and require a high quality setting to survive Vorbis.

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