Hi AdamTheMechE,

I’m glad you like the project.

There are ways of making an audio player become a Brain Machine. But it’s a little trickier than you suggest. This is because the audio and the blinking LEDs work differently.

The two LEDs blink directly at brainwave frequencies (in the case of this simple Brain Machine, they blink at one of four frequencies, one for Beta, one for Alpha, one for Theta). For instance, for Beta, the LEDs on each eye blink at 14.4Hz

The two speakers, however, create the brainwave frequencies via binaural beats, which means that the brainwave frequency is the result of the difference between the slightly different frequencies in each ear. For instance, to create Beta waves, one ear gets 415.0Hz, and the other ear gets 400.6Hz, the difference being 14.4Hz, which is the low end of Beta.

Using audio editing software, it is very easy to create an mp3 file that generates a 400.6Hz sinewave on one channel, and then goes through a sequence of offset frequencies in the other ear — this could create the exact same sequence as the Brain Machine.

Making an mp3 player do the blinking LEDS is not as easy. There are two reasons: 1) we need a third audio channel for the LED information; 2) mp3 players only play in the audio range, and brainwave frequencies are below this range — so we would need a way to convert higher frequencies into lower ones. There are ways to do this — such as a divide-by-256 counter, and then use a square-wave at 256 times the desired frequency. And, probably the easiest way to create the third channel is to use two mp3 players, and just start them at the same time (It is probably better, but it probably isn’t way important that the LED blinking and the audio be exactly in synch.)

If you play with this, or other ideas like this, please post to the blog again and give your results.

Cheers,
Mitch.
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