PC Based using Sound card

Wow, I did ALOT of searching on the 'net and it seems that I am the first person to ever try this. It took me a good few days research to find out all the facts on this page so I hope you appreciate it. Also, I have very little electronics knowledge, and I haven't accurately measured any of the signals produced with this method (it will also vary according to your sound card, volume, software, etc.) so while I haven't noticed any negative effects yet this may well be fatal. If you stop hearing updates from me I suggest you discontinue use immediately :)

The situation

You may already have everything you need to build a relatively advanced CES device right now. The theory here is that you computer is alot more advanced that the microprocessor found in most CES units -- using the right software you can generate very complex and fun waves to be sent straight into your brain :) And, standard earclips can plug straight into your regular 3.5mm line-out jack of your PC (and if you don't have earclips you can make them quite easily).

WARNING: This may well cause fatal brain damage... I seem to be the only person in the world publicly researching this so until we more info, USE THIS INFORMATION AT YOUR OWN RISK AND/OR PERIL.

IMPORTANT STUFF WE NEED TO FIND OUT: The voltage and ampere output of the average sound card. [SC->] Line level (signal level) output is 1 volt RMS. Cheaper sound cards will do a little less, more expensive ones can do more. The speaker jack output could in theory get up to several volts (depending on the design). Amperes (amps) is the bigger concern here. Amps are what can give headaches and kill. Most medical papers I've read so far tend to use 1mA (milli-amp, 1/1000 of an ampere) or less (with a warning to not go over 10mA). The average line level out jack can do anywhere from 5-30mA. The average speaker level output will be quite a bit above this. Sound card volume control will vary BOTH the output voltage and amperes out. It's likely that the desired ratio will not be ideal, so usually a simple current limiting resistor should be added to drop the amperes. Warning: More is not necessarily better here. Brain waves are signal levels, not cooking levels. My preferred setting is 1-3volts peak with 1-3mA. A general rule of thumb: if it hurts, it is too much. A person should be able to be jacked on for at least an hour using a constant wave form without experiencing pain. Each person will be slightly different, so there is no one universal setting that is good for everyone.

Frequencies

CES units use bi-polar square waves (the current alternates in each direction at particular intervals -- this prevents ionization amongst other things). Audio circuitry is not very useful for generating sign waves. You can check this by generating a square wave with your favourite Audio editor (try Adobe Audition for the PC or the freeware Audacity for Linux), and playing it back while recording and you will see it looks very different. It reaches a +1 or -1 amplitude but only for a very short time and it can't sustain it. However, from about 10 Hz (I think this is what most sound cards are rated at anyways) the results seem to be acceptable. (This is the case on my sound card... additional test results would be appreciated).

This means however that the cool dopey effect seen from the Voodoo Magick Box at 0.5 can't be reproduced. Away around that with some electronic knowledge is to build a circuit to Convert sine waves to square waves - then you can generate regular sign waves with your PC which your sound card can reproduce and this circuit will convert them to the required square waves. I haven't tried this!

Of course, we may also want some other nice frequencies below 10 Hz for brainwave entrainment and other things. A way around this might be modulation. So we have a carrier frequency of say 100 Hz (which is the other popular frequency amongst CES units) and modulate it with our desired frequency. I haven't tried this yet either, I will do more research on it, but anyone who has their own EEG your help would be greatly appreciated!!!

Note: the higher frequencies are alot more pleasant than the 0.5 Hz frequency. It's like a pleasant massaging buzzing on your ears :) You can adjust the intensity with the software mixer of your PC -- you'll probably need to max out the Master control and the regular Wave/PCM control.

Cool stuff

Higher frequencies such as 100 Hz are audible by the human ear. Wanna see something freaky? If you have external amplified speakers, hold their connector while you're jacked up... or just touch it anywhere to your body. You'll hear the same sound you would have heard if they were plugged directly into the PC, just a little bit softer. If you're using frequency modulation, you can hear this very clearly... it's pretty cool. Does anyone know if this is dangerous? :)

Software

Adobe Audition is really nice because in the Generate->Tone dialog, there is a preview mode to hear the wave without generating a few seconds in advance. In this mode you can adjust all the settings responsible for the wave's final form and you can feel the effects straight away. Incidentally Adobe Edition is based on the original Cool Edit program, which has built in features for binaural brainwave entrainment.

Call for information

There is no other information about this subject on the 'net. PLEASE -- if you have decent electronics knowledge and equipment and can assist with any info or self experimentation :), PLEASE CONTRIBUTE INFORMATION to this page.

External Links

• Sound card based signal generators
• Pocket PC signal generator (commercial)
• USB-based signal generators (commercial +/- $800)