some electronic projects

building stuff, more stuff, and a little bit of… stuff

Make a “Flanagan Neurophone”-Like Device with a TL494

UPDATE: Try it with NO audio input and the frequency set to 40kHz! That may be all you need to amp up your IQ. More here: https://neurophone.wordpress.com/2014/04/02/a-new-way-to-neurophone/

Also, if you can’t afford the $800 Neurophone NF3, there’s a $99 Neurophone in the works… but it will only ever see the light of day if enough people express their interest! More details here: http://www.newneurophone.com/

UPDATE: Some people who have built this recommend using an 0.005uF capacitor for C2. Also, the piezos may be backwards. You may get better results wiring them so that the crystal is in direct contact with the skin. If you try this, make sure the metal plate is insulated from the skin.

UPDATE: A few people were asking where to buy a real Neurophone. The only model available new is the $800 NF3. The authorized dealers (as far as is known to us) are:

UPDATE: Maybe I wasn’t so far off after all. Neurophone inventor Patrick Flanagan has since confirmed the TL494 Pseudo-Neurophone design CAN produce Neurophone effects, though it’s still probably not as good as the real thing. Some research suggests this is why: the TL494′s square-wave output gets differentiated by the piezos (which are capacitors), producing a “Lilly wave”-like signal that mimics signals produced by nerves. (The Lilly Wave, as far as I understand, is a sharp positive spike followed by an equal but negative one. The idea is the first peak transports something, I think ions, across the barrier between nerves while negative spike brings them back so the nerves can use them again.)

UPDATE: I got it wrong! See the newest post. It turns out you have to replace the leading and trailing edges of the audio waveform with ones that have a 40kHz slope, and then double differentiate it. The TL494 Pseudo-”Neurophone,” while it does produce a tiny sliver of the real effect, is pretty far off.

UPDATE: It turns out “earplug-style” in-ear-monitor headphones produce some of (but probably not all) of the same effects a Neurophone does. Try playing pink noise through them! See the newest post.

By mixing an audio signal with ultrasound, you can hear the audio as if it’s inside your head… even if the ‘headphones’ are nowhere near your ears.

Patrick Flanagan invented the “Neurophone” over 40 years ago. His original patent (US3393279) was basically a radio transmitter that could be picked up by the human nervous system. It modulated a one-watt 40kHz transmitter with the audio signal, and used very near-field antennas to couple it to the body. It also used extremely high voltages.

Fortunately, we don’t need to work with radio transmitters or high voltages. Over a decade later, Flanagan came up with a version of the “Neurophone” that didn’t use radio, or high voltages. (Patent US3647970)

The second version of the “Neurophone” used ultrasound instead. By modulating an ultrasonic signal with the audio we want to listen to, it gets picked up by a little-known part of the brain and turned into something that feels like sound.

The weird thing is this works even if the ultrasound transducers are far away from the head: maybe down at your waist, or even further (depending on your body).

To make the ultrasound signal, we’ll use a widely-available TL494 pulse-width modulation controller. This isn’t a perfect solution, so you won’t hear the signal as well as with one of Flanagan’s designs. But it’s a lot simpler than messing around with DSP. And it gives you a chance to experience and experiment with the “Neurophone” effect.

Have a look at the schematic. You’ll see there are two adjustment potentiometers.

The first potentiometer is near the input, and it adjusts the DC bias of the input: whether the TL494 thinks the input signal is mostly positive, neutral, or mostly negative. The best way to adjust it is by connecting an oscilloscope to the circuit’s output. Connect a sine wave signal generator to the input. (If you don’t have a signal generator, generate a 440Hz sine wave in the open-source Audacity music editor and upload the file to an MP3 player.) You then adjust the potentiometer until the signal looks about even between top and bottom. If you don’t have an oscilloscope, try with the potentiometer centered.

The second potentiometer controls the modulation frequency. Using your oscilloscope or a frequency counter, turn it until you get about a 40-50kHz signal from the output (with nothing connected to the input). If you don’t have either of those, play with the control until you can hear the signal.

The ‘electrodes’ are actually transducers. You can pick up the piezo disks online, or at an electronics shop. Try searching for ‘piezo’ or ‘piezo element.’ You only need to connect to the piezo side on each: the disks form an electric circuit through the surface of the skin. (This may help the signal be heard, since nerves are sensitive to electricity too.) Don’t worry: there’s so little current flowing between the electrodes that you’ll feel nothing. (And while I’m not a medical professional, I don’t think there’s any way it could do any harm.)

Do be careful about putting them on and taking them off, though. They’re putting out a fairly high-power ultrasound signal, so if they sit too loosely on the skin they could irritate it.

Lastly, you’ll probably find the signal is easiest to hear ‘in your head’ with the electrodes near your head. Also, and this applies double if you’re putting the electrodes far away from your head, you’ll probably only be able to ‘hear’ a very narrow range of frequencies. A signal generator where you can easily vary the signal from 20Hz to 20,000Hz is very helpful in finding what you can hear and what you can’t.

Oh, and don’t forget to play with the volume control on your signal generator or MP3 player: you may need to set it a lot higher or lower than with regular headphones.ImageImage

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38 comments on “Make a “Flanagan Neurophone”-Like Device with a TL494

  1. Pingback: DIY Flanagan Neurophone lets you hear with ultrasound - Hack a Day

  2. Pingback: Indagadores |Seguridad informatica |Seguridad en internet » DIY Flanagan Neurófono le permite escuchar con ultrasonido

  3. Dias
    August 7, 2012

    Awesome, I’ve been thinking about making one of these the past month.

    Given the simplicity of the circuit, couldn’t most of the device easily be emulated with software, perhaps with greater sound quality?

    • neurophone
      December 17, 2012

      Sure. Probably better, even. See my newest post.

  4. Sheldon
    August 10, 2012

    Very cool. And just FYI, the type of piezo element you used is commonly called a “bender” and there’s a small trick to properly soldering them without damage as detailed here:

    http://www.digikey.com/Web%20Export/Supplier%20Content/PUI_668/PDF/PUI_bender_soldering_process.pdf?redirected=1

  5. Kerry Cartier
    August 13, 2012

    This article needs a circuit diagram that can be read, and a list of parts. Can’t try it if I can’t build it!

  6. Jordan Rose
    September 4, 2012

    Thanks for this! I don’t know if I’m technically minded enough to do this, but hopefully I can find a friend to help. I am also very curious, do you think there is a way to beef it up and make the signal stronger?

    • neurophone
      December 17, 2012

      Increase the supply voltage to the 40V maximum.

  7. biomedichim
    September 7, 2012

    Hi, I made this same circuit, although I get the right frequency output but i cant hear anything!!!! any advice??

  8. Walt
    September 8, 2012

    I just built the phone, but I’m not sure it’s working properly.
    On the plus side, as soon as both pads are touching my skin, I do hear music. And, when the pads are removed they stop working. However, I do not notice them behaving in any way differently from two piezos acting as speakers. The sound can be heard by someone standing nearby, and I don’t get the “in the head” feeling like a “bone phone” or other devices create.
    I also don’t notice any difference when I rotate the modulation frequency pot.
    I’d greatly appreciate knowing if this is correct operation for the device.
    Can someone standing nearby hear the piezos like speakers normally? Should there be some greater effect?
    Thank you!

    • neurophone
      December 17, 2012

      Yes, someone nearby should be able to hear them. You should be able to put the piezos some distance away from your head and still get the ‘sound in your head’ effect.

      • Walt Noon
        December 24, 2012

        Thanks. You’ve mentioned being able to get units from Flanagan. Would you be so kind as to post contact information? I’m very curious about the effect, but even after carefully scoping the phone I built, I get only as you mentioned “a sliver” of the effect. I appreciate your work though!

      • neurophone
        December 24, 2012

        Flanagan’s website is phisciences.com. He suggests buying them direct from his company Phi Sciences (+1 928-634-2668) for $800. They’re currently closed for the holidays, but will be open on January 2.

        It looks like the only Neurophone currently for sale was designed for Flanagan by a Bavarian engineer and is sold under the name NF3: http://neurophone.ca/products/ http://www.flanagan-neurophone.com/Bestellen/bestellen.html (German/European customers)

        There are also the GRS ($~250) and DSP ($~450), but I can’t find links to any site currently selling them.

      • neurophone
        December 24, 2012

        Also, if you’re good at building things, it’s apparently possible to build the circuit from Flanagan’s 2nd patent by replacing the transistor gain-stages with opamps. This would get you much closer than the TL494, but requires some electronics knowledge, and some way of driving the highly capacitative load that the piezos present.

      • Walt
        December 25, 2012

        Thanks very much for the info. Too bad Flanagan wants so much for them. It would be nice to try one, and see if it’s worth building from his second patent as you suggest. I’ve built a few devices from patents before, but have often found critical info is intentionally left out. It makes sense that someone would do that rather than allow others to follow their steps easily, but it has discouraged me from doing this as well. Thanks again!

      • neurophone
        January 5, 2013

        If you’re interested in a more advanced DIY design, T Bastian has a good compilation of designs here: http://home.dmv.com/~tbastian/nuroindx.htm

  9. Nick
    October 23, 2012

    The operation frequency of the TL494 is low which is possibly why our audio quality is low. Try something like a Max5069 and discrete driver mosfets and it might perform much better.

    • neurophone
      December 17, 2012

      Actually the low operation frequency is the only thing that makes it partly work. The slope of the output signal can’t be too sharp. See my newest post.

  10. Dick
    November 4, 2012

    hi i am not really handy with electronics.How much would you charge me to make DIY Neurophone for me?

    • neurophone
      December 24, 2012

      I don’t make Neurophones for anyone but myself. If you want ready-made, you’ll have to buy from Dr. Flanagan or one of his distributors.

    • Ian
      March 16, 2013

      If you still want a Flanagan Neurophone, I am selling mine at a discount. I only had it for 1 year. I made an upgrade so I don’t need this one. you can email me at finalresultsllc@rocketmail.com and you can buy it through paypal from my website

  11. addie
    November 27, 2012

    ca u give me the details of the peizo used !
    i made the circuit but cannot use it

    • neurophone
      December 17, 2012

      The piezo doesn’t really matter. Any piezo should work, the problem is probably somewhere else.

  12. freegen
    December 29, 2012

    Hi , this is interesting is it anywhere near puharich’s patent ? http://www.bibliotecapleyades.net/sociopolitica/esp_sociopol_mindcon11b.htm

    is there a way to make this work like a laser.. I read somewhere that something like this has been made to work from 100m distance!

  13. How did u actually obtain the concepts to post ““Make a Flanagan Neurophone-Like Device with a TL494 some electronic projects”?
    I appreciate it ,Verlene

    • neurogeek
      February 19, 2013

      I started with the patents that Flanagan filed and worked from there.

  14. Robert
    February 2, 2013

    If anyone is interested in purchasing an authentic Neurophone from an authorized seller, please contact buyneurophone@gmail.com for inquiries.

    • neurogeek
      February 19, 2013

      The post has been updated with your contact information.

  15. Steve
    February 5, 2013

    One can attempt to make a neurophone, but one truly cant reproduce the real one made by Gillis Patrick Flanagan. I was an electronics tech for yrs and use the neurophone everyday. The design internally has been refined over the years and I have done much research on it. After 2 weeks of using every night when I slept, I started remembering things such as peoples names and faces from when I was a kid that I could not recall in the previous years. I found that if I place the neurophone transducers on any part of the body that ached or bothered me, it was a miracle. My eye sight got better after 6 months and was was able to sleep thru the night for the first time in 10 years. My mother and aunt started using the neurophone and their depression lifted in a week. My aunt whom is hard of hearing placed the transducers near the ear using the neurophone and within a few weeks, her hearing was better. I didn’t have to yell when speaking. One can say all they want or disagree, but I know it works. I am a real estate appraiser by trade and my typing speed doubled and I am pumping out more appraisal reports than ever. It also has helped in many other ways. FYI-One can buy the latest neurophone in the US from an authorized patrick flanagan distributor by contacting neurophone1@gmail.com or contact@buyneurophone.com (same people). I understand they are setting up a website in the next month or so.

    [This post may have a commercial interest. -moderator]

    • gees
      February 19, 2013

      if it didnt cost a fortune someone could actually buy it…

  16. Brady
    March 6, 2013

    When I initially commented I clicked the “Notify me when new comments are added” checkbox and now each time a comment is
    added I get four e-mails with the same comment.

    Is there any way you can remove people from that service?

    Many thanks!

    • neurogeek
      May 26, 2013

      I don’t see a way. Are there any WordPress experts here that know how to do this?

  17. Pingback: Energy Science Forum

  18. Pingback: Neurophone(Flanagan) Schematics for Hearing through the Skin | Mark Zive

  19. Pingback: DIY Flanagan Neurophone Lets You ‘Hear’ Sounds Through Your Skin - Science & Tech | Tech wikiHow

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