Electronic Stethoscope


[Vik] sent in this simple little project. He purchased a $3 spy ear, a simple 3 transistor amplifier, and attached a stethoscope end. Little modification was necessary, mainly just scraping a bit more space in the microphone tube. The end result is a super cheap electronic stethascope that can be hooked to a computer or other speakers for multiple people to listen to.

35 thoughts on “Electronic Stethoscope

  1. hmm, this is especially interesting to me as i’m considering going into bio/biomedical engineering.

    i can’t help but wonder though if there’s a better way of doing this. for example could you put some sort of microphone in the chest piece itself, and then just run wires (with no tubes anywhere) to the output device?

  2. maybe because the original version is even cheaper, does not require batteries and is even more reliabil and lightweight ;)
    but there are electrical stethoskops with more features than just amplification.

  3. @matt: you need the chest piece because the large movable surface and surrounding lip cuts off external sounds. If you did this with an unmodified spy amplifier it wouldn’t work as well, because ambient noise would get in the way.

    try wiring a medium sized speaker to a spy amplifier toy, the speaker would serve the same purpose as the chest piece, and it would be easier to create.

  4. I think, for practicality, I would have gotten some surgical tubing, or similar tubing for more separation between the stethoscope and the amplifier to keep the amplifier off of the “patient” or other item to be listened to. If it is something mechanical, I don’t think I would want outer vibrations to be picked up by the case and amplified as well. Other than that, the concept is excellent.

  5. Absolutely use a piece of tubing and de-couple that thing from the mic to reduce the creaking that case will do if you try to use it as-is.

    Isolate them thar mics boyos!

  6. Be careful adding long tube extensions. They knock on things too, and convery the “wump!” nicely to your ears.

    I’m hoping to end up with something I can stuff in my top pocket, pull out and use instantly. Hence the search for a retractable set of earphones with in-ear buds on.

    Stethoscopes are fine for wandering around wards with, but when you rush into the bush or worm into a car wreck, you don’t want to have the thing around your neck.

    I’ll keep a spare battery in the same pocket, and there will always be a standard stethoscope in the trauma bag anyway.

    If it works in practice, I’d like to add some filtering; selectable low and high filters for listening to heart or chest sounds. Maybe even print it on a RepRap now we’re getting printable conductors.

    Vik :v)

  7. Wait a sec, this hasn’t been done before? This sounds like the kind of thing that should have been not just built, but put into service in hospitals years ago. I gotta make one of these…

  8. when you amplify something, you increase noise as well as useful signal, so this unit let you hear actually less than regular one. Same as with antennas, ear is the best amp.

  9. Heh…

    This was my final year engineering project. Made an electronic stethoscope with a datalogger on the other end and recorded the sounds. The idea was for training, you could demonstrate the sound of an arrhythmia to a entire class of students so they knew what to look for. You could map it visually and hear the playback to help comprehension. Plus your GP could keep a record onfile so they could compare your heart patterns over your lifetime, thought you might be able to predict things eventually (with enough data). Think I got it all down to under $20AUD. Then I graduated and went into mining & resource engineering…

  10. yours truly did medical electronics BSc, needless to say isolation is paramount! i’d have used a small 1.2v battery powered read amplifier and an optical fibre based coupler just to make sure..

    also this approach may work well with some QTC (quantum tunneling composite) as the sensor, as the resistance change is fairly linear and immune to mains noise.


  11. “Wait a sec, this hasn’t been done before? This sounds like the kind of thing that should have been not just built, but put into service in hospitals years ago. I gotta make one of these…”

    …made one of these a long time ago (1st year at medschool) thinking the same thing… in reality they are less practical than a stethoscope. Earphones tend to tangle up, especially when rushing between patient. The beforementioned battery aspect is valid too. Another aspect is that you need to disinfect these after each patient (otherwise you tend to transfer nosocomial diseases to your weakest patients).

  12. I too thought this idea sounded familiar, then I remembered this article from 2007

    I’ve got a couple of those Spy Ear thingamajigs I bought many years ago intending to find a parabolic dish to make a homebrew long distance listener but never got aronud to it so they’re still in their packets.
    Now I need a stethoscope as well as a parabolic dish for projects I’ll never get round to finishing ;)

  13. “why dont doctors use them more? because the medical equipment company can sell them a simple tube for $350”

    No, you can buy a high quality stethoscope for 35.00. It just doesn’t come with the word “Lxxxxxx” on it.

  14. this is too old technology, gov or PI use laser to detact your speech. easy, can do it very far away, as long as temperate does not vary a lot. and crystal clear, can be used as court evidenc, do not get caught easily. Why use this old design. Or use a Bonic ear can do the job as well.

  15. Hello I`m telecommunication Engineer doing the research in combine Electronic Stethoscope and Thermometer for Rapid Diagnostic Test (CEST-RDT) so I fine some difficult in the screen LCD display because I`m using Nokia 3310 LCD to display the temperature and pulse is no working and I use the computer to display the information true the USB to the computer and the frequency of heart bit in the oscilloscope to see the frequency for the heat bit.

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