Use your ears as an oscilloscope

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When work on an engine control circuit [Scott] found himself in need of a way to compare the performance of two control circuits at once. The hobby quality oscilloscope he owns wasn’t up to the task. After thinking about it for a bit he ended up using his ears as the oscilloscope.

The signals he was measuring are well suited for the challenge as they fell within the human range of hearing. He used some wire wrapped around each of the three conductors on the jack of his headphones in order to connect them to a breadboard. Then he simply connected each channel to one of the motor driver circuits, and connected the common ground. Listening to the intonation of the pitches in each ear he was literally able to tune them up.

If he had been looking for a specific frequency he could have used his sound card to take and analyze a sample. But balance was what he needed here and you must admit that this was an easy and clever way to get it!

Comments

  1. Christopher says:

    Rather clever, but I believe he could have mixed both signals into his oscilloscope and just tuned them based on constructive/destructive interference or beat frequency.

    • cooperised says:

      Yep, or stuck it in X-Y mode and tried to dial in a straight line.

      • simcop2387 says:

        Might not have been possible on that one, he says his osc was only one channel. Still doable I would imagine since you could take a snapshot and measure things and then compare them.

        • Password says:

          I have the exact same scope and indeed it does not have an x-y mode and onle one channel, but it can easily take a sanpeshot of a sample and you can display it as a reference.

          • Indeed, can’t do the X-Y. I can’t work out how to get the images off that scope, can you do it directly through USB or I need to use a micro SD card? I bought the scope off someone for cheap.

            This method of listening to the signals is really great, you can instantly tell if things sound right and even pick up things which are much harder to notice on a scope (especially these cheap ones), like random irregularities or missing beats.

    • Eric says:

      You can hear a beat frequency and null it out by putting one signal into each ear. Us broadcasters do this all the time to make two separate audio delay circuits match in timing, you can invert one of them to make it easier as they cancel completely ‘in your head’ when matched.

  2. echodelta says:

    Essentially what he is doing is tuning one circuit’s variable to the established reference of another. He’s doing that in binaural! Our hearing goes from 800 micro-seconds down to 0 of phase sense!
    Tuning a musical instrument with a snapshot approach will take lots of time. Come to think of it some guitarists I know seem to do that. It’s a realtime event that integrates error into a sort of PID and arrives very quick at the answer. Try playing steel guitar or the violin family. Or just sing. Or sync twin engine planes.

    • Eirinn says:

      Many professional guitarists can tune their guitar in seconds, usually only needing to twist the tuning knob once for each string. It’s really impressive.

    • Daniel says:

      The human ear is an incredibly accurate measuring instrument. Singing and playing guitar/piano for most of my adult life I can vouch for this. Picking up when someone is singing (or playing an instrument) “flat” is not all too difficult. Perfect pitch is completely optional.

      When listening for a difference in frequency by using the binaural method as mentioned, I was able to pick up a 1Hz difference. Using audacity, I send 440Hz to my left ear and 441Hz to my right ear.

      The ear is truly a seriously amazing tool to have!

    • Blue Footed Booby says:

      I played cello back in my school days. When I first started playing back in elementary school my teacher had us all practice humming an A until we could do it at will. From there you play each string with the previous one and tune until the interval sounds right. I can’t explain what it sounds like but it’s really, really obvious in a way that “is it the right pitch?” isn’t for most people.

  3. Brian says:

    This makes me think of Whistler from Sneakers

  4. Erik Johnson says:

    I’ve done something similar a few years ago in the field; a uC seemed not to be working and I had no scope to check for signals on the IO, and an LED is all fine and well to see power, but not that it is pulsing/emitting data in any fashion. I did have earphones for my phone… So I took a resistor and cliplead, clipped the ground and twisted the resistor around the earphone plug tip to use as a probe. Now I could hear any modulation/data and trace the break in signal. It really helped and I fixed it! The show went on…

  5. I’ve been using this trick for year. It works great for lots of circuit types!

    I also am fond of using a magnetic pickup with an amp and headphones to listen to circuits passively. You can actually hear data flowing around inside PCs and tell if components are running or not. Cyber stethoscope!

    • MrX says:

      That is a really nice idea! With a few more electronics one could scale any frequency that is picked up into the audible frequency range.
      What kind of amplifier are you using? Can you give more details? Thanks!

  6. echodelta says:

    Oh! Forgot to say focus an analogue TV camera on a vertical lines pattern by listening to the loudest “zing”, of the video as audio. Great for remote camerae focusing, no monitor needed!

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