Compact Voice Changer

An electronic voice changer that can fit in your pocket (or helmet, or bulky mask, or on your belt)

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Cosplay, Halloween, theater... there are many settings where it can be useful, or at least more fun, to match your costume with an appropriate voice.

This project takes the Sound Processing Shield (a separate project of mine) and applies it to the very reason I designed it: a voice changer that you can hide on your person.


There actually are three basic variations on this device, each with its own advantages and challenges, and each serving a different purpose.

Helmet Voice Changer

This is a version that could be used by a Stormtrooper or Mandalorian bounty hunter from the Star Wars setting; a Dalek or Cyberman from Doctor Who; Iron Man or some similar power-armored superhero; or similar things. (I originally conceived of it for a costume as the Golden Age Sandman, even though he never used one -- which should illustrate how you can go ahead get really creative with this!)

Among the limitations of this version is that its placement makes it difficult to control directly; a separate control of some sort will be needed. The solution presented here is to use an Android app to control the device via Bluetooth; while the Bluefruit app can suffice, I expect to be working up an Android app specifically for this project. (An iOS version is a big maybe.) It should also be possible to control the device through some other method, such as XBee or even a wired remote, though I'll leave these to the reader's creativity.

On the other hand, this version has the benefit of being completely self-contained: the microphone and speaker can be kept in the same enclosure as the electronics. Since the device will be very near the user's mouth, and probably directly in front, some protection will be needed to stop breath and spittle from contacting the mike and electronics, but those concerns are easy enough to address.

Throat Voice Changer

But what if your character doesn't wear a helmet, or any other kind of mask? What if your costume is as the Monitor from the "Arrowverse" TV show crossover events (Elseworlds and Crisis on Infinite Earths), or a Goa'uld System Lord from the Stargate franchise, or something of that sort? What then?

Well, hopefully you can cover up your neck, because that's where the piezoelectric microphone comes in handy. For this, you'll want something very small, and most importantly thin -- and that goes for your speaker as well.

You'll also be doing a bit of sewing; have some lycra (spandex) ready. If you prefer, you may use some other stretch fabric, but lycra will work best for most purposes. (If the neckband is going to be visible, make sure it's the right color! Unless it's going to pass as a decorative neckband, it should match either your skin color or the color of an adjacent garment.)

However, keeping the electronics separate does have the advantage of allowing the user to control the device's parameters right from the box itself. The (arguably) simpler method is to use a touch screen, though it could also be possible to use buttons, switches, and wheels (though I'll leave the implementation to your own creativity). Of course, Bluetooth control is still possible, and the device could even be set up to use both.

Hand-Held Voice Changer

This is the version that isn't hidden; it's just a completely self-contained unit. It can be used to experiment with settings, demonstrate the device, or just have fun at parties.

Since there's no need to keep up any "illusion," there's no need to hide any part of this. The enclosure can include the mike and speaker from the helmet version, and the touch screen from the throat version; everything you need is in one unit, without having to connect up anything else.


The heart of the project is the Sound Processing Shield, a separate project I've done here on Hackaday.

As listed,  the project uses Adafruit's Metro M0 Express as the main board, though you probably could substitute just about any Arduino Uno compatible board.

Of course, if you're using the Helmet version, you'll probably need to do without the screen, so Bluetooth control is recommended. While some Arduino-equivalent boards have Bluetooth built in and Adafruit has their BLE Shield, just in case those aren't viable the Sound Processing Shield has a place to plug in Adafruit's Bluetooth...

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  • 1 × Sound Processing Shield a separate Project on his site
  • 1 × Adafruit PowerBoost 500 Shield optional but strongly recommended
  • 1 × 2.8" TFT Touch Shield for Arduino with Capacative Touch for the Hand-Held version; an option for Pocket
  • 1 × Adafruit Metro M0 Express actually, any Arduino Uno compatible board will do
  • 1 × Adafruit Bluetooth LE SPI Friend optional, for control via Bluetooth

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  • 1
    Create the Enclosure

    This is the first item on the list because the enclosure will probably be 3D printed. You'll be able to work on most of the intervening steps while waiting for your printer to finish (especially if you're using a mail-order service such as makexyz).

    The download package includes several basic models are for the enclosure, and you may modify them as you wish. Those provided assume basic forms for the Throat, Helmet, and Hand-Held versions.

    The recommended forms are:

    • For the Helmet version, Internal/Bluetooth (but see below)
    • For the Throat version, External/TFT
    • For the Hand-Held version, Internal/TFT

    Of course, what works best in your specific case is up to you.

    For the Helmet version, if you're also 3D printing the helmet, you may wish to incorporate the voice changer's enclosure in your model. Otherwise, you should work out a place to mount the enclosure.


    Of course, if you're modifying the project, you should modify the enclosure to match. Use this checklist of changes to make sure you're covered:

    • If you're using any additional Shields (including a second Sound Processing Shield), you'll need to expand the enclosure, and add holes for any additional connectors, switches, etc.
    • If you're using the Sound Processing Shield 2 in place of the Sound Processing Shield 1 or vice versa, you'll need to change the plugs for the holes.
    • If you're using a larger battery than the current recommended 2000mAh (the largest size that will fit on the PowerBoost Shield), you'll need to create a separate space for it.
  • 2
    Solder the Headers

    This would be an ideal time to solder any headers to the Arduino boards. If you're using the listed parts, this would consist of:

    • Soldering through headers and the power switch to the Power Boost Shield.
    • Soldering through headers to the Sound Processing Shield.
    • If you're using the BLE SPI Friend, solder short male headers to it.

    While you have the Power Boost Shield on the soldering mat, this would be a good time to connect one of the Battery Voltage Monitor jumpers. The provided sketch assumes A1 is used, reserving A0 for any analog output, though you may use another pin if you wish. (If you want to omit this function, you'll need to "comment out" that part of the sketch, later.)

  • 3
    Ready the TFT Display Shield (optional)

    If you're using the TFT Display Shield, you'll need to work the solder jumpers.

    First, placing the Power Boost Shield between the main board and the Display Shield means that there's no way to pass the SPI connection through between the two; the regular digital pins must be used. Use a sharp knife to disconnect all three ICSP jumpers, and then connect the D11/D12/D13 jumpers.

    Also, there's no need for the screen to be on all the time, so the sketch allows it to be shut off when it's not being used (letting the device do its voice-changing work without the screen being on). To facilitate this, connect the "back lite"/#5 pin.

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