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 the Arduino Leonardo as the main board. It's the best option I've found that doesn't come with pre-installed headers. This can be important if you're using both the Adafruit PowerBoost 500 Shield for battery power and the 2.8" TFT Touch Shield for control; the former Shield doesn't allow for the SPI pins to go through, and using those pins for the latter Shield can keep things from getting too complicated.

Of course, if you're using the Helmet version,...

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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 × Arduino Leonardo Or any other Arduino main board that comes without headers
  • 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 female headers and the power switch to the Power Boost Shield.
    • Soldering through headers to the Sound Processing Shield.
    • Soldering through headers (or female headers, if you aren't using the Power Boost Shield) and the 2x3-pin male header to the Arduino Leonardo.
    • If you're using the BLE SPI Friend, solder short male headers to its underside.

    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 (in the event you decide to add a Shield that uses it), 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
    Neckband (Throat version only)

    This step in the Instructions is practically a project in itself.

    The Throat version of this project requires something to hold the mike against the neck; this could be the collar of a costume, though in many (if not most) cases a neckband will be needed even if your costume has a high collar. I'm assuming here that you'll be using lycra (Spandex). Technically, any fabric with a good amount of stretch will do, but I think lycra will work best for most purposes. If something else such as stretch velour works better for you, then by all means go for it!

    Note that much of this is geared toward not only keeping the mike and speaker in place, but also keeping the whole system concealed and thus maintaining the "illusion" that this is what your voice actually sounds like. If you're not concerned with that, then don't worry about it.

    As written, this Instruction assumes that you're using the recommended components specifically:

    • Adafruit Small Enclosed Piezo w/Wires
    • Adafruit Mini Metal Speaker with Wires
    • 5-foot TRRS cable with plug

    If you're using anything different than the above -- including sewing the mike and speaker into a larger garment -- you should be able to adapt these instructions easily enough.

    Measuring the Neckband

    Measure the circumference of your neck, ideally going through the center of your larynx. This will be the length of the fabric you'll need your neckband. Since the lycra will need to stretch to hold firm, the seam allowance will shorten the band just enough to do this without choking you.

    The width of the band will be a minimum of 3"; this is enough to wrap around the speaker, plus a seam allowance of 1/4" on either side. Of course, you can always make it wider if you want to, especially if there's an in-character reason for it.

    Component Preparation

    When worn, the speaker should fit directly at the band's front and center, with the piezo mike to one side but still close enough to touch the larynx. At the same time, the ends of the wires will need to match up to connect to the cable. The Adafruit speaker and mike have wires of just the right respective lengths for most people. If that's not the case for you, then trim the length of one or the other until the fit is right.

    You may optionally also want to trim the length of the TRRS cable. (While I don't exactly recommend against doing this, I do prefer not to.) The easiest way to get the ideal length would be to measure from the larynx (where the speaker will be) to the place where the enclosure will be, along the line where you want the cable to run; then add 8.5 inches. With the 3.5 inches on the speaker wires, this will give you one foot of leeway.

    Once you're satisfied with the length, connect the speaker and piezo wires to the cable wires. I recommend soldering them and covering the work with shrink wrap, though if you have a different method that you've found works for you, go ahead. Remember to connect the red piezo wire to the tip, the black one to the shield, and the two speaker wires to the two rings (the wire colors in the cable can very according to manufacturer).


    The speaker should go at the exact center of the neckband, so determine where that is by measuring, folding, or whatever means you prefer (as long as it's exact). Lay down the fabric right-side down, and use a pencil to draw a line where that center is (don't worry; that'll be on the inside of the neckband, so it won't be visible). Set the speaker face-down in the center of that center line. Then sew a loop around both speaker wires at least five revolutions. If the speaker has mounting holes that your needle can fit through, sew it to the fabric through those as well, being as exact as you can to keep the speaker in the center.

    Once that's done, sew a similar loop around all four wires about 1/8" from the piezo. Don't make it too tight; the wires will need to be able to slide through the loop as the band stretches.

    You may then, if you wish, sew additional anchoring loops around the wire every couple of inches to the end, though again don't make these too tight. You'll want to allow the lycra to not only stretch, but release the stretch without catching or bunching. Whether you do this or not, though, run the wire to the end of the fabric.


    At this point, turn the lycra lengthwise right side to right side, so the components are still on the outside. Sew together the long edges with the above-stated 1/4" seam allowance (it's OK to use your machine this time). Then turn the band right-side out.

    At this point you may fix the centering of the speaker and piezo by reinforcing where they're attached with more hand-stitching, this time going through the other side. In any event, make sure that they're not wiggling around inside the neckband when you're wearing it!

    How you fasten the back is up to you. Lycra (and most other stretch fabrics) should stretch well enough over your head, so sewing the back together may work fine. Having the wires come around half the neckband's length may present its own problems, though, so you may choose to instead go with Velcro, hooks, snaps, or some other means. However you work it, be sure to leave plenty of stretch room for the wires -- and be careful that your needle doesn't penetrate them!

    Finishing Touches

    That's it. Anything further is optional, and will depend on the costume itself. You now have your costume's neckband!

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