The Autotuned Kazoo No One Has Been Waiting For
You literally can't go wrong with this autotune-enabled kazoo that corrects your terrible, off-pitch humming that no one wants to hear.
If you want to get a group of music aficionados all stirred up, bring up autotune. This audio processing system measures a singer’s vocal pitch and uses processing software to correct it so that they can never go off-key. Some people love the effect, while others believe it completely ruins a musician's natural singing voice, or is little more than a crutch to help poor singers sound better.
Engineer and hardware hacker Guy Dupont is a fan of autotune and thinks that the effect should be used well beyond just vocal correction. So Dupont decided to build an unlikely instrument — a kazoo with a built-in autotune-like system.
For those unfamiliar with how a kazoo works, the musician vocalizes into one end of the instrument. This causes a membrane at the top to vibrate, which in turn creates a sort of buzzing sound. The pitch it produces is controlled by the musician’s pitch, so going off-key will not produce a very pleasing result. At least not without Dupont’s autotune.
The basic plan involved using a microphone inside the kazoo to capture the musician’s humming, a microcontroller to correct it, and a speaker to vibrate the kazoo’s membrane with the corrected note. As it turned out, this did not work very well at all. The microphone and speaker were too close together, resulting in feedback. Furthermore, putting a microphone in a plastic tube is no way to get a good audio sample — it could only pick up poor quality, ringing sounds.
After a bit of thinking and trial and error, Dupont decided to move the microphone directly in-mouth to avoid these problems. Also, the kazoo’s membrane was removed such that sound could come directly from the speaker itself. With these alterations the kazoo was not really a kazoo anymore, but the sound was much better.
It was still not quite kazoo-like enough, however. So Dupont added buzzy harmonics in the processing algorithm, and also cheated by always generating a sawtooth wave that simply matched the frequency pitch detected by a YIN fundamental frequency estimation algorithm.
The hardware consists of an I2S MEMS microphone that was encased in foam and a 3D-printed case before getting a layer of hot glue to seal it for in-mouth use. This was wired to a Seeed Studio XIAO development board with an ESP32-S3 microcontroller that was hidden inside the kazoo. Also included was an amplifier, speaker, and rechargeable lithium-ion battery.
Should you tire of the kazoo sound, the instrument can also be used as a wireless MIDI controller for just about any synthesizer. It may be a bit of an oddball device, but it does look like it would be fun to play around with. Be sure to check out the video for some demonstrations of the kazoo.
R&D, creativity, and building the next big thing you never knew you wanted are my specialties.