I often enjoy tapping my fingers on a surface, like playing an invisible piano. If I’m really feeling a beat I’ll play some surface around me like a drum.

So, my “physical computing fantasy device” is an electronic musical instrument that can be played by tapping a table or other surface.

Here are some prototype videos.

The first one is with a piezoelectric microphone plugged directly into my laptop. I have some software written in Processing that “listens” for a tap and triggers a sound.

The second has the piezoelectric microphone plugged into the analog input of an Arduino microcontroller.

I made a version with two microphones to try to localize one-dimensionally.

However, this version did not perform as accurately as I would like.

My current version listens for a “trigger” (activity above a threshold) on the two microphones and compares the time between them. Some suggestions I have received are to rectify the signal (so that polarity doesn’t affect the trigger), to compare the waveforms in software (this will require a faster ADC), or to localize using phase.