For this project I built a gun that shoots out a narrow beam of ultrasonic audio. The sound can only be heard by people inside the narrow beam, or through a nearby source when the audio gets demodulated.

I was inspired to build this project after watching CodeParades    / @codeparade   awesome video Turning Sound Into a Laser:    • Turning Sound Into a Laser  .
I definitely recommend watching his video before you watch mine.

Ive seen parametric speakers for sale but I wanted to make one on my own.
It works by taking an audio source, in this case a Bluetooth speaker circuit, which then gets modulated to 40khz through a 555 timer circuit. From the 555 timer the output gets amplified and then is then sent to an array of ultrasonic transducers.

40khz is outside of the audible human range which means we cant hear it, however once the sound waves strike an object, the 40khz sound gets demodulated and you can hear the sound that's playing over the bluetooth speaker module. Because you cant hear the ultrasonic sound, It makes it seem like the sound is coming from the object. If you stand in the narrow beam of sound waves the sound can be heard, but standing just outside the beam the audio is silent.

Full Build Instructions: https://www.hackster.io/ShaneB/ultras...

Song I used for playing over speaker: Dizzy - Joakim Karud [Vlog No Copyright Music]    • Dizzy – Joakim Karud (No Copyright Mu...  

Song playing in background: Moana - Ryan Little
   • Ryan Little - Moana [Chillhop/Hip-Hop...