Design files and software for my parametric ultrasonic speaker.
Switch branches/tags
Nothing to show
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
hardware
software
LICENSE
README.md

README.md

Parametric Speaker

Ultrasonic sound has much smaller wavelengths than regular audible sound making it much more directional than a traditional loudspeaker system.

The inteference of the 91 ultrasonic trancducers creates a directed speaker effect with a very narrow FOV ob -30dB @ ~ 2-3 degree.

For more background information about the physics behind this: https://en.wikipedia.org/wiki/Sound_from_ultrasound

Hardware

Basically the speaker consists of a varible DC/DC converter and a MOSFET fullbridge. The DC/DC creates a variable bridge voltage, while the H bridge creates the actual 40kHz carrier signal.

For now, all the 91 Ultrasonic transducers are in parallel. In the future i plan to build an actual phased array, so stay tuned.

Software

So far, the firmware on the STM32 doesn't do very much. It's required to initialize all the components via I2C. It also controls a small I2C OLED display and reads some buttons for adjusting volume, frequency, etc.

It' written using mbed so far, unfortuantly this is very inefficient. I'll probably use libopencm3 in the future.