But a hackier way would be to build a parametric speaker that focuses soundwaves into a narrow beam like [Shane] did with this ultrasonic ... he fried a cheap Bluetooth audio module while trying ...

With a standard old HC-SR04 ultrasonic sensor, an audio module and a servo to drive a custom gauge needle he’s made a device which can warn people around you if they’re too close for comfort.

ams announced the availability of a new module which provides a complete hardware and software blueprint for an ultrasonic flow sensor, the key element of the next generation of long-life, low-power ...