[Lindsay] has a wonderful writeup about a new toy in the shop, an ultrasonic transducer. The 28kHz, 70W bolt-clamped Langevin transducer by itself is not much use, you need a power supply ...

John KingJohn King worked with the aerospace and safety industries. He invented an early warning sonic transducer in 1972. A sonic transducer analyzes sound waves to determine distances ...