Notes concerning “Ultrasound”

• A unicast phased-array ultrasonic “radio” 2013-05-17 (4 minutes)
• Passive ultrasound sonar 2016-12-28 (1 minute)
• Bubble display 2017-01-24 (updated 2017-08-03) (1 minute)
• The Bleep ultrasonic modem for local data communication 2018-12-10 (updated 2018-12-11) (8 minutes)