[itissid]

Wonderful. ultrasonic range emission having high S/N is amazing too. My hero usecase for this is to use these for behavioral therapy: Have a ring or a bracelet, thus without reaching for a phone or a notepad, record when a negative thought happens, i.e. a counter, or generate a sequence of ultrasonic sounds to map to specific kinds of thoughts. Have a sensor record and log them. I would then analyze the data across multiple days. My current method is recording them in obsidian.

[rustyhancock]

If you're old enough you might remember the Zenith Space Commander (I'm not old enough to have seen one in use).

It was an early TV remote that used spring loaded strikers controlled by buttons on the remote. The strikers hit tuned metal bars that rang out at ultrasonic frequencies the TV detected.

A links below but honestly it's the kind of topic that seems to never be covered well by a single resource. There are YouTube videos showing the inside of the controller and the striker.

[0] https://forums.atari.io/topic/10559-zenith-space-command-vin...