[JoshMnem]

Also used for other purposes. Consumers would never consent to it if they understood it.

https://www.wired.com/2016/11/block-ultrasonic-signals-didnt...

https://arstechnica.com/tech-policy/2015/11/beware-of-ads-th...

https://www.theatlantic.com/technology/archive/2015/11/your-...