I could see this being an option for a car. Imagine embedding this in a headrest so passengers could listen to something different from one another.

How is this even remotely new?

There have been patents on it since the 90's. A company was trying to commercialize "Silent Sound" back then.

For example:

US6052336 Apparatus and Method Of Broadcasting Audible Sound Using Ultrasonic Sound As A Carrier (Ultrasound) Lowery 1998.

Holosonics has been selling such systems for a while:

https://www.holosonics.com

Exactly. They have invented something old.