Facebook filed patent for ambient audio system: Rejoice they said they will not use it

Now this seems curious. A company files a patent application for a system that it never intends to use. Why bother? Facebook, the company that filed, has its reasons but first let us see what the patent is all about. Facebook filed to patent a system that can remotely activate the mic on your smartphone using inaudible signals broadcast via a television.

source: https://techxplore.com/news/2018-07-facebook-patent-ambient-audio.html