Beware of ads that use inaudible sound to link your phone, TV, tablet, and PC

2015 article. Something more relevant might be facebook getting a patent to control your phone via tv audio.<p><a href="https:&#x2F;&#x2F;metro.co.uk&#x2F;2018&#x2F;06&#x2F;22&#x2F;facebook-wants-hide-inaudible-messages-tv-ads-force-phone-record-audio-7652112&#x2F;" rel="nofollow">https:&#x2F;&#x2F;metro.co.uk&#x2F;2018&#x2F;06&#x2F;22&#x2F;facebook-wants-hide-inaudible...</a>

What counter-measures exist? (e.g. an audio detector listening above 20 kHz?)