Researchers at Penn State invented hypertargetable audio that doesn’t require any equipment to be worn by the receiver https://futurism.com/sound-audible-enclaves

It’s easy to jump to military applications for this (disguise the sound of gunfire! confuse and manipulate your enemy!) but I think it’s more likely it gets used for advertising first

The Farcaster formerly known as Kchamp. Books, beats, bodybuilding, bright ideas and beautiful things.

katherinechampagne.com

Jokes on them we all wearing noise cancelling airpods.