Alunperin luin tästä Tieteen kuvalehdestä, joka tässä tapauksessa tarjoaa koko artikkelin myös Netissä.

"We've heard hypersonic sound. It could change everything." [Popular Science]

Mitä se on? Lyhyesti:
"Unlike ordinary speakers, which disperse sound in all directions, American Technology's speakers emit ultrasonic frequencies in a focused cone, like a flashlight. Only when you disrupt the sound beam or reflect it off a surface do you hear it. So audio can be pinpointed to reach an individual or widened to target a larger group."