It sounded unbelievable to me, but I did recall reading about it before. I don't remember where, but some Googling brought up this paper: On Covert Acoustical Mesh Networks in Air Just because you're paranoid, don't mean they're not after you? Also, cheers.
Proof of concept and deployment are very different things. Ultrasonic transducers are commonplace, ultrasound-capable speakers are rare, consumer gear capable of hitting those frequencies without heinous harmonics down where you can hear them are a figment of the imagination. It's the equivalent of saying that your smartwatch can beat Deep Blue at chess because after all, they're both computers. Also, cheers. Let's see if this shit works over EDGE. 
Many many years ago, my father decided to take us off-roading in our Laredo after church in the UP of Michigan. Way back into a two rut, we came across a puddle, maybe 20 feet long. My mom tried to talk him out of it, but he went for it. We bottomed out. We spent the next hour jamming branches under the tires in our Sunday best. Ready to go, we climbed in, and the jeep wouldn't start. My brother and my dad then went for help. A long time later, they returned with an old timer that quickly found a loose connection, I think it was the distributor, but I can't recall. We then rolled right out. My mother was not pleased.