Turtle Beach have announced the worlds first transparent directional speakers at E3 2016. "Opening the doors for exploration into several future directional audio products and glass applications in the consumer, commercial and hearing healthcare spaces."
HyperSound Video (https://youtu.be/4cd3Pm7XIZI)
I've heard such directional panels (not transparent though .. but who cares), which output ultrasound and believe this to be the case here too, a few years ago. It was not hi-fi by a long shot, but it worked .. best outside. ;)
Well that's certainly unnerving. My paranoia leads me to believe there's going to be an increase in the number of high profile individuals being diagnosed with mental disorders.