Alphajammer - What is a parametric speaker? 🔊 Experiments with parametric and directional speaker systems have been going on since the early 1960s. Ultrasonic sound has much smaller wavelengths than regular audible
These directional speakers throw sound in focused beams like a spotlight - Yanko Design
Pack Hypersound - Waves system
Brown Innovations Directional Audio - Sound Dome Directional Speakers
Compact Ultrasonic Directional Sound Speaker for Home and Museum - China Ultrasonic Speaker, Directional Speaker | Made-in-China.com