Imagine three people huddled in a circle so when one speaks, only one other hears. Scientists have created a device that works like that, ensuring sound waves ripple in one direction only.
The device, developed by scientists at ETH Zurich and the Swiss Federal Institute of Technology Lausanne, is made up of a disk-shaped cavity with three equally-spaced ports that can each send or receive sound.
In an inactive state, sound transmitted from port 1 is audible to ports 2 and 3 at equal volumes. Sound waves bounce back to port 1 as an echo as well.
When the system is running, however, only port 2 hears port 1’s sounds.
The trick is to blow swirling air into the cavity at a specific speed and intensity, which allows the sound waves to synchronize in a repeating pattern. That not only guides the sound waves in a single direction, but gives more energy to those oscillations so they don’t dissipate. It’s kind of like a roundabout for sound.
The scientists say their technique may inform the design of future communications technologies. New metamaterials could be made to manipulate not just sound waves but potentially electromagnetic waves too.
Please incorporate this technology into TVs so I don’t have to hear them through the wall.
There’s the LRAD (Long Range Acoustic Device). It’s directional, but there’s side/rear leakage. This seems to be fully directional and works via a different method. Or, at least, that’s my understanding.
The LRAD is a loudspeaker. This technology is more like rf electronics.