Academics from the University of Sussex and their colleagues at the University of Bristol demonstrated how they used acoustic metamaterials to control sound like light.
Their metamaterial device was able to zoom in on a single person. It was developed alongside a collimator that sent sound from an ordinary speaker in the form of a directional beam.
Their technology made it possible to make directional speakers that might target one person in a heavily populated area. The acoustic telescope may see use in the entertainment industry and as a method of communication in public.
It may also get misused as a psychological weapon to drive victims insane by making them hear voices that only they could hear. (Related: New metamaterial can silence sound.)
New acoustic telescope may send sound-based messages to an individual recipient over distances
Sussex researcher Dr. Gianluca Memoli explained that acoustic materials used conventional ingredients, like plastic, paper, rubber, or wood. Engineers designed the materials so that their internal structure shaped the sound passing through them.
“The idea of acoustic lenses has been around since the 1960s and acoustic holograms are starting to appear for ultrasound applications, but this is the first time that sound systems with lenses of practical sizes, similar to those used for light, have been explored,” explained Memoli.
His team worked with ordinary materials. They shaped the surfaces to control, direct, and manipulate waves. By engineering metasurfaces in a certain way, the researchers got a material to act like converging lenses for sound-waves.
There are various ways to use an acoustic telescope. It might employ a sound lens as a receiver for pinpointing suspicious sounds.
When installed inside a machine, an acoustic telescope will listen for the audible cues of mechanical problems. As part of a home security system, it will differentiate between harmless noises and the sounds made by a home intruder.
The acoustic technology may also enable 360-degree sound coverage in entertainment activities like concerts and movies. So, no matter where an audience member sits, he will enjoy the listening experience.
“In the future, acoustic metamaterials may change the way we deliver sound in concerts and theatres, making sure that everyone really gets the sound they paid for,” explained Sussex researcher Letizia Chisari. “We are developing sound capability that could bring even greater intimacy with sound than headphones, without the need for headphones.”
Another piece of technology leading to the world of The Minority Report
The acoustic telescope promised to take the auditory experience of the listener to the next level. Its capabilities exceed those of current entertainment systems that use phased arrays.
The surround sound system of a movie house or home theater has a sweet spot. Outside of that area, the quality of the auditory experience goes down.
Meanwhile, audio spotlights cost a lot of money. They only send low-quality sounds.
Likewise, the acoustic lenses in ultrasonic transducers and home audio systems are much bigger than some wavelengths. The devices only work for the upper end of the acoustic spectrum.
Compared to these phased array devices, acoustic metamaterials cost less, take up less space, and require simpler manufacturing processes. It is even possible to make them out of recyclable materials.
However, Sussex researcher Jonathan Eccles cited The Minority Report, where people received alarms while their neighbors didn't hear anything. It might be possible for the acoustic telescope to send ominous messages to a person or make him think he can hear voices inside his head.
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