Scientists Design Acoustic-Based Focal Lenses Using Metamaterials to Transmit a Beam of Sound

Researchers from the University of Sussex and the University of Bristol have designed acoustic focal lenses created from metamaterials, as well as a collimator that can focus sound in a narrow directional beam generated by a standard speaker. Think of it like an acoustic ‘spotlight,’ where sound can be targeted on specific points. For example, imagine hearing the nuances of every instrument at a concert, but instead of being in the front row, you’re seated at the back of the arena.

The researchers dubbed their new technology Vari-Sound and developed the platform using metamaterials created from common materials. According to Dr. Gianluca Memoli at the University of Sussex:

“Acoustic metamaterials are normal materials, like plastic or paper or wood or rubber, but engineered so that their internal geometry sculpts the sound going through. 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.”

As mentioned earlier, the Vari-Sound platform was built using metamaterials — in this case, plastic, which is fabricated with an internal structure designed to control, direct, and manipulate sound. Each is made up of cells — a collection of sub-wavelength structures capable of managing those sound waves in terms of phase and intensity. Those cells are then combined into larger 3D structures to form an acoustic lens.

Those lenses are attached to a collimator that can adjust them to different focal lengths (using an Arduino Nano and stepper motor mounted to an adjustable rail) to beam sound from a regular speaker to the desired point. The researchers offer plenty of applications for the Vari-Sound device, including using it to detect fatigue in machine parts, identify and pinpoint different sounds (i.e., burglars breaking your window, where gunshots originate from, etc.), and upgrade personal assistant devices like Alexa that could hear commands from various locations in the home. Of course, that’s beside the obvious use case for home entertainment systems, which could bring headphone quality surround sound without needing the headphones.