When researchers from Bristol and Sussex universities in the United Kingdom began to develop new ways to reshape sound delivery, they turned to how optical systems work and two frequent staples of inspiration: Legos and 3D printing. The result is new metamaterials that have the potential to kick sound manipulation into the future.
“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,” said Dr. Gianluca Memoli, research lead and lecturer in Novel Interfaces and Interactions at the University of Sussex. “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.”
Like how light can be manipulated to light up an entire room or be narrowly focused like a flashlight, these new acoustic metamaterials can be pinpointed to a specific sound or amplified for everyone to hear. Its potential could be a game changer for the communications and entertainment industries.
“In the future, acoustic metamaterials may change the way we deliver sound in concerts and theaters, making sure that everyone really gets the sound they paid for,” said Letizia Chisari, research contributor. “We are developing a sound capability that could bring even greater intimacy with sound than headphones without the need for headphones.”
The team developed metamaterials that have no refractive index, allowing sound waves to be bent, shaped and focused while passing through. The metamaterials are 3D-printed into Lego-like bricks that can be put together to work like a converging lens for sound. Coiling of the bricks allows for sound waves to be slowed and transformed.
While only a few can be used, how they are assembled reshapes sounds waves in different ways. The researchers have configured it into a collimator, which works like an acoustic spotlight to deliver sound like a spotlight beam, and a magnifying glass, which can zoom in on a sound from a distance.
“Using a single speaker, we will be able to deliver alarms to people moving in the street, like in the movie Minority Report,” said Jonathan Eccles, University of Sussex computer sciences undergraduate student. “Using a single microphone, we will be able to listen to small parts of a machinery to decide everything is working fine. Our prototypes, while simple, lower the access threshold to designing novel sound experiences: devices based on acoustic metamaterials will lead to new ways of delivering, experiencing and even thinking of sound.”
Although the project is in the early stages and the team has yet to determine a large-scale technique, the researchers believe their findings could be beneficial in an array of applications including high-intensity ultrasounds for destroying tumors, pinpointing triggered alarms and 360-degree theater coverage.
Interested in more ways researchers are exploring sound technologies? Check out Altering Sound Waves Could Make Objects Invisible to Sensors.