Metamaterial manipulates sound for targeted audio

A material that can bend, shape and focus sound waves that pass through it could have applications in highly targeted audio, ultrasonic haptics and medical imaging. Teams from two UK universities developed the material and demonstrated its application with sound waves in a paper titled ‘Metamaterial bricks and quantization of meta-surfaces’.

The Universities of Sussex and Bristol worked together on the system that can create finely shaped sound fields which have use in medical imaging, audio spotlights and ultrasonic haptics. The materials approach taken by the researchers is simple and cheap compared to alternatives. 

By assembling a metamaterial layered out of lots of small bricks that each coil up space the team was able to slow down sound. Therefore incoming sound waves could be transformed into any required sound field.

Large versions of the demonstrated system could be used to direct or focus sound to a particular location and form an audio hotspot. The layer could be fitted to existing loudspeaker technology and be made rapidly and cheaply.

Dr Gianluca Memoli, from the Interact Lab at the University of Sussex who led the study, said: “Our metamaterial bricks can be 3D printed and then assembled together to form any sound field you can imagine. We also showed how this can be achieved with only a small number of different bricks. You can think of a box of our metamaterial bricks as a do-it-yourself acoustics kit.”

Professor Sriram Subramanian, head of the Interact Lab at the University of Sussex, added: “We want to create acoustic devices that manipulate sound with the same ease and flexibility with which LCDs and projectors do to light. Our research opens the door to new acoustic devices combining diffraction, scattering and refraction, and enables the future development of fully digital spatial sound modulators, which can be controlled in real time with minimal resources.”

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