Feb 16, 2016 | By Tess

A team of researchers working at the French National Centre for Scientific Research (CNRS) and the University of Lorraine in Nancy, France have designed an acoustic metasurface capable of perfect sound absorption which could be fabricated using 3D printing technologies.

The design for the acoustic metasurface was developed by Badreddine Assouar a research scientist at CNRS, and Yong Li a post-doc researcher, and has been published in this past week’s AIP Puslishing’s Applied Physics Letters.

The article published by Assouar and Li describes their coil based acoustic metasurface which is capable of achieving total acoustic absorption in low-frequency ranges. What is particularly ground breaking about their work is that they’ve developed an extremely thin structure that absorbs sound with the same efficiency as a thicker acoustic absorber.

As Assouar explains, “The main advantage is the deep-subwavelength thickness of our absorber, which means that we can deal with very low-frequencies—meaning very large wavelengths—with extremely reduced size structure.”

Until now, acoustic absorption systems being used for low-frequencies required relative physical thickness to properly absorb large wavelengths, which are dissipated in their passage through specially designed air cavities. Now, however, thanks to the French researchers’ internal coil design, frequency absorbers, or soundproofers, could feasibly be made much thinner while having the same capabilities of a thicker sound absorber.

The design works by having sound waves enter the absorber plate through a small hole located in the middle of the tile. Thanks to the internal coil’s acoustic reactance, the sounds are absorbed through the perforated hole rather than reflected from the absorber’s solid surface. Once through the hole, the waves are forced to move through the coil, an almost maze-like structure, which lengthens the propagation of the sound waves and results in an effective low sound velocity and high acoustic refractive index.

Dealing with sounds and acoustics has not been easy however, and Assouad and Li have overcome many challenges. As they lay out in their report, “Constructing a perfect and stable acoustic absorber with deep subwavelength thickness is a challenge due to the intrinsically physical dissipation mechanism. By solving this hard challenge, our designed metasurface-based perfect absorber has intriguing applications and paves the way towards the related devices.”

While the acoustic metasurface is only a proposed design for the moment, Assouad and Li will soon get to work on creating samples of their design using 3D printing technologies in order to conduct performance analyses. “Our proposed structure can be easily fabricated with 3D printing technique and takes advantages of the compact size, stable structure, and high efficiency,” they explain.

While the proposed design will likely have applications within complex acoustic engineering processes, we can’t help but daydream about the 3D printed perfect sound absorber being used to muffle our noisy neighbour’s loud music. In any case, we'll be sure to keep an ear open for more developments within the project.

 

 

Posted in 3D Printing Application

 

 

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