Study on Acoustic Metasurface Absorbing Wide-Band Sound

In the fields of mechanical engineering and architecture, suppressing the vibration noise is an important topic. Sound barriers are used to reflect the noise but are not effective in low-frequency sound waves in open spaces. Another method is using the sound-absorbing materials/structures. However, there are still many challenges with sound-absorbing materials and sound-absorbing structures. The sound absorbing materials have weak interaction with low-frequency acoustic waves resulting in inefficient dissipation of sound energy, and the resonant structures need large space to absorb low-frequency sounds. Thus more research is needed for the development of the low-frequency sound absorption technology. Metamaterials which attracted much academic attention recently are artificial materials consisting of some special micro-structures. Wave propagation in the metamaterial has some special properties which can not be observed in the natural media. These micro-structures are usually resonators of waves, and then metamaterials can modulate the propagation of waves with a wavelength of 10 to 100 times of the size of the micro-structures. Studies of applying metamaterials to absorb sounds then appeared later. The metamaterials are usually made of resonant cavities arranged on the surface of objects, and thus the metamaterials are also named “acoustic metasurface,” representing that a layer of micro-structure on the surface of the object can perform the properties of metamaterials. This project is based on the previous results of designing an acoustic metamaterial plate of Helmholtz resonators to absorb low-frequency sound. This project aims to extend the frequency range of high absorption coefficient in resonant cavities. Helmholtz resonators, quarter-wave tubes, and cavities with porous materials will be analyzed to design a thin plate which can absorb sound of the wide-frequency range. The work included numerical simulation, design and fabrication of specimens, and experimental measurements. Geometric sizes of resonator will be changed to study the effect on absorption. Then specimens of metamaterial plates will be fabricated. The frequency response of sound absorption will be measured to be compared with the numerical analyses. The study is expected to be valuable for isolating and controlling the noise from industry and living.

Project ID:PB10708-1258
External Project ID:MOST107-2221-E182-048