Acoustic wave filtering strategy based on gradient acoustic metamaterials

Acoustic metamaterials possess fire-new capacities to manipulate the reflected, refracted and diffracted wave wavefronts effectively and flexibly through designing special artificial structures. In this paper, a transmission-type phase gradient metamaterials with high efficiency transmission and variations phase shift covering a full range of 2 pi was reported. Capacities of manipulating transmission angle using the designed acoustic metamaterials were expected to be realized under the guidance of the generalized Snell's law. An acoustic filtering strategy occupying the selective permeability for the desired transmitted frequency were theoretically and numerically presented. Furthermore, a multi-channel filtering strategy was also designed and demonstrated. The results verified that the devices were highly sensitive to the incidence frequency and the transmission coefficients over 0.7 can be obtained at the working frequencies. The provided devices show an overwhelming promise of applications in various situations, such as architectural acoustics, acoustic logical manipulation, noise control, ultrasound imaging and multifunctional materials.