Ultrasonic insulation using a Helmholtz-like phononic crystal with a slight filling factor

Metamaterials are artificial materials designed to control and manipulate waves. They present the advantage to prohibit acoustic propagation in some frequency ranges called Band Gaps. In this paper, we present a series of Helmholtz-like resonators shaped for ultrasonic insulation purposes. This host plate is made of silicon in which the unit cell represents a phononic membrane formed by a sub-wavelength aperture and two Helmholtz resonators facing each other and immersed in water. The finite element simulations are performed between frequencies 1.7 MHz and 2.95 MHz. It is shown that such configuration exhibits a large band gap exceeding 1000 kHz and an attenuation up to -35 dB.