Tunable transmission spectra of acoustic waves through double phononic crystal slabs

Abstract

Acoustic resonant modes in a slab with a periodic array of holes are analyzed by using three-dimensional finite-difference time-domain method. We show that there exist two different types of resonant modes in this slab: the coupled Stoneley wave resonant modes and the waveguide resonant modes. Both resonant modes can lead to complex resonant line shapes in the transmission spectrum. By using the distinct property of these resonant modes, a tunable phononic crystal structure consisting of coupled phononic crystal slabs is introduced for achieving acoustic filters and sensors.

Extraordinary Sound Screening in Perforated Plates

“…In real solids deviating from the hard-solid limit, sound can penetrate and is not attenuated exponentially like light inside a metal. Also the existence of surface waves in the plate (leaky Lamb waves) and interface waves [21] (Scholte waves) between the plate and the fluid can play an important role in the sound propagation, especially if the incidence direction is not normal to the plate. Our sound transmission study would be analogous in that instance to optical transmission through holes in dielectrics of high index of refraction.…”

Ultrasonic transmission through periodically perforated plates

“…This phenomenon has been already proposed in [151,69] to explain transmission features predicted [151] measured [69] in periodically corrugated brass plates immersed in water both at normal incidence, though no direct proof has been given yet.…”

“…The flexural coupling was as important as the random incidence and the high TL obtained in Kundt tube experiments could not be repeated in transmission chamber ones. The theoretical predictions under the rigid-solid assumption [151,59,60] propose a double layer of periodically perforated structures, although no realistic comparison neither with single wall nor with double homogeneous wall are given.…”

“…In addition to ρ and c , which define the characteristic impedance z 0 , also the transverse wave velocity c t in the solid needs to be taken into account. In these calculations it is chosen as c t = 0.7c l / √ 2, thus satisfying c .8, c t /c 0 ≈ 2) and the theoretical prediction in [151] for PMMA perforated plates in water (K ≈ 1.8, c t /c 0 ≈ 0.7) (see appendix B.1 for more details).…”

“…Other approaches using periodic structures having air resonant cavities have been proposed [155,151,59,60]. Hannink et al [155] attempted to build a thin shell structure for airborne sound insulation purposes by means of λ/4 resonator (hole closed at one end).…”