Matryoshka locally resonant sonic crystal

Abstract

The results of numerical modelling of sonic crystals with resonant array elements are reported. The investigated resonant elements include plain slotted cylinders as well as various their combinations, in particular, Russian doll or Matryoshka configurations. The acoustic band structure and transmission characteristics of such systems have been computed with the use of finite element methods. The general concept of a locally resonant sonic crystal is proposed, which utilises acoustic resonances to form additional band gaps that are decoupled from Bragg gaps. An existence of a separate attenuation mechanism associated with the resonant elements, which increases performance in the lower frequency regime has been identified. The results show a formation of broad band gaps positioned significantly below the first Bragg frequency. For low frequency broadband attenuation a most optimal configuration is the Matryoshka sonic crystal, where each scattering unit is composed of multiple concentric slotted cylinders. This system forms numerous gaps in the lower frequency regime, below Bragg bands, whilst maintaining a reduced crystal size viable for noise barrier technology. The finding opens new perspectives for construction of sound barriers in the low frequency range usually inaccessible by traditional means including conventional sonic crystals.

Coupling local resonance with Bragg band gaps in single-phase mechanical metamaterials

“…A more practical and promising solution are single-phase metamaterials, which have attracted increasing interest in the community [29][30][31][32][33][34][35][36][37][38], and in which both types of BGs have been shown to be present [39][40][41][42][43]. However, to the best of our knowledge, the conditions and physical mechanism of the coupling of Bragg BG with local resonances in single-phase structures has not yet been analyzed.…”

Liquid sensor composed of one-dimensional sonic Helmholtz resonator array

“…The periodic properties of 2D phononic crystals and HRs have also been discussed extensively; it has been proposed that these types of structures contained acoustic band gaps and that these band gaps could prevent sound waves from specific frequency regions from propagating inside the structures [22][23][24][25][26]. It was also indicated that the type of band gap that occurs in HR arrays was decoupled from the Bragg gaps [24]. However, the analysis with regard to the Bragg effect is not applicable in our case.…”

Development of an Acoustic Metamaterials for Aero Acoustic Noise Control

“…Since the density contrast of piezoelectric rods and Air is large, the shear stress and transverse waves inside the piezoelectric rods will not have significant contribution to the scattering of acoustic wave in the Air background, so the PWE method is acceptable, and scalar wave equation is adequate to describe the system (Elford, 2011); and thus, the acoustic wave pressure field rather than displacement is carried out to get the corresponding band gap for this system. In addition, the acoustic wave pressure field has Bloch form.…”

“…Where , ) where the v is the velocity at host and "a" is the lattice parameter (Elford, 2011), (Kushwaha, 1994).…”