Oblique incidence properties of locally resonant sonic materials with resonance and Bragg scattering effects
Yuan Bo (袁博), Wen Ji-Hong (温激鸿), Wen Xi-Sen (温熙森)
Vibration and Acoustics Research Group, Laboratory of Science and Technology on Integrated Logistics Support,National University of Defense Technology, Changsha, 410073, China; MOE Key Laboratory of Photonic and Phononic Crystals, National University of Defense Technology, Changsha, 410073, China
Abstract A locally resonant sonic material (LRSM) is an elastic matrix containing a periodic arrangement of identical local resonators (LRs), which can reflect strongly near their natural frequencies, where the wavelength in the matrix is still much larger than the structural periodicity. Due to the periodic arrangement, an LRSM can also display a Bragg scattering effect, which is a characteristic of phononic crystals. A specific LRSM which possesses both local resonance and Bragg scattering effects is presented. Via the layered-multiple-scattering theory, the complex band structure and the transmittance of such LRSM are discussed in detail. Through the analysis of the refraction behavior at the boundary of the composite, we find that the transmittance performance of an LRSM for oblique incidence depends on the refraction of its boundary and the transmission behaviors of different wave modes inside the composite. As a result, it is better to use some low-speed materials (compared with the speed of waves in surrounding medium) as the matrix of LRSM for designing sound blocking materials in underwater applications, since their acoustic properties are more robust to the incident angle. Finally, a gap-coupled LRSM with a broad sub-wavelength transmission gap is studied, whose acoustic performance is insensitive to the angle of incidence.
Yuan Bo (袁博), Wen Ji-Hong (温激鸿), Wen Xi-Sen (温熙森) Oblique incidence properties of locally resonant sonic materials with resonance and Bragg scattering effects 2013 Chin. Phys. B 22 074302
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