1,819 research outputs found
Subwavelength sound screening by coupling space-coiled Fabry-Perot resonators
We explore broadband and omnidirectional low frequency sound screening based
on locally resonant acoustic metamaterials. We show that the coupling of
different resonant modes supported by Fabry-Perot cavities can efficiently
generate asymmetric lineshapes in the transmission spectrum, leading to a
broadband sound opacity. The Fabry-Perot cavities are space-coiled in order to
shift the resonant modes under the diffraction edge, which guaranty the opacity
band for all incident angles. Indeed, the deep subwavelength feature of the
cavities leads to avoid diffraction that have been proved to be the main
limitation of omnidirectional capabilities of locally resonant perforated
plates. We experimentally reach an attenuation of few tens of dB at low
frequency, with a metamaterial thickness fifteen times smaller than the
wavelength (lambda / 15). The proposed design can be considered as a new
building block for acoustic metasurfaces having a high level of manipulation of
acoustic waves.Comment: 7 pages, 8 figure
Wave mitigation in ordered networks of granular chains
We study the propagation of stress waves through ordered 2D networks of
granular chains. The quasi-particle continuum theory employed captures the
acoustic pulse splitting, bending, and recombination through the network and is
used to derive its effective acoustic properties. The strong wave mitigation
properties of the network predicted theoretically are confirmed through both
numerical simulations and experimental tests. In particular, the leading pulse
amplitude propagating through the system is shown to decay exponentially with
the propagation distance and the spatial structure of the transmitted wave
shows an exponential localization along the direction of the incident wave. The
length scales that characterized these exponential decays are studied and
determined as a function of the geometrical properties of the network. These
results open avenues for the design of efficient impact mitigating structures
and provide new insights into the mechanisms of wave propagation in granular
matter.Comment: submitted to Journal of the Mechanics and Physics of Solid
Lagrange Model for the Chiral Optical Properties of Stereometamaterials
We employ a general Lagrange model to describe the chiral optical properties
of stereometamaterials. We derive the elliptical eigenstates of a twisted
stacked split-ring resonator, taking phase retardation into account. Through
this approach, we obtain a powerful Jones matrix formalism which can be used to
calculate the polarization rotation, ellipticity, and circular dichroism of
transmitted waves through stereometamaterials at any incident polarization. Our
experimental measurements agree well with our model.Comment: 10 pages, 3 figures, Theory and experimen
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