Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Acoustic metamaterial absorbers based on confined sonic crystals   Theoretical, numerical and experimental results examining thermoviscous
losses in sonic crystals are presented in this work, enabling the fabrication
and characterization of an acoustic metamaterial absorber with complex-valued
anisotropic inertia. The formulations developed can be written with no unknown
or empirical coefficients, due to the structured lattice of the sonic crystals
and organized layering scheme, and it is shown that higher filling fraction
arrangements can be used to provide a large enhancement in the loss factor. To
accurately describe these structures in a realizable experimental
configuration, confining structures are needed which modify the effective
properties, due to the thermal and viscous boundary layer effects within the
sonic crystal lattice. Theoretical formulations are presented which describe
the effects of these confined sonic crystals, both individually and as part of
an acoustic metamaterial structure, and is demonstrated experimentally in an
acoustic impedance tube. It is observed that confined sonic crystals
demonstrate an increase in the viscous losses and a reduction in the effective
bulk modulus, enabling better acoustic absorber performance through improved
impedance matching and enhanced absorption.

7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
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The categories of this paper are: nlin
30
The categories of this paper are: q-alg