Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perfect and broadband acoustic absorption by critical coupling   We experimentally and analytically report broadband and narrowband perfect
absorption in two different acoustic waveguide-resonator geometries by the
mechanism of critical coupling. In the first geometry the resonator (a
Helmholtz resonator) is side-loaded to the waveguide and it has a moderate
quality factor. In the second geometry the resonator (a viscoelastic porous
plate) is in-line loaded and it contains two resonant modes with low quality
factor. The interplay between the energy leakage of the resonant modes into the
waveguide and the inherent losses of the system reveals a perfect and a
broadband nearly perfect absorption. The results shown in this work can
motivate relevant research for the design of broadband perfect absorbers in
other domains of wave physics.

25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math