  We present an experimental demonstration of sound absorption tailorability,
using acoustic metamaterials made of resonant cavities that does not rely on
any dissipative material. As confirmed by numerical calculation, we
particularly show that using quarter-wave-like resonators made of deep
subwavelength slits allows a high confinement of the acoustic energy of an
incident wave. This leads to enhance the dissipation in the cavities and,
consequently, generates strong sound absorption, even over a wide frequency
band. We finally demonstrate experimentally the key role of the filling ratio
in tailoring such an absorption, using a metamaterial constituted of
space-coiled cavities embedded in a polystyrene matrix. This paves the way for
tremendous opportunities in soundproofing because of its low density, low
volume, broadband and tailorable capabilities.
