  Negative refraction of acoustic waves is demonstrated through underwater
experiments conducted at ultrasonic frequencies on a 3D locally resonant
acoustic metafluid made of soft porous silicone-rubber micro-beads suspended in
a yield-stress fluid. By measuring the refracted angle of the acoustic beam
transmitted through this metafluid shaped as a prism, we determine the acoustic
index to water according to Snell's law. These experimental data are then
compared with an excellent agreement to calculations performed in the framework
of Multiple Scattering Theory showing that the emergence of negative refraction
depends on the volume fraction $\Phi$ of the resonant micro-beads. For diluted
metafluid ($\Phi=3\%$), only positive refraction occurs whereas negative
refraction is demonstrated over a broad frequency band with concentrated
metafluid ($\Phi=17\%$).
