  A bubble meta-screen is an exceptionally effective and low frequency
resonator which can be optimized in order to exactly balance the energy
provided by radiative process and lost under a viscous mechanism (critical
coupling). Under this condition, one can absorb 99.9% of the energy carried by
two phase-matched counter propagating acoustic beams. This phenomenon, called
coherent perfect absorption, is here observed with bubbles 75 times smaller
than the incident wavelength and is shown to be remarkably broadband. Finally,
tuning the relative phases of the two beams turns out to be an efficient way to
control the absorption in the medium.
