  We study the energy flux carried by acoustic waves excited by convective
motions at sub-photospheric levels. The analysis of high-resolution
spectropolarimetric data taken with IMaX/Sunrise provides a total energy flux
of ~ 6400--7700 Wm$^{-2}$ at a height of ~ 250 km in the 5.2-10 mHz range, i.e.
at least twice the largest energy flux found in previous works. Our estimate
lies within a factor of 2 of the energy flux needed to balance radiative losses
from the chromosphere according to Anderson & Athay (1989) and revives interest
in acoustic waves for transporting energy to the chromosphere. The acoustic
flux is mainly found in the intergranular lanes but also in small
rapidly-evolving granules and at the bright borders, forming dark dots and
lanes of splitting granules.
