  Recently, the domain of topological insulators in condensed matter physics
has been teeming with intriguing and very exciting discoveries. Notably, the
capacity of guiding currents towards specific directions according to the spin
of the travelling electrons has a great potential for electronic devices. This
new phenomenon has been transposed to the classical domain in electromagnetics
and acoustics, unveiling the pseudo-spin locking of guided waves. However,
these macroscopic analogues are photonic/phononic crystals which are
intrinsically wavelength scaled. In this work, we realize a genuine acoustic
analogue of the valley-Hall effect in the audible regime using a lattice of
soda cans. The crystalline description of this very simple metamaterial allows
us to demonstrate experimentally the unidirectional excitation of sound guided
at a scale much smaller than the wavelength of operation. These results not
only open the tantalizing valley-topological phenomena to the audible regime
but also allow to envision compact applications for acoustic manipulation.
