  We present the realization of an acoustic diode or rectifier, exploiting
symmetry-breaking nonlinear effects like harmonic generation and wave mixing
and the filtering capabilities of metamaterials. The essential difference and
advantage compared with previous acoustic diode realizations is that the
present is simultaneously a time invariant, frequency preserving and switchable
device. This allows its application also as an on-off or amplitude-tuning
switch. We evaluate its properties by means of a numerical study and
demonstrate its feasibility in a preliminary experimental realization. This
work may provide new opportunities for the practical realization of structural
components with one-way wave propagation properties.
