  We experimentally achieve selective wave filtering and polarization control
in a three-dimensional elastic frame embedding local resonators. By connecting
multi-resonating elements to a frame structure, a complete low-frequency,
subwavelength bandgap with strong selective filtering properties is obtained.
Theory and experiments demonstrate the metaframe capability to selectively stop
transverse waves while allowing longitudinal wave propagation, as in
'fluid-like' elasticity. This peculiar behaviour, together with the complete
bandgap structure, may open opportunities in the context of wave control,
envisaging concurrent applications for three-dimensional filters and elastic
wave polarizers.
