  As an important problem in acoustics, sound insulation finds applications in
a great variety of situations. In the existing schemes, however, there has
always been a tradeoff between the thinness of sound-insulating devices and
their ventilating capabilities, limiting their potentials in the control of
low-frequency sound in high ventilation environments. Here we design and
experimentally implement an omnidirectional acoustic barrier with planar
profile, subwavelength thickness (0.18lambda) yet high ventilation. The
proposed mechanism is based on the interference between the resonant scattering
of discrete states and the background scattering of continuous states that
induces Fano-like asymmetric transmission profile. Benefitting from the
binarystructured design of coiled unit and hollow pipe, it maximally simplifies
the design and fabrication while ensuring the ventilation for all the non
resonant units with open tubes. The simulated and measured results agree well,
showing the effectiveness of our proposed mechanism to block low frequency
sound coming from various directions while allowing 63% of the air flow to
pass. We anticipate our design to open routes to design sound insulators and to
enable applications in traditionally unattainable cases such as those calling
for noise reduction and cooling simultaneously.
