  Ventilation barriers allowing simultaneous sound blocking and free airflow
passage are of great challenge but necessary for particular scenarios calling
for sound-proofing ventilation. Previous works based on local resonance or
Fano-like interference serve a narrow working range around the resonant or
destructive-interference frequency. Efforts made on broadband designs show a
limited bandwidth typically smaller than half an octave. Here, we theoretically
design an ultra-broadband ventilation barrier via hybridizing dissipation and
interference. Confirmed by experiments, the synergistic effect from our
hybrid-functional metasurface significantly expand the scope of its working
frequencies, leading to an effective blocking of more than 90% of incident
energy in the range of 650-2000 Hz, while its structural thickness is only 53
mm $(\sim \lambda / 10)$. Our design shows great flexibility in customizing the
broadband and is capable of handling sound coming from various directions,
which has potential in air-permeable yet sound-proofing applications.
