Broadband ventilated meta-barrier based on the synergy of mode superposition and consecutive Fano resonances

Sound insulation under ventilation conditions is an important issue in acoustic fields that has significant applications in various practical scenarios. The emergence of acoustic metasurfaces breaks the limitation of manipulating large-scale waves at subwavelength scales and enables a better ventilating capability, while there is still a problem that the bandwidth of previous studies is usually smaller than half an octave. Here, we design and experimentally implement a ventilated meta-barrier with subwavelength thickness capable of realizing broadband sound insulation while maintaining efficient ventilation. The underlying mechanism is the synergy of the consecutive Fano resonances and superposition of equal-strength monopolar mode of the gradient helical structure and dipolar mode of the central orifice, leading to an efficient blocking of approximately 90% of sound waves coming from various directions in the range from 1145 to 1815 Hz while preserving high-efficiency ventilation. The experiments are conducted to verify the effectiveness of the resulting device, which is in good agreement with the simulated results and theoretical predictions. Our design with functionality and flexibility opens up possibilities for the design of broadband ventilated acoustic devices and may find important application prospects in diverse fields such as noise control and architectural acoustics.