Broadband compact acoustic absorber with high-efficiency ventilation performance

The trade-off between the low-frequency sound absorption and ventilation efficiency in conventional acoustic absorbers limits their application potentials in many scenarios. Here, we design and experimentally implement a broadband compact acoustic absorber for absorbing low-frequency airborne sound, and the absorption coefficient above 0.5 ranges from 850 to 1000 Hz. We analytically analyze our proposed mechanism that uses double-layered perforated metastructure on each side to simultaneously lower the working frequency and ensures a high ventilation efficiency (with 70% cross-section open), which are verified both numerically and experimentally. Our work opens up possibilities for the design of acoustic absorbers working at a low frequency and may find practical applications such as noise control in small ventilating spaces.