Frequency-tunable sound insulation via a reconfigurable and ventilated acoustic metamaterial

Abstract

In acoustic engineering, sound-proofing ventilation barriers find wide applications in diverse situations. However, most of the structures only have responses with fixed frequencies and a very narrow frequency range, especially for low frequency acoustics. Here we show a subwavelength acoustic metamaterial based on labyrinthine structures, which possesses tunable sound insulation and ventilation properties. The Fano-like asymmetric transmission dips is formed by the interference between the resonant scattering of discrete states and the background scattering of continuous states. By adjusting the spacing between these two half zigzag molds, the sound insulation dip frequency can shift from 360 Hz to 575 Hz while the free ventilation area ratio is kept to over 36.3% and the total thickness is only about 0.06λ. Moreover, the noise peak frequency can be detected by a microphone detection and adaptive adjustment of the spacing with a small stepping motor is demonstrated, the results agree well with numerical simulations. We anticipate our design may find potential applications in acoustic air vents, soundproofing window and duct noise control.