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In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorouscoupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths. [ABSTRACT FROM AUTHOR]

In this letter, we have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing, and acoustic devices. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate that acoustic waves can achieve extremely flat transmission through a metallic grating under oblique incidence within multiple frequency bands separated by Wood's anomalies. At the low-frequency band, the transmission of acoustic wave is independent of the frequency and presents a flat curve with the transmission efficiency reaching about 100%; while at high-frequency bands, the transmission decreases to be lower flat curves due to the diffraction effect. The transmission efficiency is insensitive to the thickness of the grating. This phenomenon is verified by experiments, numerical simulations, and an analytical model. The broadband high transmission is attributed to the acoustic impedance matching between the air and the grating. This research may open up a field for various potential applications of acoustic gratings, including broadband sonic imaging and screening, grating interferometry, and antireflection cloaking. [ABSTRACT FROM AUTHOR]