Extraordinary acoustic transmission (EAT) through cascaded both-sides-open disk resonators (BSODRs) in a square lattice array (SLA) is investigated. A single BSODR consists of one disk cavity that is sandwiched by two tubes. These structures are realized by stacking perforated steel plates and immersing them in water. EAT is studied through single-layer, two-layer, three-layer, and four-layer BSODRs in SLAs. The EAT orders increase with increasing numbers of cascading layers. The quality factors of the highest order EAT peaks also increase with increasing numbers of cascading layers. The EAT characteristics of each structure can be predicted using a spring–mass model. A coupled spring–mass model with two oscillators is proposed. The vibration of the steel part is considered one oscillator and that of the water part of the BSODR represents the other oscillator. The model verifies that the EAT resonances are excited by coupling of the vibration from the steel plates to the water part. The experimental transmission spectra agree with the numerically simulated spectra. The EAT frequency is sensitive to the longitudinal sound velocity. Because of the increased quality factor, the figure of merit is enhanced eight times by cascading four BSODR layers. The proposed structure is suitable for acoustic filter and sensor applications.

Extraordinary acoustic transmission (EAT) is investigated numerically and experimentally using a square lattice array (SLA) of both-sides-open disk resonators (BSODRs) in a steel slab immersed in water. Each BSODR comprises a disk resonator sandwiched by two tubes and is formed by sticking three steel plates together, where each plate is perforated with a SLA of holes. The lattice constants of the three plates are the same, but the diameters of the holes in the middle plate are larger than those in the top and bottom plates. The BSODR resonance results in low-frequency EAT, and it is shown that the BSODR’s resonant behavior can be predicted using a spring–mass model. The EAT frequency can be reduced significantly by adjusting the diameters of the disk resonator and the tubes without changing their thicknesses. Oblique-incidence transmission shows that the low-frequency EAT is insensitive to the angle of incidence, and vibration of the top and bottom steel plates produces strong Fano-like line shapes in the EAT. Additionally, diffraction of the incident wave causes the steel plates to vibrate, and this excites two minor transmission peaks that correspond to Wood’s anomalies. As the disk resonator diameter increases, several eigenmodes that are dominated by the vibrations of the steel plates appear and lead to additional high-frequency EAT peaks; this behavior may suit applications that require robustness against variations in the ambient material properties. This structure provides increased flexibility for control of the EAT effect and can be applied in acoustic filters and sensors.