Achieving Extraordinary Acoustic Transmission in a Single Slit by Boundary Impedance Engineering

Extraordinary acoustic transmission is commonly associated with periodic or multi-aperture structures. In this work, we show that a single subwavelength slit can support strongly enhanced transmission when its boundary response is described by an effective impedance. Using a reduced analytical model together with numerical calculations, we demonstrate that appropriate impedance tuning leads to efficient coupling between the incident field and the slit mode, resulting in transmission levels approaching unity. The observed enhancement is governed by impedance matching rather than geometric periodicity, highlighting a minimal mechanism for extraordinary transmission. This study establishes boundary impedance control as a versatile route for manipulating acoustic wave transport through deeply subwavelength apertures.