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

J. Sumaya-Martinez, J. Mulia-Rodriguez

TL;DR

We address the problem of achieving extraordinary acoustic transmission through a single subwavelength slit by engineering the slit’s boundary impedance. The authors introduce one or more narrow internal constrictions that act as impedance transformers, increasing the effective cavity length and transforming the entrance impedance toward the radiation impedance; this enables near-unity transmission without periodicity. A one-dimensional transmission-line model corroborated by numerical simulations reveals single-peak EAT with peak location tunable via ridge length $d$ and impedance contrast $Z_2/Z_1$, and multi-constriction configurations showing coupled-cavity resonance splitting. The findings underscore a universal impedance-based mechanism for extraordinary transmission, with potential applications in compact, ultra-thin acoustic filters and sensors that rely on impedance-matched interfaces rather than geometrical periodicity.

Abstract

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.

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

TL;DR

We address the problem of achieving extraordinary acoustic transmission through a single subwavelength slit by engineering the slit’s boundary impedance. The authors introduce one or more narrow internal constrictions that act as impedance transformers, increasing the effective cavity length and transforming the entrance impedance toward the radiation impedance; this enables near-unity transmission without periodicity. A one-dimensional transmission-line model corroborated by numerical simulations reveals single-peak EAT with peak location tunable via ridge length and impedance contrast , and multi-constriction configurations showing coupled-cavity resonance splitting. The findings underscore a universal impedance-based mechanism for extraordinary transmission, with potential applications in compact, ultra-thin acoustic filters and sensors that rely on impedance-matched interfaces rather than geometrical periodicity.

Abstract

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.
Paper Structure (11 sections, 7 equations, 3 figures)

This paper contains 11 sections, 7 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Theoretical model
  3. Uniform slit as a reference
  4. Single internal constriction
  5. Multiple constrictions
  6. Numerical results
  7. Single internal constriction: ridge length
  8. Single internal constriction: impedance contrast
  9. Two internal constrictions: separation and mode splitting
  10. Discussion
  11. Conclusions

Figures (3)

  • Figure 1: Power transmittance $T$ as a function of normalized wavelength $\lambda/h$ for a single subwavelength slit containing one internal constriction of length $d$. Curves correspond to several values of $d/h$ at fixed impedance contrast $Z_2/Z_1=4$. The uniform slit ($d=0$) exhibits weak transmission, while a finite constriction yields a strong extraordinary-transmission peak that redshifts as $d/h$ increases due to an effective increase of the acoustic cavity length.
  • Figure 2: Power transmittance $T$ as a function of normalized wavelength $\lambda/h$ for a single internal constriction of fixed length $d/h=0.4$, and different impedance contrasts $Z_2/Z_1$. Moderate contrasts yield sharp, high-transmission resonances, while very large contrasts reduce the peak transmission due to stronger reflection at the impedance discontinuities.
  • Figure 3: Power transmittance $T$ as a function of normalized wavelength $\lambda/h$ for a subwavelength slit containing two identical internal constrictions of length $d/h=0.2$ separated by a distance $s$. For $s=0$ the system behaves as a single longer constriction and supports one extraordinary-transmission peak. Increasing $s$ leads to resonance splitting, characteristic of coupled-cavity behavior.