# Longitudinal near-field coupling between acoustic resonators grafted onto a waveguide

## TL;DR

This study explores how acoustic resonators attached to a waveguide interact through near-field coupling, revealing effects like Fano profiles and Fabry-Perot interferometers, supported by experiments and finite element analysis.

## Contribution

It demonstrates the influence of longitudinal near-field coupling on acoustic transmission and introduces the formation of resonant interferometers in a simple resonator array.

## Key findings

- Near-field coupling affects transmission around resonances.
- Fano-like profiles emerge in far-field arrangements.
- Resonant interferometers explain observed transmission features.

## Abstract

We investigate longitudinal near-field coupling between acoustic resonators grafted onto a waveguide. Experiments are performed in the audible range with a simple acoustic system composed of a finite aperiodic sequence of air resonators. Transmission typically shows a zero around a resonance frequency of a single resonator, as is well known. When two identical resonators are brought in close proximity, however, we observe that longitudinal near-field coupling strongly influences the acoustic transmission. When the separation between resonators is increased so that they can be considered in the far field of one another, we further observe the appearance of Fano-like transmission profiles. We explain this observation by the formation of locally resonant Fabry-Perot interferometers from every pair of resonators. All experimental results are compared to three-dimensional finite element analysis of the acoustic system.