Experimental Investigation of Acoustic Kerker Effect in Labyrinthine Resonators

Abstract

Controlling the directionality of the acoustic scattering with single acoustic metaatoms has a key importance for reaching spatial routing of sound with acoustic metamaterials. In this paper, we present the experimental demonstration of the acoustic analogue of the Kerker effect realized in a two-dimensional coiled-space metaatom. By engineering the interference between monopolar and dipolar resonances within a high-index acoustic metaatom, we achieve directional scattering with suppressed backward or forward response at the first and second Kerker conditions respectively. Experimental measurements of the scattered pressure field, in a parallel-plate waveguide environment, show good agreement with the full-wave simulations. Our results validate the feasibility of Kerker-inspired wave control in acoustic systems and open new opportunities for directional sound manipulation.

Figures (4)

• Figure 1: (a) Cylindrical function expansion of the field scattered by labyrinthine metaatom with geometry parameters $R=2.5$ cm, $r=0.9$ cm, $a=4$ mm, 8 sectors, and a curling number of 3. The points where first and second Kerker conditions are satisfied are marked with $K_1$ and $K_2$ respectively. (b) Monopole and (c) Dipole modes in a high-index labyrinthine metaatom. (d) Radiation patterns at Kerker and anti-Kerker conditions.
• Figure 2: (a) Schematic of the experimental setup for two-dimensional acoustic scattering measurements. The system comprises a parallel-plate waveguide constructed from two thin plexiglass sheets, with the edges terminated by wedges of sound-absorbing rubber foam to suppress boundary reflections. The overall dimensions of the setup are $1.5 \times 1.5 \times 0.066$ m, and the radiation patterns are recorded at a radial distance of $15$ cm. The signal is a chirped sweep of all covered frequencies. The signals are synchronized using loopback, and recorded using the sound card for further processing. (b) Amplitude and phase of the scattered at forwards and backwards points of the metaatom
• Figure 3: (a) Directivity, defined as the ratio between forward and backward scattering intensities, obtained from simulation and experiment; (b,c) simulated and measured radiation patterns at the frequencies corresponding to the first and second Kerker conditions, i.e., maximum forward and backward scattering, respectively. The metaatom used in simulation and experiment has following geometrical parameters: $R=4$ cm, $r=1$ cm, $a=6.2$ mm, 5 sections, 3 bendings of channel.
• Figure 4: (a) The dependence of resonance frequency of monopole and dipole modes on the channel width of the metaatom. Monopole (b) and dipole (c) mode intrincic, $Q_{\mathrm{rad}}$, radiative, $Q_{\mathrm{diss}}$ and total, $Q_{\mathrm{tot}}$, loss quality factor dependence on the channel width of the metaatom.