Ultrasonic wave transport in concentrated disordered resonant emulsions

We show how resonant (near-field) coupling affects wave transport in disordered media through ultrasonic experiments in concentrated suspensions. The samples consist of resonant emulsions in which oil droplets are suspended in a liquid gel. By varying the volume fraction of droplets φ up to 40%, the limits of the independent scattering approximation are experimentally demonstrated as soon as φ>10%. For these concentrated samples, the proximity of resonant scatterers induces a renormalization of the surrounding medium, leading to a reduction in scattering strength. Hence, maximum scattering is reached at an intermediate droplet concentration (20%<φ<30%) where subdiffusive wave transport is observed. These results are very relevant for designing materials for the study of wave transport phenomena such as Anderson localization. © 2023 American Physical Society.