Propagation of ultrasound in aqueous foams: bubble size dependence and resonance effects

• DOI: 10.1039/c2sm25545f
• Publication Date: 2012-11-26T16:17:39Z
• Authors: Imen Ben Salem; Reine-Marie Guill...; Caitlin Sample; Valentin Leroy; Arnaud Saint-Jalmes; Benjamin Dollet
• Keywords: Speed of Sound

We report experimental results on the propagation of ultrasonic waves (at frequencies in range 40 kHz) aqueous foams. Monitoring acoustics foams as they age, i.e. mean bubble radius increases by coarsening, we recover at short times some trends that are already known: decrease speed sound and increase attenuation. At long times, have identified, for first time, robust non-monotonic behaviors attenuation, associated with a critical size, which decreases increasing frequency. The features appear to be surprisingly reminiscent Minnaert resonance known single isolated fluid. Transposing theoretical framework limit dense packing bubbles gives qualitative agreement data, but still cannot explain quantitatively measured properties.