A bubble metascreen, i.e., a single layer of gas inclusions in soft solid, can be modeled as an acoustic open resonator, whose behavior is well captured by simple analytical expression. We show that tuning the parameters superabsorption achieved over broad frequency range, which confirmed finite element simulations and experiments. Bubble metascreens thus used ultrathin coatings for turning reflectors into perfect absorbers.Received 6 October 2014Revised 3 December...

We report the practical realization of phononic crystals with gas inclusions, using soft lithography techniques. Ultrasonic experiments from 0.3 to 5 MHz confirm existence deep and wide minima transmission through crystal. show that first gap is due combined effects Bragg reflections bubble resonances. propose a simple layered model gives reasonable prediction ultrasonic transmission.

Measurements of the phase velocity and attenuation sound in concentrated samples bubbly gels are presented. Hair gel was used as a matrix material to obtain well characterized distributions bubbles. Ultrasonic measurements were conducted over large range frequencies, including resonance frequencies Surprisingly good agreement with Foldy’s prediction found, even for monodisperse at up volume fraction 1%. Beyond this concentration, effects high-order multiple scattering observed. These results...

We measured the dispersion relation for acoustic longitudinal waves in liquid foams, over a broad frequency range (60--600 kHz). Strong was found, with two nondispersive behaviors, separated by negative density regime. A new model, based on coupled displacements of films, channels, and gas foam, rationalizes all experimental findings.

We present a class of sonic meta-screens for manipulating air-borne acoustic waves at ultrasonic or audible frequencies. Our screens consist periodic arrangements air bubbles in water possibly embedded soft elastic matrix. They can be used soundproofing, but also exalting transmission an air/water interface even to achieve enhanced absorption.

We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of standard stuff, we begin with detailed discussion radial movements air in water. This is managed from acoustic point view, and using Lagrangian rather than Eulerian variables. In unbounded water, air–water system has continuum eigenmodes, some them correspond regular Fabry–Pérot resonances. A singular resonance, lowest one, shown coincide that Minnaert. bounded...

Thanks to a multiple-scattering theory algorithm, we present way focus energy at the deep subwavelength scale, from far field, inside cubic disordered bubble cloud by using broadband time reversal (TR). We show that analytical calculation of an effective wavenumber performing independant scattering approximation (ISA) matches numerical results for focal extension. Subwavelength focusings $\ensuremath{\lambda}/100$ are reported simulations with perfect bubbles (no loss). A more realistic...

Nanobubbles are expected to dissolve in milliseconds. Experimental evidence of nanobubbles that were stable for days had thus been first received with circumspection. If the large number experimental confirmations has now made clear surface could exist, bulk still subject debate. When observations reported, main problem is make sure observed particles really gas. We show ultrasound an ideal tool investigating existence nanobubbles: 1) it sensitive minute quantities gas, 2) allows one...

We present experimental results on a model system for studying wave propagation in complex medium exhibiting low-frequency resonances. These experiments enable us to investigate fundamental question that is relevant many materials, such as metamaterials, where scattering resonances strongly influence the effective properties. This concerns effect of correlations positions scatterers coupling between their resonances, and hence transport through medium. To examine this experimentally, we...

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...

We measured the acoustic absorption, in 0.5–6 kHz frequency range, of polyurethane foams with mean pore diameters between 0.6 and 3.2 mm. Two types were investigated: classical open-cell ones versus membrane foams, which thin membranes preserved during solidification. Interestingly, latter presented better absorption abilities, indicating that could be an asset for sound absorption.

We investigate the interaction between Bragg and hybridization effects on band gap properties of bubble phononic crystals. These latter consist air cavities periodically arranged in an elastomer matrix are fabricated using soft-lithography techniques. Their transmission affected by due to periodicity structure as well propagating mode embedding medium resonance. The survives disorder while requires a periodic distribution bubbles. distance two layers can be tuned make gaps overlap or create peak gap.

Ultrasonic spectroscopy is used to characterize a model aerated food system consisting of agar gel in which both bubbles and polystyrene beads are embedded. By exploiting the distinct frequency dependence each inclusion's acoustic resonances, it demonstrated that sizes can be measured by ultrasound even when size distributions so similar these inclusions difficult distinguish optical images. While results demonstrate potential for applying ultrasonic evaluate any soft heterogeneous material...

Using a Multiple Scattering Theory algorithm, we investigate numerically the transmission of ultrasonic waves through disordered locally resonant metamaterial containing only monopolar resonators. By comparing cases perfectly random medium with its pair correlated counterpart, show that introduction short range correlation can substantially impact effective parameters sample. We report, notably, opening an acoustic transparency window in region hybridization band gap. Interestingly, is found...

A model for acoustic transmission through a 2D square crystal of R-radius bubbles with lattice constant L was previously proposed. Assuming purely monopole response the bubbles, this offers simple analytical expression transmission. However, it is not applicable when are too close to each other (L/R < 5). This article proposes an extension by including dipole bubbles. Comparisons numerical and experimental results show that new gives good estimate concentration at which no longer valid,...

We present a theoretical and experimental study of the acoustic second-harmonic generation by single layer bubbles. This simple system allows us to investigate subtle interplay between nonlinear effects multiple scattering. A perturbative model is shown give an excellent agreement with measurements, we demonstrate existence optimal concentration bubbles, for which harmonic maximum. The potential bubble screens as efficient subwavelength sources discussed.

We show that ultrasound can provide time‐resolved measurements of the size distribution and concentration bubbles in a liquid. The potential technique is demonstrated by following disappearance having an average radius 20 μm with 10 ms time resolution. our detect small concentrations bubbles, large spectrum accessible bubble radii (from 80 nm to 40 for gas volume fraction ), sub‐millisecond This new could be valuable tool investigating rapid processes such as nucleation or dissolution...

We discuss a series of easily reproducible experiments with one and two air bubbles immersed in water, we show that these systems can be analyzed terms harmonic oscillators.