Rapid tablet swelling and disintegration during exposure to brightness-mode ultrasound

Controlled tablet disintegration is useful for chemical consistency checks. This study monitored the swelling of 54 analgesia tablets from two different batches, during 13–6-MHz brightness-mode sonication and simultaneous video recording. The tablets were placed on an acoustic reflector inside a container and sonicated from the top. Sonication shortened the displacement half-life by 17%–27%. During tablet swelling, their speed of sound increased linearly, confirming the linearity of the this process. Diagnostic ultrasound significantly decreased tablet disintegration times, supporting the ultrasound–microbubble interaction hypothesis.

Noninvasive estimation of local speed of sound by pulse-echo ultrasound in a rat model of nonalcoholic fatty liver

Objective: Speed of sound has previously been demonstrated to correlate with fat concentration in the liver. However, estimating speed of sound in the liver noninvasively can be biased by the speed of sound of the tissue layers overlying the liver. Here, we demonstrate a noninvasive local speed of sound estimator, which is based on a layered media assumption, that can accurately capture the speed of sound in the liver. We validate the estimator using an obese Zucker rat model of non-alcoholic fatty liver disease and correlate the local speed of sound with liver steatosis. Approach: We estimated the local and global average speed of sound noninvasively in 4 lean Zucker rats fed a normal diet and 16 obese Zucker rats fed a high fat diet for up to 8 weeks. The ground truth speed of sound and fat concentration were measured from the excised liver using established techniques. Main Results: The noninvasive, local speed of sound estimates of the livers were similar in value to their corresponding "ground truth'' measurements, having a slope ± standard error of the regression of 0.82 ± 0.15 (R2 = 0.74 and p < 0.001). Measurement of the noninvasive global average speed of sound did not reliably capture the ``ground truth'' speed of sound in the liver, having a slope of 0.35 ± 0.07 (R2 = 0.74 and p < 0.001). Decreasing local speed of sound was observed with increasing hepatic fat accumulation (approximately -1.7 m/s per 1% increase in hepatic fat) and histopathology steatosis grading (approximately -10 to -13 m/s per unit increase in steatosis grade). Local speed of sound estimates were highly correlated with steatosis grade, having Pearson and Spearman correlation coefficients both ranging from -0.87 to -0.78. In addition, a lobe-dependent speed of sound in the liver was observed by the ex vivo measurements, with speed of sound differences of up to 25 m/s (p < 0.003) observed between lobes in the liver of the same animal. Significance: The findings of this study suggest that local speed of sound estimation has the potential to be used to predict or assist in the measurement of hepatic fat concentration and that the global average speed of sound should be avoided in hepatic fat estimation due to significant bias in the speed of sound estimate.

First Sounds from Mars

Perseverance’s microphones provide the first characterization of Mars’ acoustic environment and pressure fluctuations in the audible range and beyond, from 20 Hz to 50 kHz. Prior to this mission, modeling predicted that: (i) atmospheric turbulence must change at centimeter scales or smaller at the point where molecular viscosity converts kinetic energy into heat, (ii) the speed of sound varies at the surface with frequency, and (iii) high frequency acoustic waves are strongly attenuated with distance in CO2. However, theoretical models were uncertain because of a lack of experimental data at low pressure, and the difficulty to characterize turbulence or attenuation in a closed environment. Here we present in situ recordings for the first 216 solar days of the Mars 2020 mission. We find that atmospheric sounds extend measurements of the dynamic pressure variations down to 1000 times smaller scales than ever observed before, revealing a dissipative regime of the Martian atmosphere extending over 5 orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), we highlight two distinct values for the speed of sound in the audible range that are ~10 m/s apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. We also provide the acoustic attenuation with distance above 2 kHz, allowing us to elucidate the large contribution of the CO2 vibrational relaxation in the audible range. These results establish a ground truth for modelling of acoustic processes, which is critical for small-scale atmospheric studies in atmospheres like Mars and Venus ones.

Acoustic Method of Quality Control of Two-Component Composite Materials

The features of using the acoustic method for accurately determining the concentration of components in two-component composite materials by measuring the speed of sound of long waves are described in this paper. Furthermore, explicit expressions for the volume concentrations of the matrix material and reinforcing particles or fibers of composite materials obtained by acoustic measurements are found. In addition, the advantages, features, and limits of the application of acoustic quality control of composite materials of various compositions and purposes are described. It is established that the methods for determining the concentration of components are valid for all types of composite materials, which are conveniently considered as phonon crystals. These results make it possible to more accurately determine or select a measuring cell for the experimental determination of the speed of sound. The mathematical problem to be solved is a purely exact inverse problem.

Average Intensity of Low-Frequency Sound and Its Fluctuations in a Shallow Sea with a Range-Dependent Random Impedance of the Liquid Bottom

In this study, the problem of the influence of a horizontally inhomogeneous liquid bottom impedance, given by random Gaussian function of the speed of sound and by density, on the propagation of low-frequency sound in a shallow-water waveguide is considered. The model parameters are referenced to the conditions of sound propagation in the regions of the seas of the Russian Arctic shelf. By the example of statistical modeling of the sound field intensity, we show that sound speed fluctuations in the bottom lead to similar effects that were previously established for volumetric fluctuations of the speed of sound in the water layer. With the distance from the source, the decrease in the average intensity slows down in comparison with a deterministic medium in which there are no fluctuations. This deceleration of the decay of the intensity in a random waveguide can be significant already at short distances. Changes in the law of decay of intensity at a fixed frequency are mainly determined by the correlation radius of inhomogeneities and the average penetrability of the bottom, which leads to attenuation of sound propagating in the waveguide.