Speed Of Sound Research Articles

Tetrascatt Model: Born Approximation for the Estimation of Acoustic Dispersion of Fluid-Like Objects of Arbitrary Geometries

Abstract Modeling the acoustic scattering response due to penetrable objects of arbitrary shapes, such as those of many marine organisms, can be computationally intensive, often requiring high-performance computing equipment when considering a completely general situation. However, when the physical properties (sound speed and density) of the scatterer are similar to those of the surrounding medium, the Born approximation provides a computationally efficient way to calculate it. For simple geometrical shapes like spheres and spheroids, the acoustic scattering in the far field evaluated through the Born approximation recipe results in a formula that has been historically employed to predict the response of weakly scattering organisms, such as zooplankton. Further, the Born approximation has been extended to bodies whose geometry can be described as a collection of noncircular rings centered on a smooth curve. In this work, we have developed a numerical approach to calculate the far-field backscattering by arbitrary 3D objects under the Born approximation. The object's geometry is represented by a volumetric mesh composed of tetrahedrons, and the computation is efficiently performed through analytical 3D integration, yielding a solution expressed in terms of elementary functions. On a current desktop PC the model can compute the scattering from meshes with millions of elements in a matter of minutes. This model is able to compute the scattering from a complex shape 200× faster than other methods like the Boundary Element Method, without compromising the numeric quality of the solution. The method's correctness has been successfully validated against benchmark solutions. Additionally, we present acoustic scattering results for species with complex geometries. To enable other researchers to use and validate the method, a computational package named tetrascatt was developed in the R programming language and published in the CRAN (Comprehensive R Archive Network).

Charged Stellar Structures with Adler-Finch-Skea Geometry in Ricci-inverse Gravity

Abstract We obtain a class of charged, anisotropic, and spherically symmetric solution characterized by the function $f(\mathcal{R},\mathcal{A})=\mathcal{R}+\alpha \mathcal{A}$, where $\mathcal{R}$ is the Ricci scalar, $\mathcal{A}$ is anticurvature scalar, and $\alpha$ is the coupling constant. The model was developed by utilizing the Karmarkar condition to produce the radial metric coefficient and adopting the time metric coefficient as proposed by Adler. We formulated the model by assuming a specific type of charge distribution within the stellar interior. We elaborated boundary conditions to ensure the continuity of the spacetime, considering the exterior spacetime as Bardeen's solution. In addition, we analyzed several physical entities, including the energy density, pressure components, anisotropy in pressure, energy conditions, equation of state, surface redshift, compactness factor, adiabatic index, sound speed, and Tolman-Oppenheimer-Volkoff equilibrium condition. The aforementioned conditions were satisfied, indicating that the solutions derived in this study are within the physically acceptable range.

Acoustic Propagation and Transmission Loss Analysis in Shallow Water of Northern Arabian Sea

This study investigates acoustic propagation and transmission loss in shallow water at an unexplored site in the northern Arabian Sea near the Pakistan coastline using a normal mode theoretical framework. Sound propagation in shallow water with range-independent bathymetry was analyzed using a customized Kraken C program to compute eigenvalues and eigenfunctions. The sound speed profile and clay silt sediment samples of the northern Arabian Sea, which characterize the water column and ocean bottom, respectively, were determined. Coherent and incoherent transmission losses for frequencies ranging from 50 to 500 Hz were calculated across different ranges and depths. Results indicate significant intensity fluctuations with increasing range, leading to higher transmission loss. Low frequencies (50–225 Hz) exhibit more significant transmission loss, while higher frequencies (230–500 Hz) show reduced loss. Transmission loss is higher for receivers at 19 m depth compared to those at shallower depths (8 m and 12 m) because the receivers are positioned near the layer of bottom sediments. Factors such as source and receiver depth, sediment properties, bottom roughness, and sound frequency significantly influence transmission loss. The novel dataset for the region supports the assessment of sonar performance, underwater communication, navigation, and marine life exploration.

Properties of interacting quark star in light of Rastall gravity

Abstract This study explores the properties of quark stars (QS) formulated with an interacting quark matter equation of state (EoS) within the framework of Rastall gravity, a modified theory of gravity. We derive the mass-radius relationships and calculate the maximum gravitational masses and their corresponding radii, comparing these results under both Rastall gravity and general relativity. Our analysis incorporates recent observational data, including the GW190425 event, to constrain the model parameters ($\bar{\lambda}, \eta, B_{\rm eff}$). We also assess the stability of these quark stars by evaluating their static stability, adiabatic index, and sound velocity profiles, \textcolor{blue}{thus confirming their viability within the modified gravitational framework}.

Effect of interstitial nitrogen on physical and mechanical properties of Al0.5CoCrNi high-entropy alloys: a first-principles study

Abstract The N-doped high entropy alloys (HEAs) have recently garnered significant interest for their outstanding mechanical properties, making them valuable structural materials within the industry, aerospace, and biomedical science. In this work, the impact of interstitial N atom on various properties of Al0.5CoCrNi HEA is investigated through first-principle calculations. Specifically, the changes in lattice constant, formation energy, elastic modulus, density of states, Vickers hardness, Debye temperature, energy factor, and charge density caused by the presence of interstitial N atom are analyzed. The results show that the interstitial N atoms lead to a decrease of the sample stability due to an increasing formation energy of the N-doped HEA. As the interstitial N content increases, the elastic module decreases, and an apparent anisotropy appears in N-doped HEA. Moreover, Vickers hardness decreases, suggesting the change of the stiffness and deformation characteristics. Compared to the N-doped tetrahedrons, the N-doped octahedrons exhibit high ductility due to an increasing Poisson’s ratio, a decreasing G/B ratio, and an increasing Cauchy pressure. The significant decreasing Debye temperature and average sound velocity reduces the thermal stability. The change of the electronic structure suggests the possibility for customizing electronic and optical properties. Additionally, the low energy factors for screw and edge dislocations promote dislocation nucleation in N-doped HEA. Charge density analysis reveals strong bonding characteristics, potentially affecting the chemical stability and reactivity. This work provides a unique perspective on the N-doped mechanical mechanism, and offers important insights for the advancement of advanced N-doped HEA.

The Viscosity of Liquids in the Dual Model

In this paper, a reliable model of the viscosity in liquids in the dual model of liquids (DML) framework is developed. The analytical expression arrived at exhibits the correct T–dependence Arrhenius-like exponential decreasing trend, which is typical of Newtonian simple fluids. The model is supported by the successful comparison with both the experimental values of the viscosity of water, and with those related to the mechano-thermal effect in liquids under low-frequency shear, discovered a few years ago, for which the first-ever theoretical interpretation is given by the DML. Moreover, the approach is even supported by the results of numerical models recently developed, that have shown that dual liquid models, such as the DML, provides very good agreement with experimental data. The expression of viscosity contains terms belonging to both the subsystems constituting the liquid, and shows an explicit dependence upon the sound velocity and the collective vibratory degrees of freedom (DoF) excited at a given temperature. At the same time, the terms involved depend upon the Boltzmann and Planck constants. Finally, the physical model is coherent with the Onsager postulate of microscopic time reversibility as well as with time’s arrow for macroscopic dissipative mechanisms.

Sucrose phononic crystal-based sensor via acoustically induced transparency

Abstract Accurate detection of sucrose concentration is vital for assessing sugar content in fruits, vegetables, and nuts. This article introduces an innovative method for sensing various sucrose concentrations using an acoustically induced transparency system integrated by a solid mechanic phononic crystal framework. The detector architecture is based on a two-dimensional phononic crystal that employs poly methyl methacrylate as its foundational material, complemented by a regularly spaced array of circular tungsten pillars. The layout features a linear waveguide linked to two coupled ring resonators, with the upper resonator housing four columns filled with varying sucrose concentrations, thereby enabling resonance frequencies that are specifically tailored to each concentration. Simulation findings demonstrate a strong correlation between the shifts in transmission peak frequency and the associated sound velocities and material densities. The sensor’s functionality is further confirmed through coupled mode theory, representative an excellent alignment with the sensor’s presentation. Particularly, the sensor achieves an impressive average quality factor of 53515, an average sensitivity of 195 Hz, a figure of merit of 4.75, a signal-to-noise ratio of 1.25, a resolution of 40 Hz, and average insertion losses of 1.48 dB. These results underscore the acoustically induced transparency system’s potential for precise sucrose concentration sensing, offering remarkable sensitivity and accuracy for agricultural applications.

The Parameterization of the Sound Speed Profile in the Sea of Japan and Its Perturbation Caused by a Synoptic Eddy

This study presents the description of the parameterization of sound speed distribution in the Sea of Japan in the presence of a synoptic eddy. An analytical representation of the background sound speed profile (SSP) on its periphery is proposed. The perturbation of sound speed directly associated with the presence of an eddy is investigated. The proposed parameterization of the background SSP leads to a Sturm–Liouville problem for normal mode computation, which is equivalent to the eigenvalue problem for the Schrödinger equation with the Morse potential. This equivalence leads to simple analytical formulae for normal modes and their respective horizontal wavenumbers. It is shown that in the presence of an eddy causing moderate variations in sound speed, the standard perturbation theory for acoustic modes can be applied to describe the variability in horizontal wavenumbers across the area in which the eddy is localized. The proposed parameterization can be applied to the sound propagation modeling in the Sea of Japan.

Unreported large errors in a common method for sound source localization of marine mammals.

Confidence intervals of location of calling marine mammals, derived from time differences of arrival (TDOA) between receivers, depend on errors of TDOAs, receiver location, clocks, sound speeds, and location method. Simulations demonstrate Ishmael, a TDOA locator based on uncorrected least squares minimization (ULSM), yields errors with mean, standard deviation, and maximum of 0.1, 0.2, and 0.9 km, respectively, due to sensitivity to inputs and numerical implementation when applied to scenarios with minuscule errors; e.g., five clock-synchronized receivers residing on the vertices of a square with one in its center. This sensitivity can mask other causes of location error due to small uncertainties in receiver location and sound speed. Realistic uncertainties of sound speed up to ±7.5 m/s lead to errors up to 4 km. With unsynchronized clocks and common practice of correcting TDOA from synchronization measurements at the start and end of an experiment, errors of location are 10 to 1000 km. These problems occur because ULSM was not designed to account for all errors. ULSM is also available in PAMGuard and other systems and is used to study behavior and abundance of calling marine mammals. ULSM is briefly compared to another method designed to account for errors.

Effects of ellipsoidal shapes on sound velocity in particle systems: From spherical to elongated shapes

Effects of ellipsoidal shapes on sound velocity in particle systems: From spherical to elongated shapes

Physical viability of [formula omitted] gravity corrected charged anisotropic solutions

This article explores the impact of charge on the properties of relativistic compact star candidates exhibiting anisotropic distribution in f(Q) gravity, where Q represents a nonmetricity. A specific model of this gravitational theory is considered to simplify the system and establish the precise field equations that regulate the interaction between matter and geometry. Analysis of the static spherical symmetric structures is conducted by considering the non-singular feasible solutions. The Darmois constraints are used to determine the unknown constants in the metric coefficients. We explore different physical characteristics in the interior of charged compact stars to check their viability. Sound velocity and adiabatic index techniques are employed for stability state analysis. Proposed charged stars are determined to be both viable and stable in this theoretical framework.

Spherically symmetric perfect fluid filled universe within the 4 dimensional Einstein–Gauss–Bonnet gravity formalism with vanishing conformal curvature

Conformally flat spacetime geometry is of immense physical importance. In this conext we obtain the most general solutions for 4 dimensional Einstein-Gauss–Bonnet (4D EGB) static spherically symmetric spacetimes. The standard Schwarzschild incompressible fluid sphere is one possible solution, however, new branches of solutions emerge that have cosmological significance. It is intriguing that the geometry of the new model is given by an exactly known spatially directed potential while the remaining potential is given as an integral. It is not necessary to know the explicit form of the temporally directed potential to analyse the physics of the model. However, at least two explicit exact solutions for both potentials are exhibited. Graphical plots are constructed to show that barring a short interval from the centre of the distribution which may be excised and replaced with a well-behaved fluid, all the elementary physical tests are successful. The model considered does not admit a finite radius hence is not applicable to astrophysical compact objects however the pleasing physical characteristics of the fluid suggests applicability to a perfect fluid filled universe. The model satisfies the causality requirement preventing the sound speed from becoming superluminal as well as the Chandrasekar stability criterion demanded of adiabatic fluids. Moreover all the energy conditions are complied with. The analysis effectively rules out the existence of conformally flat stars in 4D EGB gravity aside from the interior Schwarzschild spacetime.

Sound velocity measurement of pipeline fluids based on wavenumber-frequency spectrum

Sound velocity measurement of pipeline fluids based on wavenumber-frequency spectrum

Global climatological dataset of undersea acoustic parameters derived from the NCEI World Ocean Atlas 2023

Acoustics is most effective in undersea detection, localization, and communication. Establishment of a global climatological dataset of undersea acoustic parameters becomes urgent. In building such a dataset, first we use the Thermodynamic Equation of Seawater-2010 (TEOS-10) to calculate the sound speed (SS) from the gridded temperature and salinity fields of the NOAA/NCEI World Ocean Atlas 2023. Second, we determine the depth of overall minimum from SS profile as the deep sound channel (DSC) axis depth, the depth of overall maximum between the surface and DSC axis as the sonic layer depth (SLD), the depth of the local minimum between SLD and DSC axis as the second sound channel (SSC) depth, and the depth with the SS equalling the maximum SS as the critical depth. Third, we obtain the SS at the surface, SLD, DSC axis, and SSC axis. Fourth, we determine the other acoustic parameters such as In-layer gradient, below layer gradient, DSC strength, SSC strength, depth excess, and surface duct cut-off frequency. The dataset is publicly available.

Exploring the viability of charged spheres admitting non-metricity and matter source

This research paper investigates the impact of non-metricity and matter source on the geometry of charged spheres in the presence of anisotropic matter configuration. We use a specific model of extended symmetric teleparallel theory to minimize the complexity of the field equations. Moreover, the feasible non-singular solutions are used to examine the interior composition of the charged spheres. The Darmois junction conditions are used to determine the unknown constants in the metric coefficients. We explore some significant properties in the interior of compact stars under consideration to check their viable existence in this modified framework. The equilibrium state of the charged spheres is discussed using the Tolman–Oppenheimer–Volkoff equation and stability is analyzed by sound speed and Herrera cracking approach. We find that the charged spheres in this theoretical framework are physically viable and stable.

Topological interface states in solid/liquid phononic crystal waveguides and sensing applications

Topologically protected states in phononic crystals provide a new avenue to design robust acoustic devices as they are immune to structural imperfections or defects. In this work, the topological characteristics of solid/liquid phononic waveguides are investigated numerically using the finite element approach. Both the topologically trivial and non-trivial phononic crystals can be obtained by varying their geometry and hence are used for the construction of the phononic crystal structure that possesses the topological interface state. Furthermore, the wave barriers are designed by using another kind of PCs with a complete band gap, which can reduce the negative effect of acousto-structural interaction at the waveguide boundaries. The topological interface state is employed for the detection of sound velocity of the mixtures of water and 1-propanol. Importantly, the sensing quantities of the topological phononic crystal sensor are robust against introduced structural perturbations.

Erosion enhancement by impurity entrainment in the highly collisional plasmas of Magnum-PSI

Abstract Extrinsic impurity seeding is planned for ITER to avoid high heat fluxes to the tungsten divertor targets. Nevertheless, excessive sputtering by impurities would lead to a reduction in fusion power output and divertor lifetime. Unlike today's fusion devices, the entrainment of impurities is expected to play an increasing role in ITER's highly collisional near-surface plasma. Impurity entrainment refers to the acceleration of impurities with the plasma flow by collisional drag, leading to elevated impact energies. To investigate impurity entrainment under ITER-like plasma conditions ($n_e > 2 \cdot 10^{20}$ m$^{-3}$, $T_e <$ 5 eV), argon-seeded hydrogen plasmas were formed with the linear plasma generator Magnum-PSI. Doppler shifts in spatially-resolved emission profiles of argon (Ar II - 480.6 nm) and hydrogen (H$_\mathrm{\beta}$ - 486.1 nm) reveal the entrainment of seeded argon towards the upstream hydrogen velocity ($\sim$9 cm from surface), corresponding to $\sim$0.39 of the common-system sound speed. In addition, the sputtering yield of tungsten by argon bombardment for the argon-seeded hydrogen plasma was compared to a pure argon plasma by monitoring tungsten (W I - 400.9 nm) emission. These sputtering experiments indicate further entrainment of the argon impurities to $\sim$0.65 of the common-system sound speed at the sheath edge, leading to a large increase in their impact energy. Extrapolation of the Magnum-PSI results to ITER, using existing SOLPS-ITER simulations to determine the divertor plasma conditions, indicates more than an order of magnitude increase in gross erosion of the divertor targets due to impurity entrainment. However, the net erosion rate could still be kept under control if high re-deposition rates are achieved, which is treated in the companion paper \cite{Cornelissen2023}. The combination of a low sputtering threshold energy and high impact energy of impurities constrains the fine balance between radiative cooling with impurity seeding and avoiding extensive divertor erosion.

Aging of Limestones and Silane–Siloxane-Based Protective Hydrophobics: The Impact of Heating–Cooling and Freeze–Thaw Cycles

Stones are traditionally used in construction and architectural applications as building elements due to their aesthetic and technical/structural performance. Like other environmental factors (rain, humidity, moisture, salt presence, biological activity, etc.), heating–cooling and freeze–thaw cycles significantly threaten the longevity of stone materials. Hence, considering the socio-economic and cultural value of stones, preventive measurements such as hydrophobic coatings are applied to prevent or mitigate damage. The scope of this study is the performance assessment of limestones with different characteristics and the efficiency of various commercial silane/siloxane-based hydrophobic coatings when exposed to thermal variation and freeze–thaw. For that purpose, the standards EN 14066:2013 (determination of resistance to aging by thermal shock) and EN 12371:2010 (determination of frost resistance) were followed. Open porosity and static contact angles were estimated to assess the stone durability and water protection capabilities of the hydrophobics. Additionally, sound speed propagation velocity, quality of building material index, elastic modulus and flexural strength were measured to evaluate the variation of mechanical properties. Static contact angle revealed that the coatings maintained an efficient level of hydrophobicity even after thermal-shock and freeze–thaw weathering tests. The study also revealed a critical interaction between freeze–thaw cycles, hydrophobic coatings and structural integrity of the stones, mostly on more porous ones. When they are subjected to harsh environmental conditions, untreated porous limestones keep structural cohesion, allowing for the natural absorption and release of water during freezing and thawing. On the contrary, when limestones are treated, the hydrophobic coatings can moderately obstruct the water release due to the partial saturation of the porous framework by the products. It also probably resulted from the different mechanical behavior between the inner matrix and layer of stone coated, resulting in a premature breakout and mechanical damage of the stone.

Enhancing Backscatter Data Processing Through Sound Speed and Salinity Proxies

Enhancing Backscatter Data Processing Through Sound Speed and Salinity Proxies

Performance of underwater data transmission using incoherent modulation MFSK in very shallow waters

Ensuring universal and stable underwater communication in shallow waters for various environmental conditions is a difficult scientific and engineering task. This applies in particular to underwater communication systems that use acoustic waves in very shallow underwater channels, where multipath propagation permanently occurs. The article provides assumptions for a system working with incoherent M-ary Frequency-Shift Keying (MFSK) modulation, along with guidelines for eliminating the impact of the multipath phenomenon. The results of experimental tests carried out in a lake for two seasons and, therefore, different sound velocity profiles are presented. For comparison purposes, three transducers placed at different depths, including at the bottom of the reservoir, were used to receive the transmitted signals.