Acoustic Pressure Distribution Research Articles

Noise generation and contribution of a single-gap bridge expansion joint: An experimental and numerical study

Noise generated from bridge expansion joints during vehicle passing has caused localized environmental problems around the world. The purpose of this paper is to investigate the vibration and noise radiation from the single-gap expansion joint induced by passing vehicles. First, a vibration and noise field test was performed for single-gap expansion joints in the highway ramps. Based on the tested results, two numerical models, involving a 3D tire-bridge expansion joint hybrid finite element model for the vibration analysis, as well as an acoustic boundary element model for the prediction of the noise radiation, were established and validated. The results of the numerical simulations and the field tests are well matched, which offers opportunities to predict the vibration and noise induced by vehicles passing through using the proposed methodology. Finally, the acoustic contribution and sound pressure distribution of different sound sources were discussed. The research showed that, for the single-gap expansion joint, the contribution of tire noise to the total noise level is dominant, and the contribution of structure-borne noise of the expansion joint and girder to the total noise level is insignificant. The findings emphasize the importance of tire noise and provide new ideas for noise control of single-gap expansion joints.

Centrifugal pump impeller wheel inspired acoustic metamaterial for low frequency sound absorption

Addressing low-frequency noise is a significant concern within the realm of acoustics and noise management. Labyrinthine channel based acoustic metamaterials have been proved to control low frequency noise using local resonance effect and thermoviscous dissipations. Drawing inspiration from centrifugal pump impeller wheel, an acoustic metamaterial absorber has been devised. The design incorporates impeller vanes to create a channel with variable widths and a micro-perforate panel through which sound wave propagates to the channels. Numerical simulations using COMSOL Multiphysics and experimental analysis are conducted employing Two microphone impedance tube method. Acoustic pressure and acoustic particle velocity distribution plots from numerical simulation study are used to comprehend the sound absorption mechanism. Sound absorption coefficient results reveal that this design offers a tunable sound absorption peak in low frequency regime. Furthermore, this paper discusses the influence of various geometric parameters such as, number of vanes, panel thickness and micro-hole diameter. The subwavelength dimensions of the design contribute to noise control in machineries with space constraints.

Experimental comparison of the effects of the two designed probes for exfoliation of graphene by sonication.

In the present research, comparative simulation and experimental investigation were carried out for two different probes to improve the efficiency and quality of few-layer graphene utilizing liquid-phase exfoliation. Two differently designed shaped probes are fabricated for this study, i.e., a simple probe and a stepped probe. The acoustic pressure distribution in the vessel is simulated for both probes at different output powers. In the experiment, both probes exfoliate graphite powder in a mixture of deionized water and ethanol. Different sonication times and output power were studied for different pulse modes. The graphene layers were characterized using Ultraviolet-visible spectroscopy (UV‒Vis), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Raman Microscope. The simulation shows that the total displacement on the tip of the stepped probe is 5.7% greater than that of the simple probe. Also, the pressure difference produced by the stepped probe is 9.15 × 106 pa compared to the pressure difference of the simple probe which is 8.23 × 106 pa. Consequently, the stepped probe was more effective in exfoliating graphene. The experimental results show that the absorbance peak in the stepped probe is approximately 32% greater than the absorbance peak in the simple probe with the same output power. Also, the graphene with better quality is produced with the stepped probe compared to the simple probe, which verifies the simulation findings. Additionally, the optimum output power, pulse duration, and sonication time to produce graphene with less time and energy consumption are obtained. The best graphene flakes were obtained via sonication with a pulse duration of 0.7 s, an output power of 282 W, and a sonication time of 45 min using a stepped probe. UV-Vis., SEM and TEM analysis show increases in quantity and quality of the exfoliated flakes. These results are approved by the peak ratio of I2D/IG around 1 in Raman spectra revealed the production of the few-layer graphene by the simple probe and the bilayer graphene by the stepped probe. So, this method is suitable for the production of graphene flakes from graphite in suitable quantity and quality.

Acoustic resonant metasurfaces with roughened necks for effective low-frequency sound absorption

The rise in environmental low-frequency noise from human-induced activities due to global urbanization has had a noticeable effect on the health and life quality of urban residents. Despite the implementation of conventional noise mitigation methods, they are only effective within a narrowband frequency range and their efficiency deteriorates when dealing with low-frequency noise. To address the existing problem in noise attenuation, an acoustic resonant metasurface that incorporates sliced Helmholtz-resonator-like substructures with embedded roughened necks is designed to achieve low-frequency sound absorption within a subwavelength scale. The theoretical model of this metasurface is first established, and then parametric studies are conducted to analyze the impact of various geometrical parameters on the sound absorption effect of the proposed metasurface. Subsequently, the sound absorption performance of the proposed design is investigated through numerical and experimental studies using two samples at both single and broadband frequencies. Excellent absorption performances by the samples at a low-frequency spectrum have been achieved. To understand the underlying absorptive mechanism of the proposed metasurface models, theoretical investigations are conducted for acoustic impedance and complex frequency, while numerical studies are also carried out to examine the distribution of acoustic pressure, acoustic velocity and thermoviscous power dissipation density. The research findings presented in this study may facilitate the development of an effective acoustic barrier for low-frequency noise (≤ 200 Hz).

An application and discussion of wide-band signal processing technology in the primary calibration for hydrophones

Abstract Wide-band signals are potentially available in the measurement of transducers, which can obtain wide-band responses of electroacoustic parameters of them directly. The hydrophone of B&K 8103 is calibrated in a Φ 1.2 m×1.8 m small water vessel by wide-band signal processing technology in the frequency range of 3.15 kHz to 100 kHz. A thin pellicle co-vibrates with acoustic particle in the free-field, and its oscillation can be detected by a laser Doppler vibrometer, which can estimate the acoustic pressure distribution. The transfer function model is established in a small water vessel, and the wide-band frequency responses of the transfer impedance of transducer and hydrophone as well as the transfer impedance of transducer and pellicle in the small water vessel are calculated respectively. The wide-band signal processing technology of frequency domain filter process are used, which can isolate the reflecting acoustic wave from the boundaries and the surface of the water vessel. To verify the accuracy of the wide-band calibration measurements, the calibration results are compared with that using tone-burst signals in the water vessel and using free-field reciprocity method in the large water tank. The comparisons show that their calibration results are in a good agreement with each other, and the maximum deviation is 0.7 dB. All these demonstrate that the wide-band signal processing technology described is accurate and stable.

Physical field of dual-frequency ultrasonic vibration and its effect on solidification behavior of MgZnY alloy

A three-dimensional model was established for coupled simulation of the physical field in a liquid subjected to dual-frequency ultrasonic vibration. The effect of sonotrode position, tip shape, and vessel on the distributions of acoustic pressure and acoustic streaming were clarified. The influence of physical fields on the solidification behavior of Mg alloy was investigated. The simulation results show that the interaction between the two ultrasounds was weakened as the sonotrode spacing increased, and the radiating angle had little effect on the acoustic pressure distribution. The volume mean pressure in the liquid radiated by the plane tip was the smallest, but with the greatest acoustic streaming intensity. In contrast, the spherical tip radiated the highest volume mean pressure in the liquid medium, but the acoustic streaming was severely suppressed. Attributed to the smooth spherical surface that facilitated fluid flow, high flow velocity could be achieved using a round-bottomed crucible without severe acoustic pressure attenuation. The experimental results show that cavitation and acoustic flow caused the coarse dendrites to turn into fine isometric crystals. The acoustic flow accelerated the melt flow and alleviated the segregation and precipitation of Zn elements, leading to a decrease in the content and size of the second phase in the billet.

Observation of acoustic meron textures

Merons, as a member of quasiparticle family characterized by half-integer of the skyrmion topological charge with nontrivial topological textures, are of great interest in various branches of physics. Here, we report the first experimental observation of a meron texture configuration in acoustic waves. A squared metastructure is designed to support the spoof acoustic surface wave, forming meron lattice patterns in the acoustic velocity field vectors. The experimental results indicate that the meron textures can be moved and shaped by tuning the phase and amplitude differences between the excited sound sources, respectively. To demonstrate the topologically protected character of meron against structure defects, we further measure the acoustic pressure and velocity field distributions on a defective surface. The acoustic meron texture not only provides potential applications toward topologically robust ways to manipulate vectorial characteristics of the acoustic waves but also instills confidence for exploring other members of the quasiparticle family, such as the acoustic hopfion in acoustic waves.

New insights into the influencing mechanism of ultrasonic vibration on interface of Al/Mg bimetal composites by compound casting using simulation calculation and experimental verification

In this work, the numerical simulation of acoustic pressure distribution in ultrasonic vibration-assisted compound casting of Al/Mg bimetal composites was conducted. Relevant experimental verification was also performed to understand the influence of ultrasonic vibration treatment (UVT) on the interfacial microstructures and mechanical properties of the Al/Mg bimetal composites. Results revealed that the acoustic pressure distributions in the AZ91D melt were related to the vibration frequencies. The effective cavitation area at the Al/Mg interface reached the maximum percentage of 95.6 %, with the ultrasonic frequency of 20 kHz. The experimental results found that the Al/Mg interface without UVT was composed of Al–Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) layer and eutectic layer. The oxide film and gas gap were existed between the two layers. The Mg2Si particles were gathered at the IMCs layer. The interfacial grains were coarse and their growth was directional. With UVT, the effective cavitation was occurred at the Al/Mg interface. The oxide film was broken, and the gas gap was eliminated. The interfacial microstructures were significantly refined. Due to the accelerated elemental diffusion and solute transfer by UVT, a more homogeneous Al/Mg interface was obtained. The Mg2Si particles were refined and formed at the eutectic layer. The microhardness mismatch of the IMCs layer and eutectic layer was decreased by UVT. The shear strength of the Al/Mg bimetal composites with UVT was enhanced to 62.2 MPa, which increased by 62.8 %, compared with that without UVT.

Numerical simulation of three physical fields in counter‐current ultrasound

AbstractPower ultrasound is a kind of green and environmentally friendly processing technology. Still, because of its uneven distribution of acoustic pressure in the propagation medium, the large‐scale industrial application of ultrasound is limited. In order to make more effective use of ultrasound waves, this paper uses a counter‐current ultrasound‐assisted extraction container as the geometric model of simulation, calculates the distribution of the acoustic pressure field in the container by COMSOL Multiphysics software, and investigates the effect of acoustic pressure on the fluid field, and temperature field. The simulation results showed that the acoustic pressure increased with the increase of ultrasound power and frequency, tended to balance with the rise of propagation distance, and the cavitation effect was more likely to occur. The propagation of ultrasound in the fluid medium increased the velocity and vorticity of the fluid, which was conducive to the generation of mixing effects. Under the ultrasound pulse working mode for 4 min, the fluid temperature on the central axis increased in a stepped order, with a maximum increase of 19.3°C. We can see that the establishment of the simulation model provides some theoretical guidance for the more practical application of ultrasound in the food industry.Practical ApplicationsThe limitation of ultrasound application mainly lies in the nonuniform distribution of acoustic pressure when ultrasound propagates in the fluid medium. Therefore, mastering the distribution of multiple physical fields in the reaction zone through simulation has important technical support and theoretical guiding significance for designing efficient ultrasound‐assisted extraction equipment and large‐scale industrial production of ultrasound.

Design Approaches and Electromechanical Modeling of Conformable Piezoelectric‐Based Ultrasound Systems

AbstractPainless, needleless delivery of drugs through the skin can be realized through aphenomenon called sonophoresis by applying an ultrasound field to the biological tissue. Development of wearable embodiments of such systems demands comprehensive characterization of both the physical mechanism of sonophoresisas well as wearability parameters. Here, we present a framework for analyzing disk‐type piezoelectric transducers in a polymeric substrate to create acoustic cavitation in a fluid coupling medium for sonophoresis applications. The device design and operating parameters such as the working frequency, applied voltage range, acoustic pressure distribution, and transducer spacing were determine dusing a finite element methods (FEM),and verified with experimental measurements. The influence of the surrounding water and tank reflections on the acoustic pressure field, and the interaction between the elements in the array structure were also studied.Finally, the impact of skin and the substrate geometry on the acoustic pressure fields was characterized to simulate the invivo use‐case of the system. These analytical models can be used to guide critical parameters for device design such as the separation distance of the piezoelectric transducer from the skin boundary. We envision that this tool boxwill support rapid design iteration for realization of wearable ultrasound systems.

Full Acoustic Analogy of the fluid-dynamics noise of an immersed cube

The estimation of fluid dynamic noise generated by anthropogenic sources in realistic marine basins and on land is paramount for human safety and environmental protection. Classical acoustic analogies have limited capabilities when considering the natural variability and peculiarities of the acoustic propagation domain. The Full Acoustic Analogy (FAA), based on the combination of an acoustic analogy for source characterization and a propagation model for far-field transmission, allows the estimation of detailed soundmaps, practical when assessing the risk associated with exposure to fluid-dynamic noise, both impulsive and continuous. The verification of the methodology, consisting of comparing of the far-field acoustic pressure signal obtained with the FAA and with the Ffowcs-Williams and Hawkings equation (classical acoustic analogy for moving immersed bodies), is proven for the first time for the quadrupole non-linear terms. The latter may contribute significantly to the total noise field at small-to-medium distances from the source. In conjunction, the ability of the FAA method to predict the acoustic pressure distribution within the three-dimensional propagation domain is highlighted.

Low-frequency air-coupled transducer based damage detection in composite materials

In this paper results of simulations of non-contact elastic wave generation in the composite panel based on acoustic to elastic wave transformation are presented. For this purpose simulations of acoustic wave generation and processing are based on the FEM method in COMSOL. Elastic wave generation and propagation are based on the spectral element method (SEM) in the time domain. The SEM model utilises time-varying acoustic pressure distributions calculated in the FEM. The SEM allows to simulate the interactions of elastic waves with the delamination. Damage localization is based on RMS elastic wave energy maps. In this research a panel made of carbon fibre-reinforced polymer composite is investigated. Research related to low-frequency air-coupled transducer (ACT) is presented. The utilisation of low-frequency waves allows for the reduction of the effects of the wave attenuation in composite material. The proposed combination of FEM and SEM gives an efficient tool for the simulation of non-contact wave generation for non-destructive testing analysis.

A Numerical Investigation of the Effect of Boundary Conditions on Acoustic Pressure Distribution in a Sonochemical Reactor Chamber

A Numerical Investigation of the Effect of Boundary Conditions on Acoustic Pressure Distribution in a Sonochemical Reactor Chamber

Quantitative photoacoustic tomography: modeling and inverse problems.

Quantitative photoacoustic tomography (QPAT) exploits the photoacoustic effect with the aim of estimating images of clinically relevant quantities related to the tissue's optical absorption. The technique has two aspects: an acoustic part, where the initial acoustic pressure distribution is estimated from measured photoacoustic time-series, and an optical part, where the distributions of the optical parameters are estimated from the initial pressure. Our study is focused on the optical part. In particular, computational modeling of light propagation (forward problem) and numerical solution methodologies of the image reconstruction (inverse problem) are discussed. The commonly used mathematical models of how light and sound propagate in biological tissue are reviewed. A short overview of how the acoustic inverse problem is usually treated is given. The optical inverse problem and methods for its solution are reviewed. In addition, some limitations of real-life measurements and their effect on the inverse problems are discussed. An overview of QPAT with a focus on the optical part was given. Computational modeling and inverse problems of QPAT were addressed, and some key challenges were discussed. Furthermore, the developments for tackling these problems were reviewed. Although modeling of light transport is well-understood and there is a well-developed framework of inverse mathematics for approaching the inverse problem of QPAT, there are still challenges in taking these methodologies to practice. Modeling and inverse problems of QPAT together were discussed. The scope was limited to the optical part, and the acoustic aspects were discussed only to the extent that they relate to the optical aspect.

Acoustophoresis of monodisperse oil droplets in water: Effect of symmetry breaking and non-resonance operation on oil trapping behavior.

Acoustic manipulation of particles in microchannels has recently gained much attention. Ultrasonic standing wave (USW) separation of oil droplets or particles is an established technology for microscale applications. Acoustofluidic devices are normally operated at optimized conditions, namely, resonant frequency, to minimize power consumption. It has been recently shown that symmetry breaking is needed to obtain efficient conditions for acoustic particle trapping. In this work, we study the acoustophoretic behavior of monodisperse oil droplets (silicone oil and hexadecane) in water in the microfluidic chip operating at a non-resonant frequency and an off-center placement of the transducer. Finite element-based computer simulations are further performed to investigate the influence of these conditions on the acoustic pressure distribution and oil trapping behavior. Via investigating the Gor'kov potential, we obtained an overlap between the trapping patterns obtained in experiments and simulations. We demonstrate that an off-center placement of the transducer and driving the transducer at a non-resonant frequency can still lead to predictable behavior of particles in acoustofluidics. This is relevant to applications in which the theoretical resonant frequency cannot be achieved, e.g., manipulation of biological matter within living tissues.

Acoustic Characteristics Analysis of Double-Layer Liquid-Filled Pipes Based on Acoustic–Solid Coupling Theory

Based on the theory of acoustic–solid coupling, the phase velocity-thickness product of a double-layer liquid-filled pipeline is analyzed, and the dispersion relationship between angular frequency and wavenumber–thickness product is analyzed, providing a theoretical basis for ultrasonic guided wave detection. The wave number analytical expression of the double-layer liquid-filled pipeline is constructed, and the dispersion relationship of the double-layer liquid-filled pipeline under different frequency–thickness products and wavenumber–thickness products is calculated through parameter scanning. The dispersion curves of the double-layer liquid-filled pipeline are numerically analyzed in the domains of pressure acoustics, solid mechanics, and acoustic–solid coupling. The numerically simulated dispersion curves show high consistency with the analytically calculated dispersion curves. The analysis of the phase velocity frequency–thickness product indicates that the axial mode dispersion curves of the pipe wall decrease with the increase in frequency–thickness product in the coupling domain, and then tend to be flat and intersect with the radial mode dispersion curves in the coupling domain; these intersection points cannot be used for ultrasonic guided wave detection. The T(0,1) mode dispersion curve in the coupling domain of the pressure acoustics domain remains smooth from low frequency to high frequency. It is found that the dispersion curves of the phase velocity frequency–thickness product, angular frequency wavenumber–thickness product, and the acoustic pressure distribution map of the double-layer liquid-filled pipeline based on acoustic–solid coupling can provide theoretical support for ultrasonic guided wave detection of pipelines.

Dynamics of droplets entering ultrasonic standing wave field at different angles

We, herein, present dynamic behaviors of droplets entering an ultrasonic standing wave field (19 800 Hz) at different angles. In experiments, droplets’ motion is recorded by using a high-speed camera, and an in-house Python program is used to obtain droplet positions and morphological characteristics as functions of time. The experimental results indicate that when the sound intensity is lower than the instability intensity and higher than the levitation intensity, the vertically falling droplet will oscillate up and down based on the equilibrium position. Although the oscillation amplitude decays from 0.52Tl to 0.01Tl (Tl = λ/2, λ is the wavelength) under the action of viscous resistance, the oscillation frequency of the droplet remains unchanged. Meanwhile, as the droplet’s position oscillates, the acoustic radiation force on the droplet also periodically fluctuates, resulting in the acoustically forced oscillation of the droplet shape. In addition, when the droplet enters the sound field with a horizontal tilt angle θ of 15°, it undergoes a V-shaped translational motion, first descending and then ascending. As the sound pressure amplitude increases, the rebound position of the droplet advances. When the sound pressure amplitude reaches the instability value (7900 Pa), the droplet undergoes right-hand and left-hand disintegration during its descent and ascent, respectively. This instability is due to the acoustic radiation pressure distribution and the droplet’s V-shaped trajectory. This work comprehensively discussed the complex motion of moving droplets in the acoustic standing wave field, which may inspire revealing the spray motion in the liquid engine with high-intensity resonance.

Flow and heat transfer through a porous tumor during high-intensity focused ultrasound

High-intensity focused ultrasound (HIFU) represents a non-invasive approach for localized treatment, wherein focused ultrasound waves are applied to specific tissues. However, accurately targeting the HIFU ablation area is still a challenge. The difference in the physical properties of the tumor being treated, compared to normal tissue, particularly, porosity, is an essential aspect that may influence the effectiveness of treatment. This study investigated the impact of tumor porosity, acoustic operating frequency, and the tumor acoustic absorption coefficient on fluid flow and temperature distribution in both the porous tumor and surrounding tissue during HIFU exposure using numerical models. Furthermore, the study examined the differences in porosity between normal and tumor tissues and the resulting phenomena. To determine the acoustic pressure, flow velocity, and temperature distributions in the porous tumor during HIFU treatment, researchers have employed numerical modeling to calculate acoustic wave propagation, fluid flow, and heat transfer processes. This study indicates that the maximal temperature increase might not always necessarily occur at the acoustic pressure focus, particularly, if the tumor does have a higher porosity than the neighboring normal tissue. This was because the flowing fluid of the tumor and adjacent tissues had a substantial impact on the strong convection in the focus area. These findings highlight the significance of this study in terms of precisely localizing the HIFU ablation target region and ensuring minimal thermal injury to the surrounding healthy tissue.

Side Effect of the Use of Acoustic Barriers Observed in the Infra Range

Acoustic barriers which are positioned along traffic lanes are designed to protect the surroundings from excessive noise. Such structures are to reverberate, diffract and damp the propagating acoustic waves. However, this method of shielding has some disadvantages which include constraint visibility and structure-born noise. The interaction between traffic-caused movement of air mass and acoustic barriers may generate infra noise waves. That is undesirable and should be estimated. The authors undertook the research to diagnose the plausible side effect of structure-born noise of such barriers because it may influence human body (Kasprzak, 2014). As a mechanical structure, the acoustic barrier is characterized by mechanical parameters which, in the field of modal analysis, are made up of natural frequencies, damping factors and mode shapes. In this paper the authors investigated the acoustic pressure distribution in the neighborhood of a real acoustic barrier in the scope of infra noise propagation. The methods of modal analysis were used to identify natural frequencies of the barrier and dominating frequencies of propagating waves in the far field. The correlation between observed vibration and acoustic signals is presented.

Numerical simulation of dynamic characteristics of hydrofoil structure under cavitation conditions

In this paper, the effects of different cavitation bubble on the natural frequency, mode shape and hydrodynamic damping of the NACA0009 hydrofoil are investigated by numerical simulation method. The cantilever truncated hydrofoil model is set in a high-speed water tunnel. The dynamic characteristics of the hydrofoil structure is affected by the fluid-structure coupling. Compared to the properties of water, the density of cavitation bubbles decreases, causing an increase in the natural frequency of the structure, and the decrease in the speed of sound also causes a change in the mode shape. The growth rate of frequency under unit chord length cavitation is nonlinear as the cavitation bubble length increases. By defining a modal displacement function to compare the structural mode shapes, cavitation intensifies the bending and torsional deformation of the hydrofoil. Even if the volume of cavitation bubbles is small, the inhomogeneous distribution of acoustic pressure and changes in cavitation bubble properties can cause changes in the structural mode shapes. The one-way FSI numerical method for hydrodynamic damping in cavitating flow is established and the applicability of this method is verified by the calculation of damping in water. For the first bending mode fc1, the hydrodynamic damping with 50% chord length (0.5lc) stably attaching cavitation is simulated. As the length of the cavitation bubble increases to 0.8lc, the damping value becomes smaller. The research in this paper lays the foundation for analysing the dynamic characteristics of hydraulic machinery with cavitation using numerical simulation method.