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As elastography, an emerging medical imaging strategy, advances, surface acoustic waves have been utilized to examine superficial tissues quantitatively. So far, most studies are experimental, and a numerical method is needed to cost-effectively investigate surface acoustic wave generation and propagation for technical development and optimization purposes. This study aims to develop a reliable numerical method for simulating impulse-induced surface acoustic waves using the k-wave simulation toolbox. According to the physical process of surface acoustic wave based elastography, the proposed simulation method consists of two stages: compressional wave simulation and elastic wave simulation, which aim to generate acoustic radiation force impulse and elastic waves, respectively. The technical procedures were demonstrated by a wave simulation on a water–tissue model. Meanwhile, three acoustic radiation force modeling methods were adopted. The compressional wave simulation showed that the three force modeling methods could produce similar force distribution in space but largely different amplitudes. The elastic wave simulation confirmed the feasibility of numerically generating surface acoustic waves. The reliability of the simulated waves was verified by a quantitative comparison between the numerically acquired sound speeds and their theoretical expectations and by a qualitative comparison between the numerically generated waves and the experimental observations under similar conditions. In summary, this study confirms k-wave as an effective numerical method for simulating surface acoustic waves for elastography purposes. This study provides an immediate simulation platform for investigating Scholte waves, the surface acoustic wave at a liquid–solid interface, and also, a potential numerical framework to investigate other surface acoustic waves. [ABSTRACT FROM AUTHOR]

Acoustic black hole (ABH), as a new wave manipulation technique, shows excellent applications in vibration and noise reduction of structures. Nowadays, most ABHs use materials with a fixed elastic modulus, limiting their low-frequency performance. Herein ABH plates with variable elastic modulus (VM-ABH) is designed, and its vibration and acoustic radiation characteristics are investigated by using numerical analysis. The results show that the vibration response of VM-ABH has a decrease of 5–13.2 dB relative to that of the uniform texture ABH (UT-ABH) in the frequency range of 10–5000 Hz, and the degree of energy aggregation is significantly improved. Moreover, the sound pressure level was reduced by 3.6 dB. Meanwhile, by linearly varying the elastic modulus in the center region of the VM-ABH, the effects of gradient index and terminal elastic modulus on the damping characteristics and dynamic response are revealed. The research results provide new objects for the study of vibration and noise reduction of ABH. [ABSTRACT FROM AUTHOR]

The control of the drag, noise, and vibration of underwater vehicles has always been a hot topic, causing the study of skin with multiple functions to become a development trend. In the present paper the vibration isolation and sound radiation reduction characteristic of a multiple functions skin, micro-floating raft array skin (MFRAS), are assessed by a mathematical model. The mathematical model is developed based on the thin plate theory and the effective medium theory and validated by the finite element model and reference. The structural parameters of MFRAS have been discussed and optimized by orthogonal experiment design with the evaluation index, the average value of the mean square velocity level. The results show that the MFRAS can isolate the vibration transmission of internal equipment by mismatched impedance between MFRAS and plate, and then reduce the sound radiation. The optimized MFRAS can reduce the mean square velocity level by 1.35 dB and the sound radiation power level by 2.47 dB within the frequency range of 10–2000 Hz compared with the equal weight free damping layer. [ABSTRACT FROM AUTHOR]

The tire/road noise is one of the major problems facing the tire industry due to the nuisance felt by the vehicle's driver and passengers. Moreover, it is expected in the coming years that this sound nuisance will be one of the main sources of vehicle noise due to the transition from combustion engine driven vehicles to electric vehicles. Tire manufacturers have therefore refined the design of their tire structures to find technological solutions to reduce traffic noise. Tire/road noise is also generated by various mechanisms which depend on different parameters such as the properties of the tire, road texture and driving conditions. This noise is partly caused by the acoustic radiation induced by the tire vibrations due to contacts with the road. The simulation and analysis of the tire's vibrations remains a challenge for the tire industry. Indeed, the simulation of the full dynamic response of a rolling patterned tire requires not only taking onto account various nonlinearities but also the multi-scale nature of the generated dynamic response. Contrary to a straightforward strategy that consists in using a time integrator to predict the multi-scale dynamic response, the strategy proposed in this study is based on a two-step approach to separate the dynamics occurring at different scales. The mathematical formulation of the proposed method is detailed as are the different modeling choices to simulate tire rolling under imposed load. The sensitivity of the tire's vibrations response is analyzed under different rolling conditions and with respect to certain key tire tread pattern parameters. • An adapted two-step approach to simulate nonlinear vibrations by separating the dynamics occurring at different scales. • Mathematical formulation of the proposed method with different modeling choices to simulate tire rolling under imposed loads. • Application to patterned tires rolling on a smooth surface. • Examples of the tire's vibrations response under different rolling conditions and key tire tread pattern parameters. [ABSTRACT FROM AUTHOR]

Aiming at the low-frequency line spectrum noise characteristics of power equipment noise, based on the principle of energy degradation, this paper combines the energy degradation sound insulation structure with the dynamic vibration absorption technology for the first time and applies it to the research field of noise control of power equipment in substations. Dynamic vibration absorption technology is used to effectively control low-frequency vibration and noise. Considering that there is an upper limit to the capacity of DVA, the sound-vibration energy degradation design of the transformer is completed by setting a sound insulation structure on the outside of the original transformer housing. It is analyzed that the vibration energy of the sound insulation structure in the specific frequency band is significantly reduced compared to the transformer housing, realizing efficient degradation of the vibration energy of the transformer housing and effective isolation of sound radiation. Through the optimized design of dynamic vibration absorption for the sound insulation structure, the structural sound isolation ability at the target frequency is further strengthened, and the system noise radiation level is greatly reduced under the action of multiple mechanisms at the target frequency, verifying the feasibility and high efficiency of the optimal DVAs energy degradation design of the transformer. [ABSTRACT FROM AUTHOR]

AbstractIn the present work, an iterative eigenvalue method (IEM) is proposed and combined with the boundary element method (BEM) to perform the structural acoustical analysis of the orthotropic steel deck (OSD) damped with constrained layer damping (CLD), through which the frequency-dependent properties of the viscoelastic core can be accurately considered. Then, a series of hammer tests are carried out in a semi-anechoic chamber to verify the acoustic prediction method. It shows that the simulated structural noises basically agree with the test results, and the overall deviations at the field points M2 and M8 are merely 2.4 and 2.3 dB, respectively. Subsequently, taking the thicknesses of the damping layer and the constraining layer, as well as the material properties of the constraining layer as design variables, a central composite experiment is designed and combined with response surface methodology (RSM) to fit the relationship between analysis objectives and design variables. With the objective of minimizing the acoustic radiation power, a program for finding the optimal values of design variables is developed based on the interior penalty function method. Through iterative computations, the optimal points are numerically determined as t1 = 2.3 mm and t2 = 0.3 mm for the thicknesses of the damping layer and the constraining layer, respectively. Steel alloy is found to be the optimal material for the constraining layer. After optimizing CLD treatment, the overall acoustical power level can be reduced from 97.7 dB to 93.1 dB and the overall sound pressure levels (SPLs) at the field points M2 and M8 can be reduced from 89.2 dB to 83.5 and 76.9 dB to 70.3 dB, respectively, indicating that the optimization of CLD design parameters can significantly improve acoustic performance of the CLD-damped structures. [ABSTRACT FROM AUTHOR]

Compared with traditional honeycomb and stiffened sandwich structures, lattice-based structures are considered an ideal substitute for traditional core structures due to their high stiffness and other potential multifunctional application characteristics. Based on that, the sound radiation characteristics of the sandwich plate with different truss cores under structure borne excitation were investigated in the current paper, wherein three truss cores, including pyramidal, tetrahedral and 3D-kagome cores types, are considered. The governing equations for the vibration and sound radiation analysis of the sandwich plate structure are carried out using the static equilibrium method, and then solved via the Navier approach and Rayleigh integral. By comparing the experimental results, the validity of the proposed theoretical model is verified. The theoretical model is subsequently used to investigate the influences of truss core geometric parameters and types, face sheet-core face sheet thickness ratio and aspect ratio on sandwich plate sound radiation characteristics. The results indicate that, in the range [ 5 ∘ ≤ θ ≤ 52 ∘ ] and [ 52 ∘ < θ ≤ 85 ∘ ] , the tetrahedral and 3D-Kagome core types have the maximum natural frequency values, respectively, while the resonance peaks of sound pressure level curves move to lower frequency region with the increase in truss core radius and face sheet-core face sheet thickness ratio, and the sandwich plate with the 3D-kagome core shows better sound radiation characteristics in the wide frequency range. [ABSTRACT FROM AUTHOR]

With the increasing number of complex well types in the development stage of oil and gas fields, it is becoming increasingly urgent to use remote detection logging while drilling (LWD) to explore the geological structures in a formation. In this paper, the feasibility and reliability of the dipole remote detection of logging while drilling are demonstrated theoretically. For this purpose, we use an asymptotic solution of elastic wave far-field displacement to derive the calculation formula for the radiation pattern and energy flux of an LWD dipole source. The effects of influencing factors, including the source frequency, formation property, drill collar size, and mud parameter, on the radiation pattern and energy flux are analyzed. The results show that the horizontally polarized shear wave (SH-wave) has a greater advantage in imaging the reflector compared with the cases of the compressive wave (P-wave) and vertically polarized shear wave (SV-wave), which indicates the dominance of the SH-wave in dipole remote detection while drilling. The optimal source excitation frequency of 2.5 kHz and inner and outer radii of the drill collar of 0.02 and 0.1 m, respectively, should be considered in the design of an LWD dipole shear wave reflection tool. However, the heavy drilling mud is not conducive to remote detection during logging while drilling. In addition, the reflection of the SH-wave for the LWD condition is simulated. Under the conditions of optimal source frequency, drill collar size, and mud parameters, the reflection of the SH-wave signal is still detected under the fast formation. [ABSTRACT FROM AUTHOR]

Different coal failure impact types exhibit different damage statuses and failure modes, resulting in distinct signal characteristics of infrared radiation (IR) and acoustic emission (AE). This paper combines IR and AE monitoring methods to innovatively establish coal damage and failure precursor warning models and obtains the IR and AE precursor characteristics for different coal failure impact types. This research shows that there is a good correspondence between IR and AE timing and spatial distribution of different coal impact types. As the impact tendency increases, the intensity of IR and AE signals increases with coal failure, and the AE positioning points and IR high-temperature areas tend to concentrate. The coal body gradually changes from tensile failure to shear failure. The shear cracks in the failure stage of coal with no, weak, and strong impact are 39.9%, 50.9%, and 53.7%, respectively. The IR and AE instability precursor point of coal with no, weak, and strong impact occurred at 55.2%, 66.3%, and 93.4% of coal failure, respectively. After the IR and AE combined instability precursor point, the dissipated energy and combined damage variable increase rapidly, and the coal body will undergo instability and failure. The research results provide a theoretical basis for comprehensive monitoring of coal body failure and rock burst. [ABSTRACT FROM AUTHOR]

The fault diagnosis of rolling bearing acoustic radiation signals holds significant importance in industrial equipment maintenance. It effectively prevents equipment failures and downtime, ensuring the smooth operation of the production process. Compared with traditional vibration signals, acoustic radiation signals have the advantage of non-contact measurement. They can diagnose faults in special conditions where sensors cannot be installed and provide more comprehensive equipment status information. Therefore, to extract the fault characteristic information of rolling bearings from complex acoustic signals, this paper proposes an advanced deep learning model combining Gramian Angular Field (GAF), ResNet1D, ResNet2D, and multi-head attention mechanism, named CRAMNet (Combined ResNet Attention Multi-Head Net), to diagnose the faults of rolling bearing acoustic radiation signals. Firstly, this method includes converting one-dimensional signals into GAF images and performing data standardization and segmentation. Then, the method utilizes ResNet1D to extract features from one-dimensional signals and ResNet2D to extract features from GAF images. Further, it combines the multi-head attention mechanism to enhance feature representation and capture dependencies between different channels. Finally, this paper compares the proposed method with several traditional models (including CNN, LSTM, DenseNet, and CNN-Transformers). Experimental results show that the proposed method performs outstandingly in terms of accuracy and robustness. The combination of residual networks and multi-head attention mechanism in the model significantly enhances its ability to accurately diagnose rolling bearing faults, proving the superiority of the algorithm. [ABSTRACT FROM AUTHOR]

Microplastics have emerged as ubiquitous contaminants, attracting increasing global attention. Recent evidence confirms the presence of microplastics in human blood, suggesting their potential to interact with cells and induce adverse physiological reactions in various organs as blood circulates. To quantify the distribution of microplastics and assess their potential effects on human health, the effective separation of microplastics from blood is crucial. However, current methods for separating microplastics from blood are limited in effectiveness and simplicity. This study proposes a microfluidic device that utilizes traveling surface acoustic waves to separate microplastics from blood. While traveling surface acoustic waves have been employed to separate various particles, a systematic study on the separation of microplastics from blood samples has not been previously reported. Specifically, the theoretical values of the acoustic radiation factor for various types of microplastics and blood cells were investigated. The significant differences in resonant frequencies indicated the feasibility of separating microplastics of different sizes and types from blood cells. Experimental validation was performed using a polydimethylsiloxane microfluidic device on a piezoelectric lithium niobate substrate. The device successfully separated 5- and 10-micrometer polystyrene microplastics from blood samples. The effects of power and flow rate on separation efficiency were also systematically investigated. This study provides a novel approach for the effective separation of microplastics from blood, contributing to the assessment of their distribution and potential health impacts. [ABSTRACT FROM AUTHOR]

The longitudinal fluctuating forces of a propeller are a major cause of sound radiation of an underwater vehicle in the low frequency range. A hydraulic leveraged dynamic anti-resonance vibration isolator (HLVI) is proposed to attenuate the longitudinal vibration of a shaft system transmitted to the hull. The semi-analytical model of the shafting system with and without the isolator is set up by employing the frequency response synthesis method, in which the elasticity of the foundation is taken into consideration. Compared to the traditional isolation scheme and DVA, the proposed control scheme will not change the longitudinal effective stiffness and needs a small mass to attenuate the longitudinal vibration of the shafting system. A parametric study was conducted to investigate the key parameters of the isolator and their impact on its isolation performance. An experimental apparatus is set up to validate the isolation scheme. The acceleration frequency response results of the shafting system under axial excitation with both the frequency sweep method and discrete sinusoidal frequencies are presented and discussed. The results indicate that the proposed method is capable of attenuating the corresponding longitudinal vibration of the shafting system. [ABSTRACT FROM AUTHOR]

Unlike uncertainties stemming from loads and material properties, interface uncertainties arising from variations in immersed media within the acoustic field can significantly alter the solution domain, leading to substantial dispersion in radiated acoustic pressure. To address this issue, this study introduces the extended finite element method (XFEM), Dirichlet-to-Neumann (DtN), and direct probabilistic integration method to develop a two-dimensional stochastic acoustic radiation analysis approach for systems with immersed media interface uncertainties. The XFEM with DtN enables accurate capture of the non-smooth solutions at the interface by constructing enriched functions without modifying the original mesh and allows the introduction of random parameters to describe the interface modifications. The input probability space of the parameters is partitioned and the Dirac δ function is smoothed, and the statistical properties such as the probability density function of system responses are obtained by summing the response under each representative point, which can efficiently treat the propagation of interface uncertainties. The computational performance of the proposed scheme is validated using examples of infinite oscillating rigid cylinders and submarine acoustic radiation. Furthermore, the impact of parameters such as the position and thickness of porous material domains on the radiated acoustic pressure is discussed. [ABSTRACT FROM AUTHOR]

Aiming to address the significant external noise produced by helicopter rotors, an integrated process based on acoustic modes has been developed for predicting the global noise footprint. The proposed method has the advantages of global prediction, analysis, and low computational costs. The key steps involve constructing an acoustic modal database and efficient prediction of noise footprint. First, the global noise model is utilized to map the time-domain sound pressure to amplitudes and coefficients in the acoustic modal domain. Acoustic mode coefficients representing various flight states are systematically cataloged in the database. Subsequently, the coefficients are extracted based on the characteristic parameters of trajectory elements, allowing for the evaluation of noise radiation in the acoustic modal domain. To investigate the impact of descent angle and advance ratio on the noise footprint, a simulation study is conducted in the forward and approach flight with an AS350 helicopter. Results indicated that, for a region with 1800 observers, the computational time of the developed approach requires only one-fifth of the time compared to the traditional Rotorcraft Noise Model method. This remarkable reduction in computation time, along with the global predictive capability, supports the practicality of efficient noise footprint assessment in both military and civilian contexts. [ABSTRACT FROM AUTHOR]

Recently, capacitive micromachined ultrasound transducers (CMUTs) with long rectangular membranes have demonstrated performance advantages over conventional piezoelectric transducers; however, modeling these CMUT geometries has been limited to computationally burdensome numerical methods. Improved fast modeling methods, such as equivalent circuit models, could help achieve designs with even better performance. The primary obstacle in developing such methods is the lack of tractable methods for computing the radiation impedance of clamped rectangular radiators. This paper presents a method that approximates the velocity profile using a polynomial shape model to rapidly and accurately estimate radiation impedance. The validity of the approximate velocity profile and corresponding radiation impedance calculation was assessed using finite element simulations for a variety of membrane aspect ratios and bias voltages. Our method was evaluated for rectangular radiators with width:length ratios from 1:1 up to 1:25. At all aspect ratios, the radiation resistance was closely modeled. However, when calculating the radiation reactance, our initial approach was only accurate for low aspect ratios. This motivated us to consider an alternative shape model for high aspect ratios, which was more accurate when compared with FEM. To facilitate the development of future rectangular CMUTs, we provide a MATLAB script that quickly calculates radiation impedance using both methods. [ABSTRACT FROM AUTHOR]

The manipulation of acoustic waves is becoming increasingly crucial in research and practical applications. The coordinate transformation methods and acoustic metamaterials represent two significant areas of study that offer innovative strategies for precise acoustic wave control. This review highlights the applications of these methods in acoustic wave manipulation and examines their synergistic effects. We present the fundamental concepts of the coordinate transformation methods and their primary techniques for modulating electromagnetic and acoustic waves. Following this, we deeply study the principle of acoustic metamaterials, with particular emphasis on the superior acoustic properties of polymers. Moreover, the polymers have the characteristics of design flexibility and a light weight, which shows significant advantages in the preparation of acoustic metamaterials. The current research on the manipulation of various acoustic characteristics is reviewed. Furthermore, the paper discusses the combined use of the coordinate transformation methods and polymer acoustic metamaterials, emphasizing their complementary nature. Finally, this article envisions future research directions and challenges in acoustic wave manipulation, considering further technological progress and polymers' application potential. These efforts aim to unlock new possibilities and foster innovative ideas in the field. [ABSTRACT FROM AUTHOR]

Purpose: Liver stiffness measurement (LSM) by transient elastography has been shown to underperform in high-risk varices (HRVs) prediction in obese non-alcoholic fatty liver disease (NAFLD) compensated cirrhosis (CC). LSM by magnetic resonance elastography (MRE) and acoustic force radiation impulse (ARFI) has been shown to be useful in prediction of oesophageal varices (EVs), but has limited evidence in obese NAFLD-CC. Methods: Obese patients with NAFLD-CC who underwent MRE and ARFI for LSM and endoscopy for screening of varices were enrolled. Performance of MRE and ARFI for predicting EVs or HRVs was evaluated using area under receiver operating characteristics (AUROC) curves and regression analyses were performed for predictor variables. Results: One hundred eight patients [mean age 54.7 ± 9.6 years, median BMI, 28.5 (26.4–30.0) kg/m2. 72.2% diabetics, 45.4% hypertensive] were enrolled. Fifty-two (48.1%) had no varices, while 29 (26.8%) and 27 (25%) had low-risk varices (LRVs) and HRVs, respectively. MRE-LSM was higher in patients with LRVs (p = 0.01) or HRVs (p = 0.001) against those without varices. ARFI-LSM did not differ significantly between those without and with LRVs or HRVs (p > 0.05 for all). There was a low correlation between ARFI-LSM and MRE-LSM in the overall cohort (r = 0.19). Only platelet count (PC) [0.98 (0.97–0.99)] and MRE-LSM [1.8 (1.26–2.79)] were predictors of HRVs. At a cut-off of 4.75, MRE showed a sensitivity of 96.3%. Model combining MRE-LSM with PC had a diagnostic AUROC of 0.77 and 0.76 for EVs and HRVs. Conclusion: In obese NAFLD-CC, MRE-LSM is significantly higher in patients with varices. MRE combined with PC predicts EVs and HRVs with better accuracy than ARFI. [ABSTRACT FROM AUTHOR]

A limited number of studies investigate the effects of the neck design on the loudness and radiation of string instruments. In the related literature, it is assumed that the neck serves as a fingerboard and has little or no impact on sound production and radiation for string instruments, although there is no scientific evidence. By redesigning the neck of string instruments, we increased the air volume of the soundbox and vibrating surface area of string instruments. This study investigated the effects of two experimental (patented) neck designs on sound radiation and the perceived loudness of the baglama, a stringed instrument. The primary hypothesis of this research is that compared to traditional neck, the experimental neck designs increase the stringed instrument's air volume and vibrating surface area, thereby contributing to sound production and radiation efficiency, and perceived loudness. Sound radiation analysis based on acoustic modal analysis and psychoacoustic analysis were conducted. First, sound radiation measurements were made in an experimental setup. The data were then examined using the Frequency Response Function (FRF). The results revealed that the experimental necked baglamas' sound produced and radiated better than the traditional one. Second, listening (N=38) and playability (N=26) tests were conducted in focus group interviews. The participants listened to or played traditional and experimental necked baglamas and rated their loudness. The Friedman and Wilcoxon signed-rank test on the scores indicated that the participants perceived the experimental necked baglamas as significantly louder than the traditional one. Most participants stated that the experimental necked baglamas sounded higher and had better quality than the traditional one. Psychoacoustic findings corroborated the results of sound radiation analysis. [ABSTRACT FROM AUTHOR]

The issue of low-frequency structural noise radiated from high-speed railway (HSR) box-girder bridges (BGBs) is a significant challenge worldwide. Although it is known that vibrations in BGBs caused by moving trains can be reduced by installing multiple tuned mass dampers (MTMDs) on the top plate, there is limited research on the noise reduction achieved by this method. This study aims to investigate the noise reduction mechanism of BGBs installed with MTMDs on the top plate. A sound radiation prediction model for the BGB installed with MTMDs is developed, based on the vehicle–track–bridge coupled dynamics and acoustics boundary element method. After being verified by field tested results, the prediction model is employed to study the reduction of vibration and noise of BGBs caused by the MTMDs. It is found that installing MTMDs on top plate can significantly affect the vibration distribution and sound radiation law of BGBs. However, its impact on the sound radiation caused by vibrations dominated by the global modes of BGBs is minimal. The noise reduction achieved by MTMDs is mainly through changing the acoustic radiation contributions of each plate of the bridge. In the lower frequency range, the noise reduction of BGB caused by MTMDs can be more effective if the installation of MTMDs can modify the vibration frequency and distribution of the BGB to avoid the influence of small vibrations and disperse the sound radiation from each plate. [ABSTRACT FROM AUTHOR]

AbstractThis paper studied the vibro-acoustic characteristics of functionally graded sandwich plate in hygrothermal environment, where the core layer is composed of functionally graded materials with viscoelasticity. The viscoelastic behavior of the materials is described by a linear standard solid viscoelastic model, and the viscoelastic parameters are dependent of the frequency. Based on the first-order shear deformation theory and the linear deformation, the dynamic governing equation and acoustic formulas are established. By solutions the complex frequency, sound insulation and acoustic radiation responses of the plate are obtained. Then the effects of parameter variations on the vibration and acoustic performances are analyzed. [ABSTRACT FROM AUTHOR]

This study aims at the controllability of acoustically manipulated non-contact aggregation of bi-particle. Based on the acoustic wave radiation model of the transducer and the acoustic wave interference theory, the mathematical model between the spatial levitation point and the phase of the phased array ultrasonic array unit is established. A double-sided phased array test system was developed and the phase calculation algorithm for independently manipulating bi-particle was optimized. The algorithm is capable of independently distributing the energy applied to each levitation point. Through simulation and experiment, the horizontally aggregation characteristics of two levitated particles are investigated, and a interesting relationship between particles aggregation and standing wave phase difference is revealed, which follows the law of "attraction in the same phase but repulsion in the opposite phase". By adjusting the tilt angle of the standing wave acoustic trap, the critical distance when particles to accelerate and collision is sharply reduced from 1.5λ to 0.5λ, which provides a new perspective and potential application path for acoustic manipulation technology. [ABSTRACT FROM AUTHOR]

This paper presents the thermo-acoustic frequency response of an un-baffled rectangular panel subjected to an external excitation load. A boundary element method BEM has been employed taking into account the Kirchhoff-Helmholtz K-H integral equation for the acoustic pressure and with the fluid-plate interface boundary condition the acoustic pressure jump over the panel is calculated. The thermal effects are considered regarding in the form of a uniform increment of temperature of the panel and are analysed in order to prevent the buckling phenomena. The excitation force considered is in the form of a concentrated load at some point of the panel and the deformation modes correspond to the vacuum case. Applying a collocation method for the panel equation, a frequency transfer function is obtained that relates the deflexion of the panel with the applied load. The effect of several geometric parameters, different thermal loads and location of the load applied on the acoustic radiated power and the acoustic efficiency spectrum are evaluated. Furthermore, the influence of the excitation frequency on the sound directivity is evaluated. The verification of the method is proven with other works. [ABSTRACT FROM AUTHOR]

The Burton-Miller method is widely used to solve the problem of solution non-uniqueness in a conventional boundary element method (CBEM). Although this method is very robust, the hypersingular integral kernel contained in its normal derivative equation increases the computational complexity and reduces the computational accuracy. In this paper, a coupled double boundary Burton-Miller method with unique solutions at full wave numbers is proposed. The aforementioned process is done by replacing the normal integral equation of the Burton-Miller method with the virtual indirect boundary element method (VIBEM) integral equation of combined layer potential and using the equivalent relationship between their coefficient matrices. The proposed method inherits the high-precision advantages of VIBEM and avoids the hypersingular integrals of traditional Burton-Miller methods. In particular, no singular integral is present when the plane element is used for discretization. The numerical results of acoustic radiation and scattering show that the calculation accuracy of the coupled double boundary Burton-Miller method is higher than that of CBEM and the conventional Burton-Miller method. Moreover, the condition number of the coefficient matrix is much lower than that of VIBEM. Lastly, the computation time is less than that of the conventional Burton-Miller method. • Avoiding the calculation of hypersingular integrals in the Burton-Miller method. • Significantly improved the computational accuracy of the Burton-Miller method. • The non-uniqueness of the solution of the boundary integral equation is overcome. • The matrix condition number of the virtual boundary element method is reduced. [ABSTRACT FROM AUTHOR]

The study of acoustic radiation from spherical sound sources plays a crucial role in understanding the thermoviscous effects in practical acoustic problems. However, finding a general solution of acoustic radiation from spherical sound sources in thermoviscous fluids remains a formidable challenge. To advance this issue, an analytical method is developed in this paper to calculate the acoustic field radiated by spherical sound sources with the isothermal boundary condition and arbitrary velocity boundary condition. The developed method is utilized to present the solutions of the acoustic field generated by an oscillating sphere and a general spherical sound source, and the accuracy and validity of these solutions are verified through analytical and numerical methods. [ABSTRACT FROM AUTHOR]

Among the variety of methodological tools available for quantifying the degree of nasalization, nasometry has remained a popular choice for both academic and clinical research on speech due to its relatively low cost, portability, ease of use, and interpretability. In its simplest form, nasometry involves two microphones that independently capture the acoustic radiation from the mouth and nose. Recently, a method was proposed by Stewart and Kohlberger [(2017). Lang. Doc. Conserv. 11, 49–80] of using earbuds to achieve a similar result. Although the method has been widely used since, most notably in the context of linguistic fieldwork, it has yet to be tested against ground-truth measurements of acoustic nasalance from a commercially established device; the current study attempts to provide this ground-truth comparison. A wide variety of characteristics of the relationship between nasalance measurements created using acoustic data co-registered from a commercial nasometer, silicone earbuds, and flat earbuds are thoroughly examined. The results suggest that the "earbuds method" may provide reliable estimates of nasality when assessed at a global level (i.e., overall averages, relatively high/low nasalance scores coinciding with the presence/absence of nasalization), but that the accuracy of these estimates may decline at more fine-grained levels in different ways that are outlined in the discussion. [ABSTRACT FROM AUTHOR]

Previous field experiments support the claim that a tornado can radiate discernible infrasound between 0.5 and 10 Hz. The physical mechanisms of tornado sound generation are still not fully understood, although several potential mechanisms have been proposed. In this paper, the theory of vortex sound is applied to the sound radiation from two numerical tornado simulations based on large eddy simulations. There are two different vortex-related mechanisms in distinct frequency regimes. It is found that rotation of a non-axisymmetric vorticity field produces low-frequency infrasound less than 2.0 Hz. High-frequency tornado infrasound can be attributed to more complex vortex dynamics such as vortex merging. [ABSTRACT FROM AUTHOR]

A correlation-enhanced event-driven decomposition (CEED) method is developed to analyze the coherent structure during the acoustic burst in subsonic jets. To sample the acoustic burst signal for the CEED, a conditional filter is proposed. The correlation between the acoustic burst signal and the signal from the flow field is introduced into the decomposition, to deal with the low signal-to-noise ratio issue between these two signals. Suitability for the subsonic jets is demonstrated for the CEED, based on validated large eddy simulation results. Then, the short-time evolution of the coherent structure is analyzed by the CEED. The results show that the sampled acoustic burst signal is intermittent. Its spectrum appears the same shape as that of the original signal. Thus, the acoustic burst is dominant in the sound radiation. The correlation is found to accelerate the convergence of the CEED. The leading mode of the CEED is shown able to represent the short-time evolution of the coherent structure clearly. During the acoustic burst, the leading mode appears as a train of puffs, and it presents three stages: (1) Two in-phase puffs enclose an anti-phase puff. These puffs move downstream with their size growing. (2) The anti-phase puff vanishes, while the two in-phase puffs merge into a large puff. The large puff forms a wavefront. (3) Three puffs form waves in sequence. Together, these waves compose a train of waves. The merging accelerates the puff into a supersonic state intermittently; therefore, the merging is responsible for the acoustic burst. [ABSTRACT FROM AUTHOR]

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The mouth of a speaker is generally close to the microphones of speech communication devices, such as headsets and phones, whereas noise sources are more distant from the microphones. Hence, near-field enhancement using microphone arrays is a promising strategy for noise suppression. This study deals with radiation mode–based microphone arrays and mainly focuses on experimentally validating the methodology. Because the radiation mode–based microphone array can be approximated as a gradient microphone, the difference between them and the advantage of the former over the latter are clarified by comparing the beampatterns. [ABSTRACT FROM AUTHOR]

Background: Tic disorder is a neuropsychiatric disorder characterized by involuntary movements or vocalizations. Previous studies utilizing diffusion-weighted imaging to explore white-matter alterations in tic disorders have reported inconsistent results regarding the affected tracts. We aimed to address this gap by employing a novel tractography technique for more detailed analysis. Methods: We analyzed MRI data from 23 children with tic disorders and 23 healthy controls using TRActs Constrained by UnderLying Anatomy (TRACULA), an advanced automated probabilistic tractography method. We examined fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity, and mean diffusivity in 42 specific significant white matter tracts. Results: Our findings revealed notable differences in the children with tic disorders compared to the control group. Specifically, there was a significant reduction in FA in the parietal part and splenium of the corpus callosum and the left corticospinal tract. Increased RD was observed in the temporal and splenium areas of the corpus callosum, the left corticospinal tract, and the left acoustic radiation. A higher mean diffusivity was also noted in the left middle longitudinal fasciculus. A significant correlation emerged between the severity of motor symptoms, measured by the Yale Global Tic Severity Scale, and FA in the parietal part of the corpus callosum, as well as RD in the left acoustic radiation. Conclusion: These results indicate a pattern of reduced interhemispheric connectivity in the corpus callosum, aligning with previous studies and novel findings in the diffusion indices changes in the left corticospinal tract, left acoustic radiation, and left middle longitudinal fasciculus. Tic disorders might involve structural abnormalities in key white matter tracts, offering new insights into their pathogenesis. [ABSTRACT FROM AUTHOR]

Haptics is a research field related to the sense of touch. When humans perceive vibrations, the magnitude of sensory quantity is determined by the amount of skin displacement. A haptic actuator using mid-air ultrasonic waves is suitable for measuring the skin displacement during tactile presentation because they allow contactless tactile presentation. However, studies that directly observe the amount of skin displacement during the sensing of vibration have been conducted only at a very limited displacement of 3 µm, despite the sensible skin displacement range being approximately 10 mm-0.01 µm. In this study, ultrasonic speakers were used to generate higher sound pressures than conventional ultrasonic speakers to produce large displacements. The goals of this study are to observe the characteristics of skin displacement and to map the amount of displacement to the sensory amount. In this paper, we used a dummy skin instead of a biological skin to investigate the validity of the constructed observation system and the adaptability of the skin viscoelasticity model proposed in the previous study. From the measurement results, obtained at a maximum acoustic radiation pressure of 4000 Pa, a maximum displacement of 170 µm is obtained. This is 50 times larger than that obtained in the previous study. The displacement amount is consistent with the displacement model proposed in the previous study and the elastic modulus obtained from the dynamic viscoelasticity measurement. Furthermore, the simulation results obtained from that model suggest that the displacement characteristics of Asker C15 of HITOHADA® GEL would be similar, suggesting that this HITOHADA® GEL could be used as an alternative material. [ABSTRACT FROM AUTHOR]

The physical characteristics of solid biofuel under combustion in a Rijke tube installation have been studied. A decrease in the flame temperature and an increase in the heat flux density on the tube wall on the occurrence of vibrating combustion were detected. To study vibrating combustion under conditions close to practical use in power plants, experiments were carried out on a "container–tube" type installation. The optimal parameters of the installation for the implementation of vibrating combustion of solid biofuels were obtained. A theoretical model of the development of sound disturbances of a combustion wave has been developed and its influence on heat transfer characteristics has been elucidated. An empirical-theoretical relationship has been obtained for calculating heat transfer in a Rijke tube during vibrating combustion. A model is proposed for calculating the amplitude of disturbances for instabilities in "container–tube" installations. [ABSTRACT FROM AUTHOR]

To study the acoustic radiation characteristics of forced vibration of granular assemblies, the acoustic radiation model of a single particle and the acoustic radiation model of granular assemblies are established. Combined with experimental verification, the variation law of radiated sound power in the process of forced vibration of granular assemblies is studied. The effects of vibration characteristics, material characteristics, mass characteristics, and distance characteristics on the acoustic radiation of forced vibration of granular assemblies are explored. The radiation range of radiated ultrasound in the process of forced vibration of granular assemblies is analyzed. The research results show that under the condition of forced vibration, the radiated sound power of the granular assemblies is obvious. The internal vibration of the granular assemblies will cause the granular particles to radiate the sound power of multiple frequencies outward. The granular particles will produce obvious ultrasonic sound power in the violent vibration state. The frequency of the sound wave will generally have a significant attenuation effect at 10 cm. Considering the relevant experimental research and engineering application of granular materials, the ultrasonic radiation characteristics should be analyzed to avoid the influence of ultrasonic radiation caused by its severe vibration. [ABSTRACT FROM AUTHOR]

Liquid surfaces can be depressed by applying acoustic radiation force. The balance between the acoustic radiation force, surface tension force, and buoyant force sustains the stable dimple depression. Beyond a certain threshold, higher acoustic radiation force leads to instability and bubble formation. The bubble size is determined by the acoustic radiation force and the liquid surface tension. Effective management of bubble generation can be achieved by controlling acoustic radiation waves. A novel method for creating depression on liquid surfaces and generating bubbles is described, which requires neither gas supply nor direct contact with equipment. [ABSTRACT FROM AUTHOR]

In noise-sensitive areas of urban rail transit (URT), sound barriers are often used to block the propagation of on-track noise such as the wheel–rail noise. However, the vibrations induced by passing trains can also transmit to the sound barriers. Therefore, it is necessary to study the acoustic radiation characteristics of the sound barrier under moving train loads and to evaluate whether installing sound barriers will affect the overall low-frequency noise radiation from the elevated railway. In this paper, the train–track–bridge dynamic interaction theory is adopted to establish a dynamics model for train–track–bridge-sound barrier coupled system, and the acoustic theory is employed to establish acoustic boundary element models for sound barrier, box girder bridge and sound barrier-box girder bridge coupled system, respectively. These models are then used to systematically analyze the characteristics and mechanism of vibrational noise of the sound barrier due to passing trains. The effects of sound barrier on the acoustic environment are also evaluated. Finally, the influencing mechanism of sound barrier on low-frequency acoustic radiation of elevated railway is investigated, and suggestions for future research on low-frequency acoustic radiation of elevated railway are presented. The research results show that the sound barrier can become a significant low-frequency sound source during the trains passing. Installing sound barriers on elevated railway affects the sound environment around the railway mainly through acoustic effects on the noise propagation. The installation of sound barriers has an effect on the vibration characteristics of the box girder bridge. In order to explore the characteristics of low-frequency sound radiation of elevated railways installed with sound barriers, it is necessary to reanalyze the acoustic generation mechanism of the entire structure of the bridge-sound barriers coupled system and combine it with the propagation mechanism of various sound sources. [ABSTRACT FROM AUTHOR]

Mechanical bound states in the continuum (BICs) present an alternative avenue for developing high-frequency, high-Q mechanical resonators, distinct from the conventional band structure engineering method. While symmetry-protected mechanical BICs have been realized in phononic crystals, the observation of accidental mechanical BICs—whose existence is independent of mode symmetry and tunable by structural parameters—has remained elusive. This challenge is primarily attributed to the additional radiation channel introduced by the longitudinal component of elastic waves. Here, we employ a coupled wave theory to predict and experimentally demonstrate mechanical accidental BICs within a high-aspect-ratio gallium arsenide phononic crystal grating. We observe the merging process of accidental BICs with symmetry-protected BICs, resulting in reduced acoustic radiation losses compared to isolated BICs. This finding opens up new possibilities for phonon trapping using BIC-based systems, with potential applications in sensing, transduction, and quantum measurements. Mechanical bound states in the continuum (BICs) offer a novel approach for realizing high-frequency, high-Q mechanical resonators. Here, the authors theoretically predict and experimentally demonstrate mechanical accidental BICs in a high-aspect-ratio phononic crystal grating, and their merging with symmetry-protected BICs. [ABSTRACT FROM AUTHOR]

In recent years, underwater wireless ultrasonic energy transmission technology (UWUET) has attracted much attention because it utilizes the propagation characteristics of ultrasound in water. Effectively evaluating the performance of underwater ultrasonic wireless energy transmission is a key issue in engineering design. The current approach to performance evaluation is usually based on the system energy transfer efficiency as the main criterion, but this criterion mainly considers the overall energy conversion efficiency between the transmitting end and the receiving end, without an in-depth analysis of the characteristics of the distribution of the underwater acoustic field and the energy loss that occurs during the propagation of acoustic waves. In addition, existing methods focusing on acoustic field analysis tend to concentrate on a single parameter, ignoring the dynamic distribution of acoustic energy in complex aquatic environments, as well as the effects of changes in the underwater environment on acoustic propagation, such as spatial variability in temperature and salinity. These limitations reduce the usefulness and accuracy of models in complex marine environments, which in turn reduces the efficiency of acoustic energy management and optimization. To solve these problems, this study proposes a method to evaluate the performance of underwater ultrasonic energy radiation based on the spatial distribution characteristics of acoustic power. By establishing an acoustic power distribution model in a complex impedance–density aqueous medium and combining numerical simulation and experimental validation, this paper explores the spatial variation of acoustic power and its impact on the energy transfer efficiency in depth. Using high-resolution spatial distribution data and actual environmental parameters, the method significantly improves the accuracy of the assessment and the adaptability of the model in complex underwater environments. The results show that, compared with the traditional method, this method performs better in terms of the accuracy of the acoustic energy radiation calculation results, and is able to reflect the energy distribution and spatial heterogeneity of the acoustic source more comprehensively, which provides an important theoretical basis and practical guidance for the optimal design and performance enhancement of the underwater ultrasonic wireless energy transmission system. [ABSTRACT FROM AUTHOR]

The vibro-acoustic responses of coupled pump-jet-submarine systems excited by fluid excitations on the wall of the duct are numerically investigated. The unsteady excitations are calculated by computational fluid dynamics and the vibration responses for different excitations on the inner and outer walls are contrastively analyzed through establishing a finite element model of the coupled system. Meanwhile, the effect of fluid–structure interaction and the excitation loading methods for the inner flow of duct are considered. The sound radiation characteristics for different excitation sources are predicted through using a boundary element model. The results show that the excitation force spectra of the inner wall have a remarkable discrete peak at blade passing frequency and its multiple, while the excitation force spectra of the outer wall show a broadband characteristic and discrete components appear at blade passing frequency. The modes of hull both dominate the vibro-acoustic responses of the coupled system for different excitation sources of the duct. The transmitted energy for inner excitation forces is significantly greater than that of outer excitation forces, but the sound radiation efficiency is relatively close. The excitations of the duct can transfer to the thrust bearing through stators as well as the hull and cause a coupled vibration between the duct–stator–hull and the shafting system. Besides, the method for applying distributed forces on the inner wall is more reliable. [ABSTRACT FROM AUTHOR]

Inhomogeneous damping distribution leads to the occurrence of complex modes of structures. Complex modes' vibration and acoustic radiation characteristics are different from real modes. This paper studies the complex modal characteristics of inhomogeneously damped plates for forced vibration. We used the state space method to obtain the complex eigenvalues and eigenvectors of the vibration system and calculated the relationship between modal coordinates and frequency under unit force. The results show that the absolute values of the modal coordinates of two conjugate complex eigenvectors are different, and the structure's vibration is dominated by the eigenvectors corresponding to eigenvalues with positive imaginary parts near natural frequencies. When investigating the structural sound radiation in the vibration mode space, each mode's acoustic radiation is not independent but coupled with each other. The influence of the coupling between complex modes on the calculation results of the acoustic radiation power of the plate is studied in this paper. The results show that the coupling effect between modes cannot be ignored when calculating the acoustic radiation power based on complex modes. Finally, the error of calculating acoustic power using the decoupling approximation instead of the complex mode method is analyzed. [ABSTRACT FROM AUTHOR]

The three-dimensional turbulent mean flow and acoustic field of a supersonic jet impinging on a solid plate is studied computationally using the general purpose CFD code Ansys Fluent. A pressure-based coupled solver formulation with the second order weighted central-upwind spatial discretization is applied to compute transient solutions. Cold and hot jet thermal conditions are considered. Mean flow characteristics are investigated by a steady-state modeling approach. Acoustic radiation of impingement tones is simulated using a transient time-domain formulation. The effects of turbulence in steady-state are modeled by the SST k-ω turbulence model. The Wall-Modeled Large-Eddy Simulation (WMLES) model is applied to compute transient solutions. The near-wall mesh on the impingement plate is fine enough to resolve the viscosity-affected near-wall region all the way to the laminar sublayer. Nozzle-to-plate distance is parameterized in the model for automatic re-generation of the mesh and results. Steady-state predictions of hover lift loss and mean jet velocity distributions are compared with experimental data, and favorable agreement is reported. The transient solution reproduces the mechanism of impingement tone generation by the interaction of large scale vortical structures with the impingement plate. The acoustic near-field is directly resolved by Computational Aeroacoustics (CAA) to accurately propagate impingement tone waves to near-field microphone locations. Calculated impingement tone frequencies and sound pressure levels agree with experimental values. [ABSTRACT FROM AUTHOR]

The analytical expression of the axial acoustic radiation force (ARF) exerted on a spherical particle located on the propagation axis of non-diffracting beams constructed by a discrete superposition of Bessel beams is calculated. The axial acoustic radiation for the fundamental non-diffracting beams as cosine beams, Bessel beams, Mathieu beams, and parabolic or Weber beams are considered. In this study, we extend the recent results on the ARF concerning Bessel and Mathieu beams to include the other fundamental non-diffracting cosine and parabolic beams. Additionally, the influences of each beam parameter, such as the angle of the half cone, the beam's own value, and the beam order on ARF will be examined, and the dependence of ARF with the particle radius is treated. In addition, some numerical simulations are performed the influence these parameters on the ARF. Furthermore, a comparison between the ARF exerted by each non-diffracting beam is accomplished by analyzing the curves of the dimensionless force function Yp versus the size parameter ka. This work may contribute to understanding the interaction between spherical particles and the fundamental non-diffracting beams. [ABSTRACT FROM AUTHOR]

Considering the lack of studies on the transient vibro-acoustic properties of conical shell structures, a Jacobi–Ritz boundary element method for forced vibro-acoustic behaviors of structure is proposed based on the Newmark-β integral method and the Kirchhoff time domain boundary integral equation. Based on the idea of the differential element method and the first-order shear deformation theory (FSDT), the vibro-acoustic model of conical shells is established. The axial and circumferential displacement tolerance functions are expressed using Jacobi polynomials and the Fourier series. The time domain response of the forced vibration of conical shells is calculated based on the Rayleigh–Ritz method and Newmark-β integral method. On this basis, the time domain response of radiated noise is solved based on the Kirchhoff integral equation, and the acoustic radiation characteristics of conical shells from forced vibration are analyzed. Compared with the coupled FEM/BEM method, the numerical results demonstrate the high accuracy and great reliability of this method. Furthermore, the semi-vertex angle, load characteristics, and boundary conditions related to the vibro-acoustic response of conical shells are examined. [ABSTRACT FROM AUTHOR]

The article in the Journal of the Acoustical Society of America discusses integral formulations for predicting acoustic radiation and scattering from finite objects. It highlights the challenges faced by three integral formulations and introduces the combined Helmholtz integral equation formulation (CHIEF) algorithm to address these issues. The CHIEF algorithm is proven to provide unique solutions, making it a significant advancement in numerical computation methods for predicting acoustic radiation. The author, Harry A. Schenck, is credited with this groundbreaking work, which has received over 1000 citations since publication. [Extracted from the article]