Acoustic Vibrations Research Articles

Modulating the Acoustic Vibration Performance of Wood by Introducing a Periodic Annular Groove Structure

The acoustic vibration performance of wood affects the quality of many musical instruments, and the variability of wood causes obvious differences between individual timber samples. To mitigate the variations among the individual timber samples intended for musical instruments, in this study, we combined finite element simulation with experimental testing to investigate the effect of the periodic annular groove structure on the comprehensive acoustic vibration characteristics of wood. The results revealed that there are discernible correlations between the structural parameters of the periodic annular groove and the key acoustic parameters of wood, including the resonant frequency, equivalent dynamic modulus of elasticity, equivalent specific dynamic modulus of elasticity, equivalent acoustic radiation quality constant, and equivalent acoustic impedance. These relationships can be used to fine-tune the overall acoustic vibration performance of wood and harmonize the acoustic vibration characteristics among different timber specimens. The effects of the periodic annular groove structure on the five acoustic vibration parameters obtained through finite element simulations exhibited minimal differences to the corresponding results from experimental tests. Furthermore, there was a remarkably strong correlation between the outcomes of the finite element simulations and the experimental test results, with the coefficient of determination exceeding 0.99.

Preliminary study of Acoustic Black Holes implemented in CT/MRI housings including validation experiments

An increasing number of interventional use of computer tomograph (CT) scanners and magnetic resonance tomographs (MRI) leads to the need for particularly quiet medical imaging in order to minimize the stress level for patients as well as medical staff. Due to the many different imaging sequences, noise reduction measures have to consider a wide range of different frequencies. Especially the use of Acoustic Black Holes (ABHs) seems to be a promising strategy to reduce vibration-induced noise. The objective of this study is to extend conventional measures for minimizing structural vibrations, usually realized by applying composite stiffeners, by adding ABHs directly into these stiffening components. This allows vibration maxima to be minimised efficiently. In the first step, the vibroacoustic properties of composite materials are investigated numerically and the created simulation model is validated by experiments. Based on these results, the influence of stiffeners on the structural behaviour is investigated and an optimised design for minimum surface velocities is found. To further reduce surface velocities in the frequency range where the human ear is particularly sensitive, ABHs are tested. In this context it is investigated whether ABHs can be advantageously combined with conventional stiffeners. Keywords: Medical devices, Acoustic black holes, Noise and vibration

Signal Spectrum Analysis of Sediment Water Impact of Hydraulic Turbine Based on ICEEMDAN-Wavelet Threshold Denoising Strategy

Studies show that sediment erosion is one of the main factors attributing to hydraulic turbine failure. The present paper represents an investigation into acoustic vibration signals generated by the water flow impacting the hydraulic turbine runner under three different operating conditions. Collected signals were denoised using the ICEEMDAN-wavelet threshold method, and then the spectral characteristics and sample entropy characteristics of the signals for the three operating conditions were analyzed. The results show that when clean water flows through the hydraulic turbine, the sample entropy reaches its smallest values and the dominant frequency component in the spectrogram is 59.39 Hz. When transitioning from clean water to the flood flow containing 2–4 mm sediment particles, the sample entropy is increasing and a high-frequency component higher than 59.39 Hz becomes the prominent frequency of the spectrogram. Meanwhile, the formation of high-frequency components increases with the sand-containing particle size. Based on the spectral characteristics and sample entropy characteristics of the acoustic vibration signals under different operating conditions, it can provide a reference for the sand avoidance operation of the hydraulic turbine during flood season. In addition, it provides a supplement to the existing hydraulic turbine condition’s monitoring systems and a new avenue for subsequent research on early warning of hydraulic turbine failure.

The first distributed-mass high-performance programmable optoelectromechanical steerable motion-wave sensors focused on sophisticated biomedical applications

This paper introduces the first high-performance distributed-mass acoustic sensor made of cascaded differential phase shift suspended slot waveguide sections in a Mach–Zehnder interferometer optical transducer circuit. The heavyweight seismic mass used in traditional optoelectromechanical sensors is replaced by an fg lightweight coupling arm yielding an extra compact fast responding structure enabling utilizing over 64\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$64$$\\end{document} cascaded sections and resulting in enhancing the performance by hundreds of times. The transducer operation relies on converting the acoustic vibration into phase modulation of the light for a splendid performance. The novel sensor architecture challenges achieving optical sensitivities higher than 33×103%/g\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$33\ imes {10}^{3} \\%/\\mathrm{g}$$\\end{document} (33 times supersensitive), operating at ultrasonic acoustic speeds higher than 27 MHz, and recognizing resolutions in the 1 ng order. The programmable sensor is voltage-controlled supporting the operation in multimodes. Four operation modes are elucidated including the natural aspiration force, turbo electrostatic force open-loop voltage control, zero-force closed-loop voltage control, and dynamic turbo-force closed-loop voltage control. Wide dynamic ranges for controlling the optical sensitivity and maximum measurable acceleration up to 115.5 dB are reported. Steering capabilities of the acoustic beam in the azimuth plane are demonstrated utilizing two-spoke and three-spoke directional architectures supporting 116.64∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$116.64^\\circ$$\\end{document} and 360∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$360^\\circ$$\\end{document} of respective steering angles. Potential acoustic biosignal-based applications in the medical field are outlined.

Efficient denoising of cold atom images using the optimized eigenface recognition algorithm.

Absorption imaging is a widely employed technique for detecting cold atom clouds and Bose-Einstein condensates (BECs). There are situations where such images may suffer from unwanted interference fringes, resulting in uncertainties in determining crucial parameters such as the atom number, temperatures, or even dynamics in small timescales. Reducing the acoustic vibrations and recording image frames synchronized with the source of such vibrations can largely reduce these fringes; however, some residual fringes still need to be taken care of for precision measurements. In this study, we propose an efficient image post-processing technique for noise reduction that effectively mitigates such interference patterns. Our approach makes use of the well-known eigenface recognition algorithm, combined with an optimized masking strategy applied to the image of the atomic cloud using a small number of basis sets. The use of a limited basis set ensures minimal computational time, allowing this method to be readily incorporated into every experimental run. Through the application of our technique, we successfully reduce interference fringes and improve the accuracy of parameter estimation by 50% in the absorption imaging of cold atoms. The temperature uncertainties of cold 87 R b atoms are reduced by more than 50% after the algorithm is applied. This approach holds significant promise for enhancing the reliability and precision of experimental measurements in diverse research fields where absorption imaging is employed.

Radiative heat exchange driven by acoustic vibration modes between two solids at the atomic scale

Radiative heat exchange driven by acoustic vibration modes between two solids at the atomic scale

Noise Source Diagnosis Method Based on Transfer Path Analysis and Neural Network

Clarifying the noise source and the contribution of each path is essential for the system’s noise control. The auxiliary converter cabinet, which is a crucial component of rail transportation, has numerous intricate noise sources. The contribution of each path point must be inverted-solved using known transfer functions and target point test values when identifying noise sources. This article suggests a method for diagnosing noise using transfer path analysis and neural networks (TPA-NN). Firstly, the principle and scheme for analyzing the transmission path of the converter cabinet are proposed. The transfer function of each path is obtained by selecting suitable path points, reference points, and target points for air and structure acoustic vibration experiments. The external target point data are then combined with the neural network’s linear fitting function, and the contribution of each path is used as an output for network training while some path point contributions are rebuilt. The results indicate that the method’s outcomes are most accurate when the converter cabinet’s path point is 13 and the target point is 6. This approach offers an innovative technique for locating noise sources in intricate systems.

The Modeling of Disc-shaped Acoustic Black Hole Plate and Vibration Characteristics

The Acoustic Black Hole (ABH) structure has great potential in vibration and noise control due to the characteristics of high damping and energy accumulation. A dish-shaped two-dimensional acoustic black hole plate is proposed in order to reduce the possibility of the structural damage happened in conventional embedded ABH in the centre of the plate. The dish-shaped acoustic black hole plate only cuts ABH on the edge. The finite element method is often used to establish the model of acoustic black hole plates. However, it is high cost and low efficiency in computation. A semi-analytical theoretical model of the disc-shaped acoustic black hole plate based on Gaussian expansion method is established in order to improve computation efficiency. Meanwhile, the shape function filtering method is proposed to solve the problem of non-convergence when Gaussian expansion method is used to model a non-rectangular plate. A finite element model of the disc-shaped acoustic black hole plate is established and used to verify the accuracy of the proposed semi-analytical theoretical model. The results show that the dish-shaped acoustic black hole plate has excellent energy accumulation effect and can be used further as Dynamic Vibration Absorber (DVA) to reduce the vibration of host structure.

A unified hybrid Ritz-SEA acoustic vibration coupling method of a rectangular plate coupled with fast multipole boundary integration

The Ritz method, based on a segmental strategy, is known for its fast convergence and ability to handle arbitrary boundary conditions while maintaining accuracy comparable to benchmark solutions. It is particularly effective in calculating vibrations in composite laminates, functionally graded plates, and other novel plate types. However, this method faces challenges in accurately calculating the mid-frequency problems that arise between plate structures and acoustic cavities. To fill this gap, this paper proposes a Ritz and statistical energy analysis (Ritz-SEA) hybrid method for calculating rectangular plate acoustic vibration coupling in the mid-frequency range for both deterministic and random loads. This method utilizes the fast multi-pole boundary element integral equation and region segmentation mapping as the governing equation for the coupling boundaries. The power flow equation of the statistical energy analysis (SEA) method is incorporated to solve for the average sound pressure level and sound power level of the coupled acoustic cavity. A method that combines the CHIEF and Burton-Miller methods has been proposed to address the issue of non-unique solutions. Validation and parametric studies are conducted. The results demonstrate that this approach can effectively filter out random fluctuations in mid-frequency domains while exhibiting exceptional stability and precision.

Monitoring acoustic vibrations in optical fibers by estimating polarization matrix variation with the integration of coherent optical communication and sensing.

In this paper, we propose a novel architecture called as the Direct-Computation-Sensing Architecture (DCSA) to directly calculates the polarization state changes caused by optical fiber vibrations with training data, offering a more accurate and responsive method than that with adaptive filter-based sensing architectures. We detected the distinct fiber vibration induced by piezoelectric ceramics in an established experimental platform, and recovered a song melody played near the optical fiber buddle from the fiber's polarization changes. We locate the source of the vibration by comparing data from both ends of a bidirectional transmission setup. Lastly, we conducted field tests under conditions involving machine-induced vibrations and natural cable movements.

Sensitivity of Localized Surface Plasmon Resonance and Acoustic Vibrations to Edge Rounding in Silver Nanocubes.

Precise knowledge of the dependence of nano-object properties on their structural characteristics such as their size, shape, composition, or crystallinity, in turn, enables them to be finely characterized using appropriate techniques. Spectrophotometry and inelastic light scattering spectroscopy are noninvasive techniques that are proving highly robust and efficient for characterizing the optical response and vibrational properties of metal nano-objects. Here, we investigate the optical and vibrational properties of monodomain silver nanocubes synthesized by the chemical route, with edge length ranging from around 20 to 58 nm. The synthesized nanocrystals are not perfectly cubic and exhibit rounded edges and corners. This rounding was quantitatively taken into account by assimilating the shape of the nanocubes to superellipsoids. The effect of rounding on their optical response was clearly evidenced by localized surface plasmon resonance spectroscopy and supported by calculations based on the discrete dipole approximation method. The study of their acoustic vibrations by high-resolution low-frequency Raman scattering revealed a substructure of the T2g band, which was analyzed as a function of rounding. The measured frequencies are consistent with the existence of an anticrossing pattern of the two T2g branches. Such an avoided crossing in the T2g modes is clearly evidenced by calculating the vibrational frequencies of silver nanocubes using the Rayleigh-Ritz variational method that accounts for both their real size, shape, and cubic elasticity. These results show that it is possible to assess the rounding of nanocubes, including by means of ensemble spectroscopic measurements on well-calibrated particles.

Flow pattern and power consumption of mixing highly viscous fluids under vertical acoustic vibration

This study analyzes the flow pattern and power consumption of mixing highly viscous fluids under vertical acoustic vibration, and investigates the effects of various process parameters on them. A numerical simulation of solid-liquid-gas multiphase flow has been created based on the Volume of Fluid (VOF) model and Discrete Phase Model (DPM), which has been verified through experimentation. When subjected to acoustic vibration, the fluids within the vessel and the wall interact dynamically, driven by a mixing force comprised of both pressure and viscous forces. Notably, the degree to which the fluids absorb mixing power is highly dependent on the mixing force itself, the vessel's velocity, as well as the phase difference between them. Throughout the mixing process, the amplitudes of the instantaneous mixing power and mixing force gradually diminish. Nevertheless, the effective mixing power indeed increases due to the phase effect. Increasing the frequency or amplitude of vibration can expedite the mixing process, leading to improved mixing uniformity and significantly enhancing the effective mixing power. However, the energy absorbed by the fluids is highly nonlinear with respect to the frequency or amplitude of vibration. Achieving higher mixing efficiency can be attained by selecting suitable vibration parameters without increasing power consumption.

Resonant Excitation of Acoustic Vibrations of Spherical Thin Films by Electromagnetic Waves

Resonant Excitation of Acoustic Vibrations of Spherical Thin Films by Electromagnetic Waves

Resonant excitation of acoustic vibrations spherical thin films by electromagnetic waves.

The possibility of excitation of acoustic vibrations of a spherical thin film by electromagnetic waves is considered. A comparison of the numerical and analytical solutions is given. The concept of spatial resonance is introduced. It has been shown that not only frequency is important, but also wavelength. The results obtained can be used to measure parameters of various environments and for medical purposes.

Apple Firmness Prediction During Shelf Life Using the Finite Element Method and Acoustic Vibration Response

Apple Firmness Prediction During Shelf Life Using the Finite Element Method and Acoustic Vibration Response

A Linesearch-Based Algorithm for Topology and Generative Optimization of Switched Reluctance Machines

The switched reluctance machine is considered as the simplest machine in terms of the machine structure. The lack of permanent magnets on the rotating part enables the machine to operate at high speeds and reduces the thermal requirements of the machine. However, the double salient structure of the SRMs creates challenges such as high acoustic noise, vibrations and high machine torque ripples. Topology optimization is used in the literature to enhance the dynamic performance of the switched reluctance machines. This paper introduces a new ON/OFF optimization method based on the line search method to overcome the limitations of the conventional annealing-based ON/OFF optimization. The proposed method shows a faster convergence to optimal solutions than the conventional annealing-based ON/OFF method. The paper also compares the performance of the generative optimization and the topology optimization of a 6/14 switched reluctance machine with the proposed method and the conventional method. The two methods are applied to two different design domains of the machine for topology and generative optimization and the results are compared to the results of the annealing-based ON/OFF method. The results show the effectiveness of the newly proposed method.

Transformer winding mechanical fault diagnosis method based on closing transient acoustic vibration signal

The current conventional transformer winding fault diagnosis method mainly extracts the vibration signal through the time-frequency analysis method, which leads to poor diagnosis due to the lack of analysis of the transformer winding state. In this regard, a transformer winding mechanical fault diagnosis method based on the closing transient acoustic vibration signal is proposed. The closing vibration signals of the transformer in the normal and loose winding states are collected separately, the transformer winding force situation is analysed, and the transformer fault signal characteristics are extracted and combined with a fault classifier to construct a fault diagnosis model. In the experiments, the proposed method is verified for fault identification. The experimental results show that the proposed method has a high correct rate when used to identify different types of transformer faults, and has a more desirable fault diagnosis performance.

METHODOLOGICAL ASPECTS OF INTERSPECIES EXTRAPOLATION OF EXPERIMENTAL DATA UNDER PULSED ACOUSTIC INFLUENCE ON BIOOBJECTS (REVIEW)

Background. Despite a significant number of theoretical and experimental studies, the issue of determining the threshold levels of pulsed acoustic exposure, when exceeded, their negative effect on the morphofunctional state of a biological object begins to appear. Traditionally, in laboratory conditions, such estimates are obtained in experiments on animals, varying the parameters of exposure, followed by extrapolation of the results obtained to humans. However, the pathophysiological mechanisms of disturbances that develop in experimental animals as a result of impulse acoustic impacts have not been sufficiently studied in this context, and indicators of the state of the physiological systems of a biological object that are sensitive to acoustic impulses are not currently taken into account when determining their safe levels.
 Purpose. The purpose of the work was to analyze the pathophysiological mechanisms of the development of biological effects of pulsed low-intensity acoustic exposure at different levels of the organization of a living system and to develop a methodological approach to obtaining a quantitative assessment and extrapolation of data on such exposure from animals to humans, taking into account the physical parameters of the acoustic factor and characteristics of the state of the experimental biological object.
 Materials and methods. The selection and systematic review of the scientific literature on the topic of research by keywords in specialized bibliographic databases was carried out.
 Results. The analysis and generalization of the existing theories about the pathophysiological mechanisms of the biological action of acoustic impulses at different levels of the organization of a living system have been carried out. An original hypothetical scheme for interpreting the effects of acoustic exposure in animals is proposed, which is suitable for obtaining threshold estimates of the levels of the adverse effect of the factor on clinical parameters in experimental animals, and vulnerable critical links in the regulation of external respiration in mammals that cause the damaging effect of acoustic vibrations are identified. A scientific and methodological approach to interspecies extrapolation of medical and biological effects of exposure to low-amplitude air pressure waves from animals to humans has been developed, taking into account the anatomical and physiological parameters of the respiratory system of experimental animals, as well as the informative characteristics of the acoustic pulse. An empirical model is proposed that makes it possible to predict the threshold levels of the conditional power of adverse acoustic effects in humans using data on the development of lung damage in experimental animals of various biological species, and the features of setting up such a model are formulated.
 Conclusion. It has been substantiated that it is relevant to refine the proposed empirical model and develop a theoretical model for extrapolation of the initial experimental data on the threshold of safe acoustic exposure from animals to humans, taking into account the interspecific patterns of functioning of physiological systems of the body that are critical to the impact.

Coexistence of Zero-Dimensional Electride State and Superconductivity in AlH2 Monolayer

Electrides, which confine “excess anionic electrons” in subnanometer-sized cavities of a lattice, are exotic ionic crystals. We propose a non-stoichiometric strategy to realize intrinsic two-dimensional (2D) superconducting electride. AlH2 monolayer, which is structurally identical to 1H-MoS2, possesses zero-dimensionally confined anionic electrons in the interstitial sites of Al triangles, corresponding to a chemical formula of [AlH2]+e−. The interaction between interstitial anionic electrons (IAEs) and host cation lattice mainly accounts for stabilization of 1H-AlH2 electride. Impressively, 1H-AlH2 monolayer is an intrinsic Bardeen–Cooper–Schrieffer superconductor with T c = 38 K, which is the direct consequence of strong coupling of the H-dominated high electronic states with Al acoustic branch vibrations and mid-frequency H-derived phonon softening modes caused by Kohn anomalies. Under tensile strain, IAEs transform into itinerant electrons, favoring the formation of stable Cooper pairs. Therefore, T c reaches up to 53 K at a biaxial fracture strain of 5%. Our findings provide valuable insights into the correlation between non-stoichiometric electrides and superconducting microscopic mechanisms at the 2D limit.

Analysis of the Room Acoustic with Impedance Boundary Conditions in the Full Range of Acoustic Frequencies

An efficiency of the nonsingular meshless method (MLM) was analyzed in an acoustic indoor problem. The solution was assumed in the form of the series of radial bases functions (RBFs). Three representative kinds of RBF were chosen: the Hardy’s multiquadratic, inverse multiquadratic, Duchon’s functions. The room acoustic field with uniform, impedance walls was considered. To achieve the goal, relationships among physical parameters of the problem and parameters of the approximate solution were first found. Physical parameters constitute the sound absorption coefficient of the boundary and the frequency of acoustic vibrations. In turn, parameters of the solution are the kind of RBFs, the number of elements in the series of the solution and the number and distribution of influence points. Next, it was shown that the approximate acoustic field can be calculated using MLM with a priori error assumed. All approximate results, averaged over representative rectangular section of the room, were calculated and then compared to the corresponding accurate results. This way, it was proved that the MLM, based on RBFs, is efficient method in description of acoustic boundary problems with impedance boundary conditions and in all acoustic frequencies.