Acoustic Behavior Research Articles

Unravelling the dynamics of coated nanobubbles and low frequency ultrasound using the Blake threshold and modified surface tension model.

To develop a model that accurately describes the behavior of nanobubbles (NBs) under low-frequency ultrasound (US) insonation (<250 kHz), addressing the limitations of existing numerical models, such as the Rayleigh-Plesset equation and Blake's Threshold model, in predicting NB behavior.&#xD;Approach. A modified surface tension model, derived from empirical data, was introduced to capture the surface tension behavior of NBs as a function of bubble radius. This model was integrated into the Marmottant framework and combined with the Blake threshold to predict cavitation thresholds at low pressures, providing a comprehensive approach to understanding NB dynamics.&#xD;Main Results. Experimentally, inertial cavitation for NBs with a radius of 85 nm was observed at peak negative pressures (PNP) of 200 kPa at 80 kHz and 1000 kPa at 250 kHz. The Marmottant model significantly overestimated these thresholds (1600 kPa). The modified surface tension model improved predictions at 250 kHz, while combining it with the Blake threshold accurately aligned cavitation thresholds at both frequencies (~150 kPa at low pressures) with experimental results.&#xD;Significance. This work bridges a critical gap in understanding the acoustic behavior of NBs at low US frequencies and offers a new theoretical framework for predicting cavitation thresholds of NBs at low US frequencies, advancing their application in biomedical US technologies.

Influence of Pluronic F68 on Size Stability and Acoustic Behavior of Monodisperse Phospholipid-Coated Microbubbles Produced at Room Temperature.

Ultrasound contrast agents, comprised of phospholipid-coated microbubbles, can be produced as monodisperse populations using a microfluidic flow-focusing device. However, microbubble coalescence remains a significant challenge. High production temperatures (e.g., 55 °C) can be used to suppress coalescence, but it complicates the microfluidic device design and is incompatible with targeting agents and drug conjugates. This study investigates the production of monodisperse microbubbles at room temperature with the addition of the amphiphilic surfactant Pluronic F68. Two 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)-based phospholipid formulations were investigated: F1, containing 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[carbonyl-methoxypolyethylene glycol] (DPPE-PEG5000), and F2, which included both DPPE-PEG5000 and polyoxyethylene(40) stearate (PEG40-stearate). We characterized the size stability and acoustic behavior of monodisperse microbubbles produced with various Pluronic F68 concentrations. Adding 5-10 mol % Pluronic F68 was found to effectively suppress coalescence and facilitated the production of monodisperse microbubbles that remained shelf stable for at least 7 days. Acoustic attenuation measurements revealed a shell stiffness ranging from 0.78 to 0.93 N/m for these microbubbles. The 10 mol % Pluronic F68 addition (10PF) demonstrated superior monodispersity and was selected for further experiments. Upon dilution, the size and resonance frequencies of both F1-10PF and F2-10PF decreased over time, though F2-10PF showed better stability compared to F1-10PF for both metrics. Both F1-10PF and F2-10PF exhibited a stronger subharmonic scattering intensity than SonoVue (clinical approved microbubbles), which offers potential for blood pressure sensing. Our study shows that incorporating Pluronic F68 facilitates the production of monodisperse microbubbles at room temperature that are stable long-term and have excellent acoustical properties, with the F2-10PF formulation demonstrating better stability than the F1-10PF.

Ariasa iporaensis n. sp. (Hemiptera: Cicadidae: Cicadinae: Fidicinini): An Uncommon Brazilian Dry Season Cicada.

The cicada Ariasa iporaensis n. sp. is described. This new species of cicada stands out from others in the Brazilian Cerrado because the adults are present throughout the dry season. Notes on the acoustic behavior, oviposition, exuvia morphology, and emergence patterns are provided. An updated key to the species of Ariasa Distant, 1905 is also provided.

Multispecies comparisons support a startle response origin for a novel vibrational signal in the cricket tribe Lebinthini.

Many animals communicate using call and response signals, but the evolutionary origins of this type of communication are largely unknown. In most cricket species, males sing and females walk or fly to calling males. In the tribe Lebinthini, however, males produce calls that trigger a vibrational reply from females, and males use the substrate vibrations to find the responding female. Here we assess two hypotheses regarding the behavioral origin of this multimodal duet in the Lebinthini. We conducted playback experiments and measured behavioral and neuronal responses in multiple related cricket species to assess whether the precursor to the lebinthine duet was 1) a startle response to high-frequency sound, or 2) elaboration of a preexisting courtship behavior. We found behavioral similarities between the vibrational response of Lebinthini females and the acoustic startle behavior in other gryllid crickets. Specifically, the amplitude of the vibrational reply increases with male song amplitude in Lebinthini, and the magnitude of vibrations produced by two gryllid species when startled with ultrasound also correlates with the stimulus amplitude. Like in-flight startle behavior, the startle vibrations produced by perched crickets are suppressed when low-frequency sound is played simultaneously. We also observed courtship behavior in four gryllid species and found few instances of female vibration. Vibrational signals observed in Gryllus pennsylvanicus females were not correlated with male calls and occurred more frequently in pairs that did not mate after courtship. Combined, accumulating evidence supports the hypothesis that the lebinthine duet more likely evolved from a startle precursor than courtship behavior.

Optimization of the convergent-divergent nozzle tip and reducing the acoustic energy

One of the practical components that can be found in aircraft engines, the Delaval nozzle, works to improve the aircraft's performance in terms of its stability and its capacity to manoeuvre at different speeds of operation. This research concentrates on the acoustic behaviors shown by this nozzle during the transition from low rate to sonic speed. The modification of the nozzle tip at various degrees of inclination on the transition velocity is the procedure used to minimize the amount of acoustic energy emitted. The acoustic behavior is analyzed based on the FW-H acoustics model utilized, and the optimization problem is solved using the practical eddy simulation approach in CFD. The acoustic Power, measured in dB, is estimated at various angles on the nozzle tip, and the performance of the Delaval nozzle is used to show how the redesigned nozzle tip affects the nozzle's acoustic behavior.

Reconfigurable Manipulation of Sound with a Multimaterial 3D Printed Origami Metasurface

AbstractThe challenge in reconfigurable manipulation of sound waves using metasurfaces lies in achieving precise control over acoustic behavior while developing efficient and practical tuning methods for structural configurations. However, most studies on reconfigurable acoustic metasurfaces rely on cumbersome and time‐consuming control systems. These approaches often struggle with fabrication techniques, as conventional methods face limitations such as restricted material choices, challenges in achieving complex geometries, and difficulties in incorporating flexible components. This paper proposes a novel approach for developing a reconfigurable metasurface inspired by the Kresling origami, designed for programmable manipulation of acoustic waves at an operating frequency of 2000 Hz. The origami unit cell is fabricated using multimaterial three‐dimensional (3D) printing technology, allowing for the simultaneous printing of two materials with different mechanical properties, thus creating a bistable origami‐based structure. Through optimization, two equilibrium states achieve a reflection phase difference of π through the application of small axial force, F, or torque, T. Various configurations of the metasurface, generated from different combinations of these two equilibria, enable distinct reflective behaviors with switchable and programmable functionalities. The principle of this work simplifies the shaping of acoustic waves through a straightforward mechanical mechanism, eliminating the need for complex control systems and time‐consuming adjustments.

Thermoacoustic Instability in Combustors

Thermoacoustic instability is a flow instability that arises due to a two-way coupling between acoustic waves and unsteady heat release rate. It can cause damaging, large-amplitude oscillations in the combustors of gas turbines, aeroengines, rocket engines, etc., and the transition to decarbonized fuels is likely to introduce new thermoacoustic instability problems. With a focus on practical thermoacoustic instability problems, especially in gas turbine combustors, this review presents the common types of combustor and burner geometry used. It discusses the relevant flow physics underpinning their acoustic and unsteady flame behaviors, including how these differ across combustor and burner types. Computational tools for predicting thermoacoustic instability can be categorized into direct computational approaches, in which a single flow simulation resolves all of the most important length scales and timescales, and coupled/hybrid approaches, which couple separate computational treatments for the acoustic waves and flame, exploiting the large disparity in length scales associated with these. Examples of successful computational prediction of thermoacoustic instability in realistic combustors are given, along with outlooks for future research in this area.

A review of the Use of Acoustic Organs in Insects in Terms of Predatory Behaviors

Acoustic organs, generally involved in sound generation and hearing, play a crucial role in insects, particularly in communication and mating behaviors. However, although rare, they also contribute to predatory behaviors. Some well-known examples include parasitism in various parasitic flies like Emblemasoma sp., aggressive mimicry in bush crickets (Chlorobalius leucoviridis), which imitate the female cicadas response song, and the use of stridulation by myrmecophilous social parasites like butterflies (Maculinea sp.) and beetles (Paussus sp.) to infiltrate ant nests. Despite the significance of these behaviors, research in this area is limited due to barriers such as lack of facilities and difficulties in collecting samples. Consequently, few studies have been conducted on acoustic behaviors in predatory contexts compared to other major uses like mating. This article will review several general studies on these three aspects, summarizing the methods and findings. The studies indicate that playback experiments and observations play a crucial role, that these behaviors are highly specialized for survival, and that challenges such as limited sample collections remain

Temperature-dependent elastic, mechanical, thermal, and acoustic behavior in alkaline earth semiconductors

Temperature-dependent elastic, mechanical, thermal, and acoustic behavior in alkaline earth semiconductors

A time-domain finite element formulation of the equivalent fluid model for the acoustic wave equation

Sound-absorptive materials such as foam can be described by the equivalent fluid (EF) model. The homogenized fluid’s acoustic behavior is thereby described by complex-valued, frequency-dependent acoustic material parameters. When transforming the acoustic wave equation for the EF model from the frequency domain to the time domain, convolution integrals arise. The auxiliary differential equation (ADE) method is used to circumvent the direct calculation of these convolution integrals. The wave equation and the coupled set of ordinary ADEs are solved in the time domain using the finite element (FE) method. The approach relies on approximating the complex-valued frequency response functions of the inverse equivalent bulk modulus and density by a sum of rational functions consisting of real and complex poles. The order of the rational function approximation defines the number of additionally introduced auxiliary variables per nodal degree of freedom. The presented FE formulation includes a narrow-band non-reflecting boundary condition (NRBC) for normal incidence. The implementation in openCFS shows optimal temporal and spatial convergence for a semi-infinite duct based on the analytic plane wave solution for harmonic excitation. The simulation of a pressure pulse propagating in an infinite EF domain with a scatterer demonstrates the capability for multidimensional, actual transient problems.

Acoustic Emission Behavior and Damage Evaluation of Cement Emulsified Asphalt Mortar under Compression

Acoustic Emission Behavior and Damage Evaluation of Cement Emulsified Asphalt Mortar under Compression

Theoretical modeling and modal analysis of multi-element coupled transducers.

Low-frequency transducers are considerably smaller than the wavelength. When multiple low-frequency transducers are closely packed, they couple with the surrounding water and form a transducer-water-transducer coupling structure called multi-element coupled transducers (MCT). This study presents a theoretical model of the MCT based on radiation and mutual radiation theory and analyzes it under multiple resonance frequencies and vibration modes. The MCT comprising N single-degree-of-freedom elements possesses N resonance frequencies and corresponding vibration modes, and the resonance frequency varies with the spacing between elements. Additionally, the elements have different vibration amplitudes, with the phases of vibration among the elements manifesting as different combinations of in-phase and anti-phase in different vibration modes. Validation is performed through finite element analysis (FEA) and measurements of binary and ternary coupled transducer prototypes. The prototypes comprise bender transducers closely packed in a vertical configuration. The theoretical predictions agree with the FEA and measurement results. Thus, the theoretical model contributes to enhancing the understanding of acoustic transducer behavior in coupled configurations and optimizing the design of low-frequency acoustic arrays.

An analytical method for broadband acoustic analysis of 2D cavities containing or bounded by porous materials

Real-life vibro-acoustic systems often involve porous treatments, resulting in complex-valued and frequency-dependent models that are challenging to solve. Traditional prediction techniques like the finite element (FE) method requires huge computational cost, especially in the mid to high frequency ranges. This paper develops a novel spectral dynamic stiffness (SDS) formulation, using very few number of degrees of freedom but describing the broadband acoustic behaviour of acoustic cavities with porous materials highly accurately. The method employs frequency-dependent shape function that satisfies exactly the (damped) Helmholtz equation to describe the (equivalent) acoustic pressure field, and also features an innovative approach to use the fast-convergent Modified Fourier series to describe any arbitrary acoustic BCs. Finally, the SDS matrices for cavities containing or bounded by porous materials are formulated in an analytical manner. It is demonstrated that the method exhibits a much higher computational efficiency over the FE package COMSOL, at least 6 times faster than the COMSOL with a similar level of accuracy, and benchmark solutions are provided. This promising method can provide a powerful tool for systems with porous materials that have frequency-dependent characteristics, paving the way for efficient and accurate acoustic analysis in complex engineering applications.

Experimental investigation on the effect of concentration on the resonance frequency of lipid coated ultrasonically excited microbubbles

This study presents an experimental investigation of the influence of MB concentration on the resonance frequency of lipid-coated microbubbles (MBs). Expanding on theoretical models and numerical simulations from previous research, this work experimentally investigates the effect of MB size on the rate of resonance frequency increase with concentration, a phenomenon observed across MBs with two different lipid compositions: propylene glycol (PG) and propylene glycol and glycerol (PGG). Employing a custom-designed ultrasound attenuation measurement setup, we measured the frequency-dependent attenuation of MBs, isolating MBs based on size to generate distinct monodisperse sub-populations for analysis. The resonance frequency of MBs was determined by identifying the attenuation peak in the broadband attenuation ultrasound attenuation measurements. Our experimental findings confirm that larger MBs (≈2.1μm) demonstrate a more significant shift in resonance frequency (≈ 5 MHz, ≈ 40%) as a function of MB concentration. In contrast, smaller MBs (≈1.3μm) show a minor shift in the resonant frequency (≈ 1.8MHz, ≈ 8%), underlining the importance of size in determining acoustic behavior compared to changes in the lipid shell properties. Additionally, we observed that resonance frequency increase with concentration reaching a saturation point at higher concentrations. This plateau occurs at higher concentrations for larger MBs (≈2.1μm), while smaller MBs (≈1.6μm and ≈1.3μm) reach this saturation point at lower concentrations. Furthermore, the study highlights the small effect of bubble-bubble interactions on the resonance frequency of MB populations, particularly at lower MB concentrations and for smaller MBs. This insight is important for applications utilizing MB clusters, such as contrast-enhanced ultrasound imaging and MB-mediated therapies. While both size and lipid shell composition influence resonance frequency, MB size has a more significant effect. In conclusion, our findings affirm the need to consider both MB size and concentration when utilizing MBs for clinical and industrial ultrasonic applications.

Analytical and Computational Investigation of VibroThermoAcoustic Behaviour of Cracks in Aerostructures

Abstract This research investigates the Vibro-thermoacoustic dynamics exhibited by Aerostructures, particularly those harbouring surface cracks. Employing a novel approach, a Thermo-Acoustic field coupled Transient Heat Transfer model is developed to model the interplay among vibrations, heat dissipation, and acoustic behaviour at crack tip interfaces. Local surface flaws proximal to stress concentration sites are investigated via the Newmark Beta Method and Finite Element Analysis, which are applied to displacement and thermal mapping at crack tips through temporal and spatial discretization. Recognizing the implications of flaws in structural integrity and potential lifespan reduction, the study incorporates Analytical, Numerical and Computational analysis of surface cracks into the broader context of Thermoacoustic phenomena. &amp;#xD;The paper explores the application of Elastoplastic Fracture Mechanics (EPFM) to model the impact of plastic deformation on crack growth, local acoustic field and the overarching structural integrity of these components. &amp;#xD;In this study, we also investigate the limitations of the original Ramberg-Osgood equation, particularly in its application to modelling nonlinearities in plastic strain at crack tip interfaces. To address these shortcomings, we propose a novel modified Ramberg-Osgood formulation that incorporates Padé Approximants. This modification enables effective modelling of nonlinear stress-strain variations of high-performance materials while improving computational performance and accuracy. &amp;#xD;Real-world aerostructures experience varying loads, and incorporating these principles in our coupled model allows for accurate modelling of Thermoacoustic Field variations and Instability under dynamic conditions. The research offers valuable perspectives for engineering applications, providing a computational roadmap for thermoacoustic modelling in Aerostructures with cracks.

Strain-Dependent Damping of Paulownia Wood at Room Temperature and Constant Moisture Content

"Against the backdrop of global warming and the necessary reduction of CO2, the material wood is experiencing a renaissance as a result of increasing social acceptance. However, questions of harmless reforestation also come to the forefront. Ultimately, plantation cultivation of wood is unavoidable in order to meet the increasing demand for wood in the coming years. Agroforestry is the focus of economic and technical interest in this regard. Paulownia or Kiri tree belongs to the Paulowniaceae family and is the tree with the highest growth rate in the world. It has a large leaf area that can absorb correspondingly high amounts of CO2. Originally from China, it is now planted worldwide and is considered a climate tree. However, it must face the accusation of invasiveness. Therefore, less invasive varieties of Paulownia are of interest. However, these should also have appropriate mechanical properties. One of these material properties is damping, which significantly affects the acoustic behaviour. In this study, the strain-dependent damping was investigated by measuring the logarithmic decrement of free decaying bending oscillations. The measurements were carried out on a common Paulownia species (obtained from plantations in Georgia, Italy and Spain) and a new species of Paulownia obtained from a plantation in Germany. It is worth mentioning that the new wood variety was harvested for the first time in Germany. Since damping is strongly influenced by microstructure, which is in turn influenced by site-specific nutrient supply, this study examined how damping behaviour develops with strain and the extent of its variation. It was found that the damping curves exhibited a strain-independent and a strain-dependent area. The bending modulus was calculated from the oscillation frequency and showed that the values range from about 1024 N/mm2 to 5873 N/mm2 . This large variation appears to stem from the fiber orientation of the tested samples, which also affects the damping values. "

Correlation characteristics of oscillation dynamic and acoustic behavior of a sonoluminescence cavitation bubble

The acoustic cavitation oscillation behavior of a single bubble and the resulting characteristic pressure evolution is a complex dynamic phenomenon. The coupling mechanisms among many characteristic pressures that affect the oscillation characteristics are still ambiguous. A correlation method is applied to analyze the degree of correlation between characteristic pressures and bubble oscillations. The effects of ambient pressure, bubble state, and propagation of driving acoustic pressure on bubble oscillation and size were investigated. The results indicate that the viscosity is the dominant factor affecting bubble oscillating velocity during the growth or collapse processes. The surface tension is strongly correlated with the bubble oscillation, and the oscillating velocity of a bubble greatly suppresses the effect of the viscosity on the bubble oscillation. In particular, the sinusoidal variation in driving acoustic pressure strongly correlates with bubble radius oscillation, and its correlation with bubble acceleration increases linearly. Moreover, two linear relationships between the ambient pressure and the frequency to the characteristic radius are obtained.

Investigating the Acoustic Behavior of Polyurethane Foam Reinforced with Clay Nanoparticles

Introduction: Disturbing noise can cause physical and mental illnesses among workers; for this reason, it is necessary to restrain it, especially in workplaces. Using sound-absorbing materials with suitable acoustic properties has been a growing trend in mitigating noise. This study aimed to improve the acoustic properties of polyurethane foam (PUF) as a sound absorber. Material and Methods: In the present study, PUF was synthesized with different percentages of clay nanoparticles (0 -1.2 wt.%), and then the Sound Absorption Coefficient (SAC) of the synthesized PUF was measured by the acoustic impedance tube in the frequency range of 63 to 6400 Hz according to the ISIRI 9803 standard. The morphology of the foam was also investigated by Scanning Electron Microscope (SEM) Results: The results showed that the addition of clay nanoparticles to PUF improved the sound absorption behavior of the samples, and the best sound absorption behavior was for PUF with 1.2% weight of nanoparticles at low frequencies (500-2600 Hz). This increase in the absorption coefficient can be due to the increase in the number and smaller size of the pores with the increase in the amount of nanoparticles in PUF. Conclusion: This study illustrates that the incorporation of clay nanoparticles into PUF at varying percentages results in an enhanced absorption coefficient. The presence of clay nanoparticles leads to a reduction in cell size and an increase in the number of pores, consequently enhancing surface friction. The absorption coefficient was observed to increase with the growing concentration of clay nanoparticles in PUF.

Enhancement of industrial information systems through AI models to simulate the vibrational and acoustic behavior of machining operations

Advanced simulation tools allow the optimization of processes prior to production implementation. Our study aims to integrate industrial information and data into a digital model based on artificial intelligence (AI) to simulate acoustic and vibration behavior during the production preparation phase. This model integrates real manufacturing conditions with generated vibrations and acoustic waves, creating a comprehensive simulation tool for acoustic and vibration behavior during the production preparation phase. By harnessing Internet of Things (IoT) sensors, Big Data, and Cyber-Physical Systems (CPS), our approach achieves a unified system that consolidates data from diverse sources, facilitating a seamless information flow within an Industry 4.0 framework. Small signal variations made it complex to model manufacturing operations using AI tools, as seen in recent studies. However, the proposed approach overcomes these challenges and has been successfully applied to a numerical lathe using sensors and advanced analytical tools, paving the way for a robust industrial information integration system to optimize and predict operational outcomes.

Sound absorption efficiency of plywood-carbon fiber composites: A new frontier in wood material science

The objective of this study was to investigate the sound absorption efficiency of plywood-carbon fiber composite materials and evaluate their potential as acoustic panels. In this work, plywood and plywood-carbon fiber composite materials were produced using Uludağ fir (Abies nordmanniana subsp. bornmülleriana Mattf.) peeling veneer, woven carbon fiber, and polyvinyl acetate (PVAc) adhesive. Three experimental groups and a control group were created. The materials from plywood-carbon fiber composite were manufactured in three different designs to form experimental groups. The sound absorption coefficients of the plywood and the composite materials were tested via the impedance tube method, according to ASTM standard E1050-98 (2006). Attention was paid to the acoustic behavior at low (bass) frequencies (63 Hz to 250 Hz), mid frequencies (315 Hz to 1600 Hz), and high (treble) frequencies (2000 Hz to 6300 Hz). It was determined that the plywood-carbon fiber composite materials could reflect or transmit sound waves at low (bass) frequencies, while significantly absorbing sound waves at high (treble) frequencies. It can be suggested that plywood-carbon fiber composite materials could be used as sound absorbing acoustic panels.