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Underwater pulsed spark discharge has been widely used in industrial fields as a source of shock waves or acoustic waves, and numerical modeling of the discharge and pressure wave characteristics is necessary to improve the application performance. In this paper, a numerical model is proposed that couples the circuit equation, the mass and energy conservation equations, and a momentum conservation equation based on the Rankine–Hugoniot conditions. A tabulated wide range equation of state and conductivity data of water are used, and various physical processes during the plasma channel expansion are considered, including the energy flow and mass exchange between the channel and the surrounding water due to thermal radiation, evaporation, and condensation. The model self-consistently solves the circuit current and voltage, the plasma channel parameters including composition, temperature, conductivity, pressure, etc., and the pressure profile at a certain distance from the discharge channel. The calculated results show good consistency with the experimental measurements, and three sets of experimental results from other literature are tested to further verify the applicability and effectiveness of the model. [ABSTRACT FROM AUTHOR]

Acoustic holography (AH) provides a promising technique for arbitrary acoustic field reconstruction, supporting many applications like robotic micro-nano manipulation, neuromodulation, volumetric imaging, and virtual reality. In AH, three-dimensional (3D) acoustic fields quantified with complex-valued acoustic pressures are reconstructed by virtue of two-dimensional (2D) acoustic holograms. Phase-only hologram (POH) is recently regarded as an energy-efficient way for AH, which is typically implemented by a dynamically programmable phased array of transducers (PATs). As a result, spatiotemporal precise acoustic field reconstruction is enabled by precise, dynamic, and individual actuation of PAT. Thus, 2D POH is required per arbitrary acoustic fields, which can be viewed as a physical inverse problem. However, solving the aforementioned physical inverse problem in numerical manners poses challenges due to its non-linear, high-dimensional, and complex coupling natures. The existing iterative algorithms like the iterative angular spectrum approach (IASA) and iterative backpropagation (IB) still suffer from speed-accuracy trade-offs. Hence, this paper explores a novel physics-iterative-reinforced deep learning method, in which frequency-argument contrastive learning is proposed facilitated by the inherent physical nature of AH, and the energy conservation law is under consideration. The experimental results demonstrate the effectiveness of the proposed method for acoustic field reconstruction, highlighting its significant potential in the domain of acoustics, and pushing forward the combination of physics into deep learning. [ABSTRACT FROM AUTHOR]

The body–boundary correspondence refers to the relationship between the body and boundary states of topological insulators (TIs). In TIs, the presence of boundary states is connected to the bulk topological properties of the material. The topology can be identified by studying the energy of the topological modes within the bulk bandgap. However, not all topological materials exhibit boundary states within the insulating energy gap. In many cases, the presence of boundary states can be hidden or masked by the bulk energy bands, making it difficult to measure TIs. Recent experiments have shown that defects, which are commonly found in crystalline materials, can be used as probes to explore higher-order topologies that have been recently realized on various platforms. These defects can generate fractional charges and stable bound states in the dispersion region, allowing us to observe the clear body–disclination correspondence. We have performed simulations using a coupled acoustic cavity system with C3 and C5 symmetries to investigate the body–disclination correspondence in topological crystal insulators (TCIs) in the field of acoustics. Simulation and theoretical results have demonstrated that defects such as disclinations can be used to probe higher-order topologies that were previously unobservable in three-dimensional structures. This approach allows us to detect fractional mode charges and stable bound states, which are crucial for understanding the topological nature of TCIs. Our work demonstrates the potential of using disclination defects to study the intricate relationship between the body and boundary states in topological materials, particularly in the context of acoustics. [ABSTRACT FROM AUTHOR]

The application of terahertz radiation has been shown to affect both protein structure and cellular function. As the key to such structural changes lies in the dynamic response of a protein, we focus on the susceptibility of the protein's internal dynamics to mechanical stress induced by acoustic pressure waves. We use the open-boundary molecular dynamics method, which allows us to simulate the protein exposed to acoustic waves. By analyzing the dynamic fluctuations of the protein subunits, we demonstrate that the protein is highly susceptible to acoustic waves with frequencies corresponding to those of the internal protein vibrations. This is confirmed by changes in the compactness of the protein structure. As the amplitude of the pressure wave increases, even larger deviations from average positions and larger changes in protein compactness are observed. Furthermore, performing the mode-projection analysis, we show that the breathing-like character of collective modes is enhanced at frequencies corresponding to those used to excite the protein. [ABSTRACT FROM AUTHOR]

We employed high-pressure Brillouin scattering to study the pressure dependencies of acoustic modes of glycerol up to 14 GPa at 300 K. We observed longitudinal acoustic velocities and transverse acoustic velocities for the first time from 5 to 14 GPa. The results allow the determination of a complete set of elastic properties and an accurate determination of the pressure–volume (P–V) equation of state (EOS). EOS parameters, K0 = 14.9 ± 1.8 GPa and K′0 = 5.6 ± 0.5, were determined from fits to the data from ambient pressure to 14 GPa. Direct volume measurements of the P–V EOS are consistent with those determined by Brillouin scattering. A deviation from a Cauchy-like relationship for elastic properties was observed, and the pressure dependencies of the photoelastic constants and relaxation times were documented from 5 to 14 GPa. These results have broad implications for glass-forming liquids, viscoelastic theory, and mode coupling theory. [ABSTRACT FROM AUTHOR]

In this context, we report the acoustic shock wave processing on amorphous Carbon quantum dots (a-CQD) such that its degree of graphitization and magnetic properties are analyzed. Analytical techniques such as the Raman spectrometer, high resonation–transmission electron microscopy (HR-TEM) and vibrating sample magnetometer (VSM) are utilized to understand the structural, morphological and magnetic properties changes under shocked conditions. The Raman spectroscopic data reveal that the I D /I G ratio is slightly reduced under shocked conditions and the observed values are 0.78, 0.77 and 0.75 for the respective 0, 150 and 300 shocked conditions. The formation of ultra-short-range graphitic nanostructures is confirmed by HR-TEM results at the 300-shocked condition. The most convincing and supporting results for the enhancement of the degree of graphitization are found by the outcome of the magnetic properties such that the saturation magnetization (Ms) is found to be linearly reduced with respect to the number of shock pulses and the observed values are 0.869, 0.757 and 0.710 emu/g for the 0, 150 and 300 shocked conditions, respectively. The electrical resistance of the a-CQD is found to be linearly reduced with respect to the number of shock pulses due to the reduction of sp3 carbon networks. The formation of crystalline graphitic nanostructures in amorphous CQD is explained on the basis of the hot-spot nucleation mechanism. Based on the obtained Raman, HR-TEM and VSM results, during the shocked conditions, slight enhancement of the graphitization is observed; however, from the structural stability point of view, the Carbon dots have high shock resistance than that of the amorphous carbon nanoparticles, multi-wall carbon nanotubes, and reduced graphene oxide nanoparticles. Hence, the title quantum dots can be strongly considered for the applications of device fabrication. [ABSTRACT FROM AUTHOR]

• Tube arrangement of electronic expansion valves affects throttling noise. • Large inclination angle of inlet tube is beneficial to reduce throttling noise. • Refrigerant flowing into an expansion valve should be vertical to the needle. The two-phase throttling noise in electronic expansion valves (EEVs) of a multi-split air conditioner may exhibit different intensities due to the variable EEV tube arrangements. The purpose of this study is to experimentally investigate the influence of EEV tube arrangement on the throttling noise, and to find a suitable tube arrangement for noise reduction. A throttling noise testing rig is constructed to investigate the influence of tube arrangement including the inclination angle of inlet tube and the refrigerant flow direction. The test conditions for tube arrangement include an inlet tube inclination angle of 0°–90° as well as the flow direction from tube P (parallel to the valve needle direction) to tube V (vertical to the valve needle direction) and from tube V to tube P ; and the test conditions for refrigerant include a mass flow rate of 30–90 kg h−1 and an inlet quality of 0.02–0.4. The experimental results show that, the increase of inlet tube inclination angle may weaken the throttling noise, and the sound pressure level (SPL) of throttling noise is decreased by 20.1 % as the inlet tube inclination angle increases from 0° to 90°; and the refrigerant flow direction from V – P (tube V to tube P) instead of P – V (tube P to tube V) may attenuate the throttling noise. The tube arrangement with inlet tube inclination angle of 90° and flow direction from V – P is suggested for minimizing the throttling noise in multi-split air conditioners. [ABSTRACT FROM AUTHOR]

• Electromechanical governing equations of Helmholtz Resonator-type Flexoelectric Acoustic Energy Harvester is derived. • Multiscale method is employed to obtain the amplitude-frequency curve and voltage output response of the harvester. • An expression for the optimized structural parameters of the acoustic energy harvester is provided. • The maximum output voltage is increased by 39.1 % compared to the non-optimized acoustic energy harvester. This paper presents a Helmholtz Resonator-type Flexoelectric Acoustic Energy Harvester (HR-FAEH), composed of a Helmholtz Resonator (HR) and a double-sided Flexoelectric Disk Oscillator (FDO). The electromechanical governing equations, incorporating geometric nonlinearity, are derived using Hamilton's principle. Utilizing the multiscale method, we obtain the cavity sound pressure, oscillator displacement, and voltage output response, with validation through simulations in COMSOL. The study's innovation lies in the concurrent consideration of piezoelectric and flexoelectric effects, enhancing the system's performance. The inclusion of geometric nonlinearity, accounting for large deformations, enhances the model's accuracy under high sound pressure excitations. Our research unveils performance degradation in the Helmholtz Resonator-type acoustic energy harvester under elevated environmental sound pressure. The combination of nonlinear analysis and structural optimization effectively mitigates this degradation. In comparison to the non-optimized harvester, the maximum voltage output increases by 39.1 %, and expressions for the optimized model parameters are provided. Additionally, we conduct parameter analyses for the HR and the FDO, elucidating the impact and optimal values of parameters such as film coverage radius and load resistance on system performance. [ABSTRACT FROM AUTHOR]

The standard configuration of a sonic black hole (SBH) is a discrete set of rings with back cavities at a duct termination, whose inner radii decrease according to a power-law. Although several practical realizations of this type of slow-sound waveguide have been investigated, the continuous problem in which the number of ring/cavity sets goes to infinity has not been analyzed in depth. Understanding its performance is interesting in itself and could provide clues for new designs. For this purpose, we transform the generalized Webster equation for the acoustic pressure inside the ideal SBH into a spatially varying wavenumber Helmholtz equation for a new locally scaled pressure. We eliminate the singularity of the original problem at the SBH termination by considering a rigid residual surface that will be shown to play a role analogous to that of the acoustic black hole (ABH) residual thickness in beams and plates. The variational formulation of the Helmholtz equation is presented and solved by expanding the unknown scaled pressure in terms of a basis of Gaussian functions. The same framework is used to set up an eigenvalue problem that provides the SBH modes and thereby a modal decomposition for the pressure within the SBH. Once the theoretical foundations are established, the variation of the speed of sound and wavenumber in the SBH is presented. The dependence of the shape and distribution of the modes on the residual surface and damping helps to clarify the occurrence and disappearance of oscillations in the input admittance and reflection coefficient of the SBH at different frequencies. For the latter, a detailed parametric study is carried out. Alternative profiles to the power law are also investigated, some showing reflection coefficient values similar to those of the classical SBH. • Sonic black holes at the end of ducts provide minimal wave reflection. • A theoretical approach is proposed to solve the SBH governing equation. • The modal distribution in the SBH is strongly affected by the residual radius. • The modal distribution explains the oscillations in the reflection coefficient. • Alternative SBH profiles to the power law are studied. [ABSTRACT FROM AUTHOR]

The acoustic emission (AE) method is a nondestructive test method used when monitoring the damage propagation by detecting high-frequency elastic waves produced by the refraction process. Self-compacting concrete (SCC) is a special type of concrete that does not require vibration, has excellent fluidity, and is resistant to segregation. In this study, it is aimed to investigate the functioning of the AE technique, which is frequently used in normal concrete, in the behavior of SCC. For this purpose, simultaneous monitoring of SCCs under uniaxial compression load was performed with the AE method. In the concrete production, CEM I 42.5 R cement was used as binder, and fly ash (FA) and marble powder (MP) were used as mineral additives. The mineral additives used in the mixture were replaced with cement at a rate of 20%. In addition to the compressive strength of SCCs, crack analysis, AE amplitude, AE energy, ringing counts, and cumulative count results were investigated as a result of AE measurements. With the AE parameters obtained as a result of the simultaneous measurement, the behavior of SCCs under uniaxial load was successfully monitored. It has been observed that the behavior of SCC using different mineral additives changes according to the mineral additive type. Although the differences in compressive strengths are small, it has been demonstrated that the AE method can be followed successfully in different concrete types and different contents and the behavioral differences are revealed. [ABSTRACT FROM AUTHOR]

This paper presents an acoustic transducer for fully implantable cochlear implants (FICIs), which can be implanted on the hearing chain to detect and filter the ambient sound in eight frequency bands between 250 and 6000 Hz. The transducer dimensions are conventional surgery compatible. The structure is formed with 3 × 3 × 0.36 mm active space for each layer and 5.2 mg total active mass excluding packaging. Characterization of the transducer is carried on an artificial membrane whose vibration characteristic is similar to the umbo vibration. On the artificial membrane, piezoelectric transducer generates up to 320.3 mVpp under 100 dB sound pressure level (SPL) excitation and covers the audible acoustic frequency. The measured signal‐to‐noise‐ratio (SNR) of the channels is up to 84.2 dB. Sound quality of the transducer for fully implantable cochlear implant application is graded with an objective qualification method (PESQ) for the first time in the literature to the best of the knowledge, and scored 3.42/4.5. [ABSTRACT FROM AUTHOR]

Key Points: Questions: Do US government officials and their family members involved in anomalous health incidents (AHIs) differ from control participants with respect to clinical, biomarker, and research assessments? Findings: In this exploratory study that included 86 participants reporting AHIs and 30 vocationally matched control participants, there were no significant differences in most tests of auditory, vestibular, cognitive, visual function, or blood biomarkers between the groups. Participants with AHIs performed significantly worse on self-reported and objective measures of balance, and had significantly increased symptoms of fatigue, posttraumatic stress disorder, and depression compared with the control participants; 24 participants (28%) with AHIs presented with functional neurological disorders. Meaning: In this exploratory study, there were no significant differences between individuals reporting AHIs and matched control participants with respect to most clinical, research, and biomarker measures, except for self-reported and objective measures of imbalance; symptoms of fatigue, posttraumatic stress, and depression; and the development of functional neurological disorders in some. Importance: Since 2015, US government and related personnel have reported dizziness, pain, visual problems, and cognitive dysfunction after experiencing intrusive sounds and head pressure. The US government has labeled these anomalous health incidents (AHIs). Objective: To assess whether participants with AHIs differ significantly from US government control participants with respect to clinical, research, and biomarker assessments. Design, Setting, and Participants: Exploratory study conducted between June 2018 and July 2022 at the National Institutes of Health Clinical Center, involving 86 US government staff and family members with AHIs from Cuba, Austria, China, and other locations as well as 30 US government control participants. Exposures: AHIs. Main Outcomes and Measures: Participants were assessed with extensive clinical, auditory, vestibular, balance, visual, neuropsychological, and blood biomarkers (glial fibrillary acidic protein and neurofilament light) testing. The patients were analyzed based on the risk characteristics of the AHI identifying concerning cases as well as geographic location. Results: Eighty-six participants with AHIs (42 women and 44 men; mean [SD] age, 42.1 [9.1] years) and 30 vocationally matched government control participants (11 women and 19 men; mean [SD] age, 43.8 [10.1] years) were included in the analyses. Participants with AHIs were evaluated a median of 76 days (IQR, 30-537) from the most recent incident. In general, there were no significant differences between participants with AHIs and control participants in most tests of auditory, vestibular, cognitive, or visual function as well as levels of the blood biomarkers. Participants with AHIs had significantly increased fatigue, depression, posttraumatic stress, imbalance, and neurobehavioral symptoms compared with the control participants. There were no differences in these findings based on the risk characteristics of the incident or geographic location of the AHIs. Twenty-four patients (28%) with AHI presented with functional neurological disorders. Conclusions and Relevance: In this exploratory study, there were no significant differences between individuals reporting AHIs and matched control participants with respect to most clinical, research, and biomarker measures, except for objective and self-reported measures of imbalance and symptoms of fatigue, posttraumatic stress, and depression. This study did not replicate the findings of previous studies, although differences in the populations included and the timing of assessments limit direct comparisons. This study assesses whether participants with anomalous health incidents (AHIs) differ significantly from US government control participants with respect to clinical, research, and biomarker assessments. [ABSTRACT FROM AUTHOR]

Modification of ecosystems as a consequence of urbanisation alters natural habitat structures and soundscapes, creating constraints for vocal communication in animals. Birds are able to adjust their vocalisation to the prevailing acoustic features of their habitat. As such, their sounds have been shown to reflect the level of anthropogenic disturbances across landscapes. While the effect of a single anthropogenic disturbance like ambient noise on birds' vocal communication is widely investigated, the combined effects of various disturbances remain less explored. We tested single and combined effects of anthropogenic noise and urban physical structures on the vocalisations of two African passerines, the Common Bulbul Pycnonotus barbatus and Northern Grey-headed Sparrow Passer griseus. We predicted that (i) both species would increase the minimum frequency of their vocalisation to avoid masking by ambient noise, (ii) both species would decrease their maximum frequency to evade distortion by physical structures, (iii) the two urban components would have a significant combined effect on the vocalisations, and (iv) the change in minimum or maximum frequency will lead to a corresponding change in the vocalisation bandwidth. For the Common Bulbul, the minimum frequency increased significantly as the ambient noise level increased, but the maximum frequency did not change in response to urban physical structures. For the Northern Grey-headed Sparrow, the minimum frequency did not show a response to ambient noise, but the maximum frequency decreased significantly as physical structures and ambient noise increased. We did not find any evidence for a combined effect of urban physical structures and ambient noise on the vocal adjustment of either species. A change in either the minimum or maximum frequency resulted in a corresponding change in the vocalisation bandwidth of each species. Our findings highlight how the same vocalisation traits of different songbird species can be affected differently by novel selective pressures in acoustic communication that arise in urban environments. [ABSTRACT FROM AUTHOR]

Advanced aerospace structures are subjected to extremely harsh working environment, including of mechanical, acoustic, thermal, and aerodynamic loads. These combined loads can make the structures exhibit complex response, which has already attracted increasing concern in the design of advanced aerospace structures. To tackle the problem, a finite element model (FEM) by discretizing the theoretical differential equation is established to calculate the dynamic response of thin-walled structures under combined thermal and acoustic loads. The numerical analysis indicates that three types of nonlinear responses of the thin plate under combined thermal-acoustic loads are obtained, and the mechanism of snap-through is revealed through two ways: thermal buckling analysis and thermal modal analysis. which can be used to explain the nonlinear response characteristics. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced polymer (CFRP) composites are widely used in lightweight structures because of their high specific strength, specific modulus, and low coefficient of thermal expansion. Additionally, the unidirectionally arrayed chopped strand (UACS) laminates have excellent mechanical properties and flowability, making them suitable for fabricating structures with complex geometry. In this paper, the damage process of UACS quasi-isotropic laminates under tensile load was tested using acoustic emission detection technology. The mechanical properties and damage failure mechanism of UACS laminates were studied combined with finite element calculation. By comparing and analyzing the characteristic parameters of acoustic emission signals such as amplitude, relative energy, and impact event, it is found that acoustic emission behavior can accurately describe the damage evolution of specimens during loading. The results show that the high-amplitude signals representing fiber fracture in continuous fiber laminates are concentrated in the last 41%, while in UACS laminates they are concentrated in the last 30%. In UACS laminates, more of the damage is caused by matrix cracks and delamination with medium- and low-amplitude signals, which indicates that UACS laminates have a good suppression effect on damage propagation. The stress–strain curves obtained from finite element analysis agree well with the experiment results, showing the same damage sequence, which confirms that the model described in this research is reliable. [ABSTRACT FROM AUTHOR]

Road traffic noise is a severe environmental hazard, to which a growing number of dwellers are exposed in urban areas. The possibility to accurately assess traffic noise levels in a given area is thus, nowadays, quite important and, on many occasions, compelled by law. Such a procedure can be performed by measurements or by applying predictive Road Traffic Noise Models (RTNMs). Although the first approach is generally preferred, on-field measurement cannot always be easily conducted. RTNMs, on the contrary, use input information (amount of passing vehicles, category, speed, among others), usually collected by sensors, to provide an estimation of noise levels in a specific area. Several RTNMs have been implemented by different national institutions, adapting them to the local traffic conditions. However, the employment of RTNMs proves challenging due to both the lack of input data and the inherent complexity of the models (often composed of a Noise Emission Model–NEM and a sound propagation model). Therefore, this work aims to propose a methodology that allows an easy application of RTNMs, despite the availability of measured data for calibration. Four different NEMs were coupled with a sound propagation model, allowing the computation of equivalent continuous sound pressure levels on a dataset (composed of traffic flows, speeds, and source–receiver distance) randomly generated. Then, a Multilinear Regressive technique was applied to obtain manageable formulas for the models' application. The goodness of the procedure was evaluated on a set of long-term traffic and noise data collected in a French site through several sensors, such as sound level meters, car counters, and speed detectors. Results show that the estimations provided by formulas coming from the Multilinear Regressions are quite close to field measurements (MAE between 1.60 and 2.64 dB(A)), confirming that the resulting models could be employed to forecast noise levels by integrating them into a network of traffic sensors. [ABSTRACT FROM AUTHOR]

The elevator door system plays a crucial role in ensuring elevator safety. Fault prediction is an invaluable tool for accident prevention. By analyzing the sound signals generated during operation, such as component wear and tear, the fault of the system can be accurately determined. This study proposes a GNN-LSTM-BDANN deep learning model to account for variations in elevator operating environments and sound signal acquisition methods. The proposed model utilizes the historical sound data from other elevators to predict the remaining useful life (RUL) of the target elevator door system. Firstly, the opening and closing sounds of other elevators is collected, followed by the extraction of relevant sound signal characteristics including A-weighted sound pressure level, loudness, sharpness, and roughness. These features are then transformed into graph data with geometric structure representation. Subsequently, the Graph Neural Networks (GNN) and long short-term memory networks (LSTM) are employed to extract deeper features from the data. Finally, transfer learning based on the improved Bhattacharyya Distance domain adversarial neural network (BDANN) is utilized to transfer knowledge learned from historical sound data of other elevators to predict RUL for the target elevator door system effectively. Experimental results demonstrate that the proposed method can successfully predict potential failure timeframes for different elevator door systems. [ABSTRACT FROM AUTHOR]

This paper presents the demonstration of underwater thermoacoustic (TA) sound generation using three-dimensional graphene (3D-C). 3D-C is able to interface with water as the immediate acoustic medium, resulting in reduced attenuation across solid packaging encapsulation due to favorable acoustic impedance matching. This is shown using array configurations of 2*2 and 4*4 individual 3D-C elements prepared onto printed circuit boards and secured within a watertight cuboid Delrin container with deionized water. Comparisons of underwater acoustic performance between internal medium of water and air shows significant improvement in measured sound pressure level (SPL) with internal water medium, in contrast with internal air medium where SPL were below noise floor. This demonstration opens up new possibilities of 3D-C for underwater acoustic applications. Simulations are conducted using 3D finite element model generated with COMSOL Multiphysics and validated with experimental results. A revised formulation of transmission voltage response (TVR) specific to TA sound generation is proposed due to the difference in power scaling of TA sound generation and subsequently validated using simulation. [ABSTRACT FROM AUTHOR]

Accurate simulation of nonlinear acoustic waves is essential for the continued development of a wide range of (high-intensity) focused ultrasound applications. In this article, we explore mixed finite element formulations of classical strongly damped quasilinear models of ultrasonic wave propagation, the Kuznetsov and Westervelt equations. Such formulations allow simultaneous retrieval of the acoustic particle velocity and either the pressure or acoustic velocity potential , thus characterizing the complete ultrasonic field at once. Using non-standard energy analysis and a fixed-point technique, we establish sufficient conditions for the well-posedness, stability, and optimal a priori errors in the energy norm for the semi-discrete equations. For the Westervelt equation, we also determine the conditions under which the error bounds can be made uniform with respect to the involved dissipation parameter. Additionally, we discuss convergence in the maximum error norm of the involved scalar quantities. Finally, computer experiments for Raviart–Thomas (RT) and Brezzi–Douglas–Marini (BDM) elements are performed to confirm the theoretical findings. [ABSTRACT FROM AUTHOR]

Detection of sound pressure level is an important factor for individuals working in noisy environments. When noise occurs in large quantities, it threatens the health and working safety of individuals working in that environment. Since it is necessary to determine periodic pressure changes to measure sound intensity, many mathematical analyzes and experimental studies have been carried out on this subject. Logarithmic equations are used in the intensity measurements of the sound and in the distribution, reduction and exposure analyzes of the sound depending on the distance. In this study, Galerkin Weighted Residues Method (WRM) and Spherical Harmonic Functions, which have been used frequently in sound problems in recent years, are used for the solution of sound wave equations in spherical coordinates, which have not been observed in the literature before, in determining the periodic pressure values of sound. Based on the directivity coefficient and spherical harmonic functions in detecting sound pressure levels in the near field, The Critical Distance Threshold, r_cri, was defined and combined with data from WRM. In this way, it was determined that the numerical sound pressure values obtained were very close to the values used in the classical logarithmic approach, and as a result of the logarithmic consistency analysis made for these numerical data. [ABSTRACT FROM AUTHOR]

• An accurate algorithm is presented for transcranial magneto-acoustic-electrical stimulation. • Unstructured mesh used in mesh discretization facilitates the pre-processing. • Our algorithm possesses higher calculation accuracy and faster convergence rate. • The developed model can achieve superior computational efficiency. • The proposed method is insensitive to mesh distortion. In this paper, a numerical method for simulating transcranial magneto-acoustic-electrical stimulation (TMAES) is presented. The smoothed finite element method (SFEM) is applied to calculate the magnetic field and the Rayleigh integral (RI) is used for solving the ultrasonic field. Three-node triangular and four-node tetrahedral elements are set as the background cells for constructing the smoothing domains (SDs). A gradient smoothing technique (GST) is applied over each SD to obtain the magnetic flux density. The discretized system equations are obtained by using the generalized smoothed Galerkin weakform. To solve the sound pressure, the ultrasonic transducer is discretized into a series of micro-elements. The acoustic pressure in the problem domain is then equal to the superposition of that generated by the individual micro-element. Finally, the current density can be calculated by the magneto-acoustic coupling effect. Numerical examples demonstrate that SFEM can improve accuracy, convergence rate, and efficiency to 10, 1.8, and 4 times those of FEM, respectively. In the calculation of coupled fields, SFEM-RI also improves the accuracy by 2.5 times. Additionally, the presented method possesses the property of insensitivity to mesh distortion. [ABSTRACT FROM AUTHOR]

The advantages of adjustable angle phase-shifting and great expansibility make the linear phase-shifting transformer a novel type of power conversion device with a wide range of potential applications. However, during the procedure, there is a lot of noise. For the purposes of transformer design and vibration and noise reduction, it is crucial to investigate its electromagnetic vibration and noise. In this paper, the radial electromagnetic force wave considering the influence of the end effect as the source of the noise of the linear phase-shifting transformer was deduced and calculated. Based on this, the spectrum and space–time properties of the radial electromagnetic force waves were simulated and verified. Additionally, a finite element model was created using the Ansys Workbench 2022R1 platform to study the electromagnetic vibration and noise of the linear phase-shifting transformer. A joint simulation of the electromagnetic, structural, and sound fields was then performed. First, the transformer's natural frequency was determined by modal analysis. After that, the transformer's structure and the results of the transient electromagnetic field computation were combined and a harmonic response analysis was conducted to determine the vibration acceleration spectrum. Finally, in order to solve the sound pressure field, the transformer's boundary vibration acceleration was coupled to the air domain. Furthermore, an analysis was conducted to determine the noise distribution surrounding the linear phase-shifting transformer. The joint simulation findings demonstrate that the linear phase-shifting transformer's resonance, which produces larger electromagnetic vibration and noise, is indeed caused by the radial electromagnetic force. Simultaneously, the impact of the LPST core's fixed components on the electromagnetic vibration and noise of the core was examined. [ABSTRACT FROM AUTHOR]

Herein, we report a conversion of the solid-state shape of an amino acid material, namely L -tyrosine, from irregular to rod shapes as a result of its processing of acoustic shock waves, and we explain the obtained results using the concepts of dynamic recrystallization. The initial L -tyrosine sample crystallizes in the P212121 space group with irregular shapes—but when subjected to shocks, transforms into essentially perfect rod shapes, especially when subjected to 200 shock pulses. From X-ray diffraction results, it is also found that the ratio of the intensity of the (130) peak to that of the (111) peak is significantly reduced from 3.183 to 1.298 upon subjecting the L -tyrosine sample to 200 shock pulses, with this latter value matching quite well that in the standard XRD pattern of the title sample. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric sensors have been spotlighted as an essential human–machine interface (HMI) by obtaining high‐quality data from omnipresent biomechanical inputs. Because human voice is the most intuitive bio‐signal among them, flexible piezoelectric acoustic sensors (f‐PAS) have a potential to shift the paradigm of HMI technologies. Despite the reported outstanding performance such as high sensitivity and speaker recognition accuracy, the theoretical investigation of f‐PAS has been insufficient to realize future customized development, because sensing principles are fundamentally different from commercialized microphones. Here, a theoretical framework of self‐powered f‐PAS by using mechanical and electrical physics is introduced. First of all, the basic theory of f‐PAS is compared with the auditory system of human cochlear. Based on the biomimetic trapezoidal shape, the resonant frequencies are analyzed with various structural and material conditions. In addition, the piezoelectricity of f‐PAS is derived to predict the sensitivity and SNR prior to experiments. To investigate sensor properties under the medium condition that is similar to human ear, the acoustic responses depending on the states of matter are theoretically compared. Finally, the distance limit of f‐PAS is studied with the correlations between piezoelectricity and sound pressure, which would provide novel strategies of functional material design for future applications of f‐PAS. [ABSTRACT FROM AUTHOR]

The accuracy of defect localisation and its size quantification is poor in the detection of internal defects of cylindrical components using the ultrasonic Amplituden und Laufzeit Orts-Kurven (ALOK) method. The influence of acoustic beam spread is not taken into consideration in the ultrasonic ALOK method, resulting in difficulties with the precise characterisation of the defect state. To address this, the relationship between the acoustic distance, amplitude, ultrasonic frequency, size and depth of hole defects was studied. The acoustic distance curve and the amplitude curve were fitted and then the localisation model of the defect was obtained. The acoustic beam spreading angle and echo sound pressure were introduced and then the size quantification model for defects was acquired based on principal component analysis (PCA). Both the simulated and experimental results show that the modified ALOK algorithm improved the detection accuracy of the defect location and its size and the relative error of defect sizing decreased by more than 35% compared with the original algorithm. [ABSTRACT FROM AUTHOR]

This numerical simulation study has been performed to investigate the dynamic characteristics, oscillation characteristics, and sound pressure of direct contact condensation at low steam mass flux. The volume of fluid model, Ffowcs Williams and Hawkings model, and condensation model are used to simulate the acoustic signal, which is produced during the steam injection process. The simulation results are verified by the experimental results to keep the applicability and accuracy of the model. The results show that the acoustic signal is related to the steam flow patterns. The vibration of the bubble volume, caused by the separation of bubbles, is the important factor for the generation of the acoustic signal. When the subcooled temperature is large, the chugging regime appears during the injection process. The sound pressure amplitude of the steam injection process increases significantly, with the increase in subcooled temperature. In the low-frequency region, which is below 10 Hz, the larger the subcooled temperature increases, the greater the sound pressure amplitude becomes. [ABSTRACT FROM AUTHOR]

Partial Discharges (PDs) are a significant factor in reducing the insulation life of traction transformers. In recent years, the Acoustic Emission (AE) method has become the most advanced method for detecting PD signals in transformers. The AE method utilizes AE sensors placed on the transformer tank to detect ultrasonic signals emitted by PD and determine the Time Of Arrival (TOA) of the head wave. The windings and cores of a traction transformer consist mainly of metal, which greatly affects the propagation of PD ultrasonic waves. This paper establishes a 110 kV "pressure acoustic, transient" physical field model of the traction transformer with dimensions of 4.63 × 1.48 × 2.84 m3. The model is used to carry out the PD pressure acoustic physical field simulation study of the traction transformer, to clarify the physical characteristics of the ultrasound of the PD defects, and to establish observation points on the transformer tanks to receive ultrasonic time-domain waveforms for PD detection. The simulation results indicate that PD ultrasonic waves exhibit complex propagation characteristics, including reflection, refraction, and reverberation, as they pass through the windings and cores to the observation points. The TOA of the head wave in the ultrasound time-domain waveform is indicated by the first maximum value of the wave crest line. Finally, this paper proposes a multi-level localization method based on the AE method to determine which winding generates the PD in the large-scale traction transformer using only four dynamically moving observation points. [ABSTRACT FROM AUTHOR]

Sound field separation techniques are an advancing tool for extracting a target sound field from a mixed sound field. However, the methods bear a high measurement cost due to the restriction of the sampling theorem. In this study, a sound field separation method based on sparse sampling is established. The method initially utilizes dictionary learning to generate a sparse basis of the sound field. Then, a mixed sound field can be precisely recovered from sparse sampling of sound pressure and the target sound field can be extracted based on the recovered sound field by means of the theory of equivalent source method. The method is validated by numerical simulations. Compared to sound field separation based on the equivalent source method, the proposed method has advantage in terms of both the accuracy and the stability for sparse sampling. [ABSTRACT FROM AUTHOR]

Background: Long‐term non‐traumatic noise exposure, such as heavy traffic noise, can elicit emotional disorders in humans. However, the underlying neural substrate is still poorly understood. Methods: We exposed mice to moderate white noise for 28 days to induce anxiety‐like behaviors, measured by open‐field, elevated plus maze, and light–dark box tests. In vivo multi‐electrode recordings in awake mice were used to examine neuronal activity. Chemogenetics were used to silence specific brain regions. Viral tracing, immunofluorescence, and confocal imaging were applied to define the neural circuit and characterize the morphology of microglia. Results: Exposure to moderate noise for 28 days at an 85‐dB sound pressure level resulted in anxiety‐like behaviors in open‐field, elevated plus maze, and light–dark box tests. Viral tracing revealed that fibers projecting from the auditory cortex and auditory thalamus terminate in the lateral amygdala (LA). A noise‐induced increase in spontaneous firing rates of the LA and blockade of noise‐evoked anxiety‐like behaviors by chemogenetic inhibition of LA glutamatergic neurons together confirmed that the LA plays a critical role in noise‐induced anxiety. Noise‐exposed animals were more vulnerable to anxiety induced by acute noise stressors than control mice. In addition to these behavioral abnormalities, ionized calcium‐binding adaptor molecule 1 (Iba‐1)‐positive microglia in the LA underwent corresponding morphological modifications, including reduced process length and branching and increased soma size following noise exposure. Treatment with minocycline to suppress microglia inhibited noise‐associated changes in microglial morphology, neuronal electrophysiological activity, and behavioral changes. Furthermore, microglia‐mediated synaptic phagocytosis favored inhibitory synapses, which can cause an imbalance between excitation and inhibition, leading to anxiety‐like behaviors. Conclusions: Our study identifies LA microglial activation as a critical mediator of noise‐induced anxiety‐like behaviors, leading to neuronal and behavioral changes through selective synapse phagocytosis. Our results highlight the pivotal but previously unrecognized roles of LA microglia in chronic moderate noise‐induced behavioral changes. [ABSTRACT FROM AUTHOR]

The propagation of the weak shock wave (WSW) to the tunnel exits and their radiation as micro-pressure waves (MPWs) may cause sonic booms or structural resonance of buildings, posing potential hazards to humans, animals, and buildings in the exit's environment. The characteristics of the WSW and sonic booms of a maglev train/tube coupling model were studied based on the two-dimensional axisymmetric unsteady Reynolds average Navier–Stokes turbulence model. In the later stage of a MPW, the formation mechanism, geometry, and kinematic characteristics of compressible vortex rings (CVRs) were systematically analyzed. The inertial effect causes the initial wavefront to gradually transition from a Gaussian-shape waveform to a triangular waveform during its propagation, eventually coalescing into a WSW. The overpressure, density jump, and shock Mach number at the WSW location all increase with the increasing train speed, while the WSW thickness decreases accordingly. The formation distance of the WSW is inversely proportional to the amplitude of the initial wavefront gradient, and the WSW directly causes the occurrence of the exit sonic boom. The MPW amplitude has significant directionality with a largest value in the axial direction. Within the speed range of 450–700 km/h, the sound pressure level of the MPW exceeds the hearing threshold and even reaches the feeling threshold. The evolution of CVRs includes primary CVR, secondary CVR, and Kelvin–Helmholtz vortices. Primary CVR has the greatest impact on the axial MPW among them. The occurrence of CVRs will cause a second small noise level other than the sonic boom. [ABSTRACT FROM AUTHOR]

In this work, we implement an asymptotic expansion technique that leverages a small perturbation parameter that arises in the context of one-dimensional tubes with open-open end point configurations and spatially varying heat sources. This approach, when paired with a spectral collocation eigensolver, enables us to produce accurate predictions of the pressure mode shapes and frequencies over a wide range of parameters. These include the temperature gain across the heat source, the heat source length and location, and the overall thermal profile. The latter is intended to reproduce different flow heating configurations that emulate Rijke tube characteristics. Specifically, this investigation begins by considering three piecewise representations of the heat source by juxtaposing constant–constant temperatures before and after a heating element whose temperature is prescribed locally using three analytical functions: linear, exponential, and power-law profiles. This is followed by a logistic distribution that can be globally applied to provide a uniformly valid, continuous, and differentiable thermal profile spanning the entire tube, including the heat source element. Our fundamental formulation relies on Green's functions and an integral formulation that enables us to extract all acoustic frequencies analytically. These are found to increase monotonically with successive elevations in the temperature gain across the heat source, retractions of the heat source, length reductions in the heat source, and smoothing of the temperature gain. Along similar lines, the pressure mode shapes are found to exhibit blunter and often linear variations for higher temperature gains, longer heat sources, and upstream displacements of the heat source toward the inlet. [ABSTRACT FROM AUTHOR]

Cavitation noise, mainly from bubble cluster collapse, is a primary source of noise in underwater equipment. This study aims to elucidate the acoustic characteristics of bubble clusters with varying volume fractions (0.002%–43%), thereby illuminating the noise patterns generated during bubble cluster collapse. With the direct numerical simulation (DNS) method, we simulate the collapse of bubble clusters containing 352 vapor bubbles. Far-field sound pressure was calculated by using the Farassat 1 A integral solution of the Ffowcs Williams–Hawkings (FW–H) equation. The results show that when the volume fraction of bubble clusters is greater than 20%, the higher the volume fraction, the closer the far-field sound pressure radiated by its collapse is to that of the equivalent bubble (whose volume is equal to the volume of the bubble cluster), and when the volume fraction is greater than 30%, the sound pressure of the bubble cluster is basically the same as that of the equivalent bubble. Furthermore, when the volume fraction of bubble clusters is less than 1%, the lower the volume fraction is, the closer the sound pressure obtained through the superposition of a single bubble (each with an initial radius equal to that within clusters and in a free field) is to that of bubble clusters, and when the volume fraction is less than 0.1%, the bubble clusters' sound pressures agree with those obtained through superposition. This study reveals the far-field noise pattern generated by the collapse of bubble clusters, providing a theoretical basis for the prediction of cavitation noise. [ABSTRACT FROM AUTHOR]

To determine their frequency-dependent susceptibility to noise-induced temporary hearing threshold shift (TTS), two California sea lions (Zalophus californianus) were exposed for 60 min to a continuous one-sixth-octave noise band (NB) centered at 32 kHz as the fatiguing sound, at sound pressure levels of 132 to 156 dB re 1 µPa (sound exposure levels [SELs] of 168 to 192 dB re 1 µPa2s). Using a psychoacoustic technique, TTSs were quantified at the center frequency of the fatiguing sound and at half an octave and one octave above the center frequency (at 32, 44.8, and 63 kHz). When significant TTS occurred, higher SELs resulted in greater TTSs. TTSs and hearing recovery patterns were similar in both sea lions. The mean onset of TTS1-4 min (defined as 6 dB TTS) in sea lion F01 is estimated to occur after exposure to an SEL of 179 dB re 1 µPa²s (at hearing test frequency 44.8 kHz). After exposure to an SEL of 180 dB re 1 µPa2s, a mean TTS1-4 min of 6.7 dB was measured at hearing test frequency 44.8 kHz. In California sea lions, TTS onset levels are not as closely related (especially at the lower and higher frequencies) to the unmasked hearing thresholds (audiograms) as was previously assumed. [ABSTRACT FROM AUTHOR]

Reorganization of neonatal intensive care by introducing clinical microsystems may help to allocate nursing time more appropriately to the needs of patients. However, there is concern that cohorting infants according to acuity may enhance noise levels. This single-center study investigated the impact of reorganization of neonatal intensive care unit by implementing clinical microsystems in a Level III NICU on environmental noise. This prospective study measured 24-h noise levels over a period of 6 months during pre- and post-implementation of microsystems cohorting infants of similar acuity. Comparative analyses of the mixed acuity (i.e., before) and the cohorting (i.e., after) model were performed by creating daily profiles from continuous noise level measurements and calculating the length of exposure to predefined noise levels. Compared to baseline daytime measurements, noise levels were 3–6 dBA higher during physician handover. Noise levels were 2–3 dBA lower on weekends and 3–4 dBA lower at night, independent of the organizational model. The introduction of clinical microsystems slightly increased average noise levels for high-acuity pods (A and B) but produced a much more substantial decrease for low-acuity pods (E), leading to an overall reduction in unit-wide noise levels. Conclusion: Our data show that noise levels are more driven by human behavior than by technical devices. Implementation of microsystems may help to reduce noise exposure in the lower acuity pods in a NICU. What is Known: • Excessive noise levels can lead to adverse effects on the health and development of premature infants and other critically ill newborns. • The reorganization of the neonatal intensive care unit following the clinical microsystems principles might improve quality of care but also affect noise exposure of staff and patients. What is New: • The transition from a mixed -acuity to cohorting model is associated with an overall reduction in noise levels, particularly in low-acuity pods requiring less nursing care. • Nevertheless, baseline noise levels in both models exceeded the standard permissible limits. [ABSTRACT FROM AUTHOR]

To study the influence of the blade curvature radius on the flow‐induced vibration and noise of the centrifugal pump, the internal sound field of the IS 80‐65‐160 centrifugal pump was numerically calculated by adjusting the blade wrap angles to change the blade curvature radius. The RNG k−ε $k-\varepsilon $ (Reynolds Time Average Simulation) turbulence model was selected for the numerical calculation of the centrifugal pump. The numerical simulation of the whole flow channel of the centrifugal pump was carried out using Ansys Fluent software, and the external characteristic curve of the centrifugal pump was obtained. The influence of different blade wrap angles on the internal pressure, velocity and Turbulent Kinetic Energy of the centrifugal pump was obtained. On the basis of the sound–structure coupling equation, the unsteady sound field of the centrifugal pump was calculated, and the time domain and frequency domain characteristics of the pressure pulsation at each monitoring point were obtained. The calculation results showed that the dynamic and static interference between the impeller and the volute tongue mainly caused the vibration of the centrifugal pump. By appropriately increasing the blade wrap angles, the pressure pulsation in the volute fluid domain could be effectively reduced. The vibration and noise test bench of the centrifugal pump was set up to verify the test. The experimental results showed that at the double‐blade frequency, the variation trend of the experimental value and the simulated value of the outflow flow‐induced noise of the centrifugal pump were consistent, which verified the accuracy of the sound field simulation calculation. When the blade wrap angle φ=125∘ $\varphi ={125}^{\circ }$, it could effectively reduce the internal sound pressure level and the flow‐induced vibration and noise of the centrifugal pump. By adopting measures such as grid encryption at the position of the tongue, nonstationary calculation and comparison of different turbulence models, the accuracy of the calculation results of the internal flow field and sound field of the centrifugal pump is effectively improved, and the accuracy and reliability of the experimental results are ensured. The above research results had certain reference significance and application value for improving the working efficiency of centrifugal pumps and reducing flow‐induced vibration and noise. [ABSTRACT FROM AUTHOR]

We propose an iterative method for solution of a coupled acoustic fluid-solid interaction model. Assuming harmonic excitation in time, we use the pressure-displacement formulation of the acousto-elastic problem. The fluid is assumed to be ideal inviscid compressible medium governed by a wave equation for the acoustic pressure. The linear isotropic elastic structure is described by elastodynamic equations for the displacement field. We impose kinematic and dynamic conditions at the interface: the fluid particles velocity matches the velocity of the solid, and the balance of normal stresses holds. In the proposed iterative method. The fluid and solid subproblems are solved alternatingly, taking into account the interface conditions. The convergence of the iterative algorithm is demonstrated numerically for fluid-solid structures with different periodic, as well as random interfaces. The algorithm is applied for comparison of acoustic properties of fluid-solid structures depending on the geometry of the rough interface. [ABSTRACT FROM AUTHOR]

The investigation into aerodynamic noise arising from rotating surfaces bears significant practical implications. Among these, engine cooling fans have persistently been identified as primary contributors to vehicle noise. This study aims to provide a deeper comprehension of the complex unsteady flow dynamics surrounding an automotive cooling fan and its consequential impact on the generation of aerodynamic noise. Prediction of sound generated from fluid flow, despite its difficulty, can be simulated using modern numerical techniques and computational fluid dynamics (CFD). This research undertakes both numerical and experimental investigations. The experiment involves evaluating fan pressure against mass flow rate at 1500 rpm, while aerodynamic noise assessment transpires at two rotational speeds of 1500 rpm and 2500 rpm. Empirical sound pressure level data of the fan is meticulously captured using the requisite measurement apparatus. In addition, numerical investigations of the aerodynamic noise of an automotive cooling fan based on computational fluid dynamics and computational aeroacoustic (CAA) method have been performed. Initially, a steady-state aerodynamic simulation is carried out, followed by the simulation of the flow field through the application of the improved delayed detached eddy simulation (IDDES) formulation. The pressure rise of the fan versus the mass flow rate is obtained. The satisfactory concurrence observed between the simulation outcomes derived from the numerical method and the experimental dataset stands as notable validation. For the aeroacoustic computation, the Ffowcs Williams-Hawkings model is invoked to deduce sound pressure levels at specific flow points. The broadband noise sources model is also used to obtain the sound power level on the blade surface. Conclusively, it emerges that maximal noise manifestation occurs at a 90° degree angle, corresponding to the hub's frontal orientation, with discernible dominance of tonal noise within lower frequency ranges (sub-1000 Hz). [ABSTRACT FROM AUTHOR]

An experiment is conducted in a multistage high-pressure compressor to investigate noise and rotor blade vibration. When vibration with high amplitude occurs in the rotor blade, high-intensity sound occurs within the compressor. The amplitude of noise inside the compressor varies with the amplitude of blade vibration, and the variation laws are consistent. Therefore, an annular disk cavity model, the simplified cavity between the rotator and stator of a high-pressure compressor, is built to study the high-intensity sound in the compressor by numerical simulation. The motion processes of the vortex structure inside the cavity are captured. The acoustic mode of the annular disk cavity model is excited at Ma 0.2, at the same time the sound pressure in the cavity is characterized with obvious a form of circumferential second order. The internal sound pressure gradually increases along the radial direction. Meanwhile, an annular disk cavity structure is established for experimental study. The characteristics of the acoustic mode of the annular disk cavity structure obtained in the simulation and experiment are consistent. [ABSTRACT FROM AUTHOR]

The tiltrotor design is favored for urban air mobility (UAM) prototypes due to the combination of vertical takeoff and landing (VTOL) capability and efficient forward flight. With rising UAM air traffic at low altitudes, noise from these aircraft is a crucial design factor. Most tiltrotor noise research focuses on high disk loading and Reynolds number setups, leaving smaller aircraft configurations less explored. This study investigates aero-acoustic trends from rotor-wing interaction at low disk loading (< 100 N/m2) and Reynolds number (Re < 100,000). While prior literature suggests lowering disk loading and reducing rotor wake interference can mitigate rotor noise, such ideas lack empirical validation. The setup involves an anechoic chamber housing a two-blade rotor, along with flat and NACA 0012 airfoil wings. Microphones and a rotation stage capture acoustic data for analysis. Factors like flow recirculation, isolated rotor noise, rotor height, rotation direction/rate, and wing curvature are assessed for impact on noise signature. It is found that the deflected rotor wake in rotor-wing interaction significantly increases low-frequency broadband noise and overall sound pressure level (OASPL), compared to an isolated rotor. Dominant tonal noise diminishes based on the strength of the deflected rotor wake. These findings offer insights into reducing noise from rotor wake impingement on the wing. [ABSTRACT FROM AUTHOR]

Several techniques are available to characterize acoustic liners when subject to grazing flow and high sound pressure level (SPL). Although the in situ technique started as the primary experimental procedure, impedance eduction techniques have gained popularity over the past years. However, there is a lack of comparison between these group of methods, especially at conditions typically found in turbofan engines. In this work, in situ and impedance eduction techniques are compared at high flow velocities and SPL using typical acoustic liner test samples and considering uniform flow. Both upstream and downstream acoustic wave propagation will also be considered in view of the discrepancies recently observed by eduction methods. A new method to compensate the instrumentation effect in the in situ technique is proposed and validated. Results are obtained for bulk Mach numbers up to 0.5 and SPLs up to 145 dB for both in situ and two eduction techniques. The three methods presents good agreement in the absence of flow. Unexpected results are observed with higher flow Mach numbers using the eduction technique. [ABSTRACT FROM AUTHOR]

This experimental investigation is aimed at assessing how the introduction of a cross-wire at the exit of a CD nozzle influences the performance of a supersonic nozzle. The study focuses on cold air jets generated by De Laval nozzles equipped with cross-wires and baseline configurations, particularly at design Mach numbers of 1.5 and 1.75. The investigation involves collecting measurements from the noise field emitted by the cross-wire nozzle with a 2% obstruction at the exit. This passive control approach effectively reduces the occurrence of screech tones in both over-expanded and under-expanded conditions in the azimuthal plane at appropriate operating pressures. Various acoustic parameters, including sound pressure levels (SPL), Strouhal numbers, and the overall sound pressure level spectra (OASPL) are recorded. Schlieren imaging captures images of shock cell patterns, illustrating the impact of shock-associated noise. In comparison to a baseline nozzle, the results demonstrate that a CD nozzle equipped with a cross-wire proves to be a proficient screech tone suppressor, leading to an average reduction of up to 5 dB in OASPL in under-expanded and over-expanded scenarios. [ABSTRACT FROM AUTHOR]

Objectives: To determine the relationship between occupational noise, and obesity and body mass index (BMI) changes. Methods: Baseline data were collected from participants (n = 1264) who were followed for 6 years in a retrospective study. The noise exposure level (LAeq,8h) was determined by equivalent continuous weighted sound pressure levels using the fixed-point surveillance method for noise monitoring. The cumulative noise exposure (CNE) level was determined using the equal energy formula, which is based on exposure history and level. Results: The incidence of obesity at low (RR = 2.364, 95% CI 1.123–4.739]), medium (RR = 3.921, 95% CI 1.946–7.347]), high (RR = 5.242, 95% CI 2.642–9.208]), and severe noise levels (RR = 9.322, 95% CI 5.341–14.428]) was higher risk than the LAeq,8h control level. The risk of obesity among participants exposed to low (RR = 2.957, 95% CI 1.441–6.068]) and high cumulative noise levels (RR = 7.226, 95% CI 3.623–14.415]) was greater than the CNE control level. For every 1 dB(A) increase in LAeq,8h, the BMI increased by 0.063 kg/m2 (95% CI 0.055–0.071], SE = 0.004). For every 1 dB(A) increase in the CNE, the BMI increased by 0.102 kg/m2 (95% CI 0.090–0.113], SE = 0.006). Conclusions: Occupational noise is related to the incidence of obesity. The occupational noise level and occupational noise cumulative level were shown to be positively correlated with an increase in BMI. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring (PAM) is useful for monitoring vocal fish but has had so far limited application in fisheries management. Here, four years (2016–2019) of concurrent daily catch and effort fishery data in Portugal and species-specific vocal activity in the Tagus estuary are compared to describe biological and small-scale fishery dynamics for a large sciaenid fish, the meagre (Argyrosomus regius), that aggregates to spawn. Consistent patterns in seasonality of acoustic and fisheries variables indicate that most fishing takes place within the Tagus estuary in spring and summer months, when higher vocal activity related to spawning aggregations is detected in the PAM station. Good fit of statistical models shows that PAM (sound pressure level in the third-octave band with centre frequency at 500 kHz during dusk) and PAM-supported variables (mean weekly catch per first sale transaction) can provide useful surveillance indicators to improve local management. Signs of overexploitation and hyperstability are detected and communicated to the estuarine fishing communities with the aim to initiate an adaptive local management cycle. The approach can be relevant for fisheries targeting other vocal fish that seasonally aggregate and face similar threats of overexploitation. [ABSTRACT FROM AUTHOR]

In the present work, we report acoustic shock wave recovery experimental findings on cubic zinc sulfide nanoparticles (ZnS NPs) with crystallographic, electronic and magnetic phase stability. The acquired X-ray diffraction (XRD) and magnetic results show that the ZnS NPs have a stable cubic crystalline structure, and however, owing to the reduction in defects, they result in reversible magnetic phase transitions from the weak-ferromagnetic to mixed-diamagnetic/ferromagnetic states at the corresponding 50 and 150 shocked conditions. The values of saturation magnetization are determined as 0.249, 0.052, 0.249 and 0.049 emu/g for 0, 50, 100 and 150 shocked conditions, respectively. Accordingly, the magnitude of the calculated band gap energies for 0, 50, 100 and 150 shocked conditions are identified to be 3.70, 3.85, 3.69, and 3.85 eV, respectively. Furthermore, the double peaks at corresponding positions of 161.67 (S 2p 3/2) and 162.97 (S 2p 1/2) of the X-ray photoelectron spectroscopy (XPS) are converted into the singlet peak at 162.23 (S 2p 1/2), demonstrating the reduction of the defect density at the 50-shocked condition. Finally, the structure-property relationship of cubic ZnS NPs and magnetic properties with respect to the exposed shocks are discussed in detail. Due to the switchable optical and magnetic properties by the number of shock pulses, cubic zinc sulfide nanoparticles can be suitable for spintronics devices and magnetically switchable applications. [ABSTRACT FROM AUTHOR]