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Period phase gradient metasurface plays a great role in promoting the innovation of acoustic application devices. However, harnessing the internal thermal viscosity of the period phase gradient metasurface to realize sound absorption and non-reciprocal transmission faces the narrow working frequency band and uncontrollable efficiency. In this paper, we propose a lossy metasurface by embedded microperforated walls to realize sound redirection and absorption with high efficiency than 90% simultaneously. The phase modulation is realized using an opening channel, which can cover the 2 π phase range in a broadband frequency range by changing the channel depth. The loss introduced by the microperforated walls can achieve efficient sound energy dissipation when negative reflection occurs. The functions can be switched between wave redirection and wave absorption by rotating the metasurface. In addition, this metasurface can redirect the incident wave below −10° and absorb the incident wave above 25° over a wide frequency range from 1500 to 6500 Hz. The simulation and experiment results of our design are in excellent agreement. This research provided a new bridge to integrate wave redirection and absorption with microperforated walls and may have potential applications in acoustic sensing, sound source identification, and mechanical fault diagnosis. [ABSTRACT FROM AUTHOR]

Acoustic black hole (ABH) is a technique capable of manipulating the propagation of flexural wave, and the sonic black hole (SBH) is a kind of ABH which is used to manipulate sound wave in a fluid medium. In this paper, we propose an SBH structure with labyrinthine units and combine with micro-perforated panel (MPP) to form a composite sound absorption structure. The sound absorption mechanism of the absorption structure is deeply investigated using numerical and simulation methods. The simulation reveals the sound absorption mechanism by acoustic streaming effects of composite sound absorption structure. We analyze the flow characteristics of the acoustic medium under acoustic excitation, and the effect of the flow field on the distribution of the acoustic field, and the energy dissipation distribution. Our theoretical results show that the sound absorption is attributed to the effects of sound energy focusing of ABH, the local resonance of MPP, and the acoustic energy localization and dissipation effect of labyrinthine units caused by large flow velocity gradients. Finally, the proposed composite sound absorption structure has good sound absorption performance, which is also confirmed by impedance tube experiments. It can provide a new way of thinking for the design and optimization of the SBH structure. [ABSTRACT FROM AUTHOR]

The research investigates the sound absorption properties of potassium polyacrylate (PPA) composites, particularly those augmented with clay and porous hollow glass beads within a hydrogel template. This unique material combination shows promise for efficient sound absorption, relevant in industries requiring effective noise control like acoustic engineering and construction. Experimental assessment focused on measuring the sound absorption coefficient, crucial for quantifying a material's ability to absorb sound energy across various frequencies. Incorporating clay and porous hollow glass beads introduces complexities, emphasizing the need for precise acoustic performance prediction. Collected data from sound absorption coefficient measurements formed the basis for training an Artificial Neural Network (ANN) model. Leveraging the ANN's pattern recognition capabilities, the model learned from diverse composite compositions, enabling accurate prediction of sound absorption coefficients for varying material compositions. This predictive model streamlines material design, offering a systematic approach to tailor composite acoustic characteristics. Integration of machine learning, particularly ANNs, enhances accuracy and expedites material design and optimization, contributing to innovative and customizable sound-absorbing materials for diverse industrial applications. [ABSTRACT FROM AUTHOR]

Mechanical energy, specifically in the form of ultrasound, can induce pressure variations and temperature fluctuations when applied to an aqueous media. These conditions can both positively and negatively affect protein complexes, consequently altering their stability, folding patterns, and self-assembling behavior. Despite much scientific progress, our current understanding of the effects of ultrasound on the self-assembly of amyloidogenic proteins remains limited. In the present study, we demonstrate that when the amplitude of the delivered ultrasonic energy is sufficiently low, it can induce refolding of specific motifs in protein monomers, which is sufficient for primary nucleation; this has been revealed by MD. These ultrasound-induced structural changes are initiated by pressure perturbations and are accelerated by a temperature factor. Furthermore, the prolonged action of low-amplitude ultrasound enables the elongation of amyloid protein nanofibrils directly from natively folded monomeric lysozyme protein, in a controlled manner, until it reaches a critical length. Using solution X-ray scattering, we determined that nanofibrillar assemblies, formed either under the action of sound or from natively fibrillated lysozyme, share identical structural characteristics. Thus, these results provide insights into the effects of ultrasound on fibrillar protein self-assembly and lay the foundation for the potential use of sound energy in protein chemistry. [ABSTRACT FROM AUTHOR]

The pursuit of robust and enhanced acoustic sensing has garnered significant attention across multiple fields of acoustic engineering. Here, we propose a feasible approach to realizing sound energy enhancement along the interface of two topologically distinct materials in an acoustic topological waveguide (ATW) with a gradient gap width. By adjusting the width of the topological bandgap, the sound energy can be localized within a desired region. Benefiting from topological protections, the confinement process is immune to certain types of defects. Our ATW is constructed using two types of C3-symmetric sonic crystals through topology optimization to extremely enlarge the width of the bandgap. Both numerical and experimental results confirm the robust edge states and enhanced energy confinement, even in the presence of non-spin-mixing defects. This work represents an advancement in the design of acoustic functional devices and may inspire potential applications in areas such as acoustic imaging, energy harvesting, and communication systems. [ABSTRACT FROM AUTHOR]

Passive source detection is a challenging problem in the shadow zone, where the sound is contributed primarily by bottom‐bounce rays. The conventional beamforming detector (CBFD), which utilises the sound energy from a single direction, suffers potential significant performance degradation in the multipath‐signal scenario. The matched field detector (MFD) offers optimal performance by exploiting full‐wave field characteristics but is limited due to its reliance on prior ocean environmental knowledge. The authors demonstrate that the incident sound on a near‐surface vertical line array in the shadow zone can be approximated as a coherent sum of two plane waves that share a symmetric arrival angle about the horizontal. This leads to the signal subspace depending only on the arrival angle, which the authors call the bottom‐bounce ray angle subspace (BRAS). With generalised likelihood ratio test theory, the authors further derive the BRAS detector (BRASD). It can utilise the full signal energy under the premise of weak environmental knowledge requirements and is generally superior to the CBFD. Simulation results in a typical deep‐water channel under different source‐position and array configuration conditions demonstrate the effectiveness of the BRASD and suggest that it can even offer a performance comparable to that of the MFD under specific conditions. [ABSTRACT FROM AUTHOR]

Ultrasound imaging has been widely used in clinical examination because of portability, safety, and low cost. However, there are still some main challenges of imaging quality that remain in conventional ultrasound systems. Improving image quality of SA-based methods using an improved imaging mode named far-focus compound (FSC) imaging. A far-focus compound (FSC) imaging based on full-aperture transmission and full-aperture reception is proposed in this paper. In transmission, it uses the full aperture to transmit the focused beam to ensure image resolution and emission of sound field energy. In reception, the full aperture is used to receive the reflected beam to ensure the image quality. A lag-one coherence-based zero-cross factor (LOCZF) is then implemented in FSC for improvement of contrast ratio (CR). The LOCZF uses lag-one coherence as zero-cross factor’s adaptive coefficient. Comparisons were made with several other weighting techniques by performing simulations and experiments for performance evaluation. Results confirm that LOCZF applied to FSC offers a good image contrast and simultaneously the speckle pattern. For simulated cysts, CR improvement of LOCZF reaches 194.1%. For experimental cysts, CR improvement of LOCZF reaches 220%. From the in-vivo result, compared with FSC, CR improvement of LOCZF reaches 112.7%. Proved gCNR performance. In addition, the LOCZF method shows good performance in experiments. The proposed method can be used as an effective weighting technique for improvement of image quality in ultrasound imaging. [ABSTRACT FROM AUTHOR]

Owing to its impedance properties and piezoelectric effect, the piezoelectric polymer polyvinylidene fluoride (PVDF) finds application in the field of noise control. Traditional sound-absorbing materials have gradually fallen short of the demands of sound-absorbing functionality and environmental adaptability in today's increasingly acute noise pollution environment. When PVDF is added to sound absorption, materials or structures have an additional loss path for the conversion of sound energy to electric energy. This helps to increase the low-frequency sound absorption band and improve low-frequency sound absorption performance. Through the action of viscosity, friction, relaxation, piezoelectric effect, and dielectric loss, the sound energy in the passive sound-absorbing material containing PVDF is transformed into energy dissipation in the form of heat energy, electric energy, and so on under the matching of PVDF low impedance. In active control, secondary sound and force sources can be supplied by PVDF-based transducers and actuators to reduce noise. This paper first provides an overview of the piezoelectric characteristics of β-phase PVDF and its optimization techniques. It then goes on to discuss the use of PVDF in passive sound-absorbing materials, active controls, and hybrid sound absorption systems. Finally, it summarizes the benefits, issues that still need to be resolved, and future directions for these three noise reduction techniques. [ABSTRACT FROM AUTHOR]

Proposals for new absorber designs for broadband sound absorption are of great interest due to their wide applicability in sound energy control. In this sense, the behavior of an acoustic absorber composed of a panel with slit-type perforations based on Cantor's fractal is presented. The analytical model for the fractal porosity of the absorber as a function of the initial geometric parameters, the number of iterations, and the fractal dimension was established. The behavior of broadband sound absorption was evaluated theoretically, numerically, and experimentally, in which the predominant total thermal-viscous dissipation in the region of perforations increases as the fractal porosity of the absorber decreases. Furthermore, an experimental broadband sound absorption of 692 Hz (from 382 to 1074 Hz) with a peak amplitude greater than 80% is obtained with the proposed structure presenting a sub-wavelength scale, i.e., λ / 27. Finally, this work contributes to the understanding of the use of Cantor's fractal porosity in the proposal of new absorbers that allow broadband sound absorption at low frequency. [ABSTRACT FROM AUTHOR]

This paper investigates the acoustic streaming effects (ASEs) and mechanisms behind the transmittance of sound in a metallic micro-cavity acoustic black hole (ABH) structure with an abrupt cross-section and examines the sound field flow characteristics inside the micro-cavity ABH under the sound excitation, such as the velocity, acceleration and pressure fields. And the sound transmission mechanisms are characterized by the ASEs which can be obtained by solving Navier–Stokes equations. The numerical results show that the sharp increase in the velocity and acceleration at the ABH tip position is the main reason for the focusing of the sound energy. And the dramatic increase in the tip cross-section reduces the acoustic streaming velocity, which is the main reason for the attenuation of the sound energy. Additionally, the thermoviscous effect of the acoustic boundary layer can also dissipate the low-frequency sound energy. The sound insulation experiment shows that the proposed micro-cavity ABH structure has a sound transmission loss (STL) of over 15 dB in the low-frequency regime. This research reveals the mechanisms of the ASE's work on the sound transmission properties of the micro-cavity ABH and provides new insight into low-frequency sound wave suppression. The ABH structure proposed in this paper has excellent strength, bearing capacity and long lifecycle, so it can be applied in the construction industry through its integrated design of structure and performance. [ABSTRACT FROM AUTHOR]

Metallic yielding devices have been widely used for improving seismic performance of buildings. However, metallic dampers currently in use are often attached to structural systems through brace components, potentially causing conflicts with architectural requirements. In this study, a metallic damper that utilizes the angular deformation generated at the beam‐column connection under lateral loads is proposed. The seismic input energy can be dissipated through inelastic deformations of hyperbolic‐shaped steel bars. Firstly, this paper introduces the configuration and design concept of the newly proposed rotation‐based metallic damper (RMD). Then, in order to investigate the hysteretic behavior and failure modes of the proposed devices, a total of twelve RMD specimens were fabricated, and quasistatic tests were conducted. Subsequently, the influences of physical characteristics associated with hyperbolic‐shaped steel bars on the energy dissipation performance of RMD were studied. Finally, finite element analysis was conducted based on the detailed models of RMD specimens, and the results showed a good agreement with the experimental data. The results demonstrate that the RMD exhibits a sound energy dissipation capacity. It is replaceable and flexible in architectural arrangements due to its low space requirements, which is friendly in engineering practice. [ABSTRACT FROM AUTHOR]

Sound can exert forces on objects of any material and shape. This has made the contactless manipulation of objects by intense ultrasound a fascinating area of research with wide-ranging applications. While much is understood for acoustic forcing of individual objects, sound-mediated interactions among multiple objects at close range gives rise to a rich set of structures and dynamics that are less explored and have been emerging as a frontier for research. We introduce the basic mechanisms giving rise to sound-mediated interactions among rigid as well as deformable particles, focusing on the regime where the particles' size and spacing are much smaller than the sound wavelength. The interplay of secondary acoustic scattering, Bjerknes forces, and micro-streaming is discussed and the role of particle shape is highlighted. Furthermore, we present recent advances in characterizing non-conservative and non-pairwise additive contributions to the particle interactions, along with instabilities and active fluctuations. These excitations emerge at sufficiently strong sound energy density and can act as an effective temperature in otherwise athermal systems. [ABSTRACT FROM AUTHOR]

The Strait of Hormuz, as a crucial link between the Persian Gulf and the Gulf of Oman, exhibits complex and distinct currents that are influenced by the connection of saline waters from the Persian Gulf and the Gulf of Oman. These currents contribute to the formation of seasonal eddies, influencing the deviation and dissipation of sound energy and causing notable changes in sound speed profiles in the region. This study utilized the ROMS 3D software to simulate variable circulation patterns and the development of mesoscale eddies in the Persian Gulf based on data from 2009. The simulations, conducted with a resolution of approximately 3 km and 16 layers at the sigma level, revealed a correlation between fluctuations in wind stress and variations in flows within the Strait of Hormuz. The exchange circulation induced by wind stress led to local instability and the formation of cyclonic eddies, particularly prominent in August. Following the simulations, acoustic modeling was performed using parabolic equations and the RAMGEO model. The study focused on frequencies of 100 and 500 Hz, covering a transmission range of 10 km at six stations within the Strait of Hormuz. Sound sources were strategically placed in the surface layer, thermocline layer, and homogeneous layer near the seabed. Analysis of the two-dimensional outputs of transmission loss indicated that the position of the sound source near the seabed had the most significant impact, followed by the thermocline layer and the surface layer. [ABSTRACT FROM AUTHOR]

Determining precipitation as solid (snow) or liquid (rain) phase is crucial for remote sensing of precipitation. Most phase classification methods rely on near‐surface temperatures. Further attempts to incorporate atmospheric information aloft only achieved mixed level of success, particularly for precipitation with temperature inversion. In our study, we developed a phase classification scheme based on the upper‐level melting energy (ME) and refreezing energy (RE), which is proportional to the area enclosed by the temperature profile and the 0°C isotherm. We performed least squares fitting and linear discriminant analysis to derive phase separation functions using observed surface and sounding data in North America. We provided separation functions for snow conditional probabilities ranging from 30% to 80% for various applications. Compared to a previously published (Probsnow) method, our energy method achieved comparable performance for Type 1 soundings with one near‐surface melting layer, and significantly improves the phase classification scores for Type 2 soundings with an aloft melting layer and a near‐surface refreezing layer. We innovatively combined surface ice‐bulb temperature with the ratio between the ME and RE to represent Type 2 profiles. For Type 2 soundings, our energy method improves the Heidke skill score (HSS) from 0.25 to 0.47 and reduces false alarm rate (FAR) by 0.47 compared to the Probsnow method for 50% threshold. By applying the physically based method, we improved accuracy and HSS, and reduced FAR for more than two thirds of the evaluation stations across the North America. Finally, we tested the application of the new method in satellite snowfall retrievals. Plain Language Summary: In this study, we developed a method to determine whether precipitation is in the form of snow or rain, which is important for weather forecast, modeling, and snowfall measurements with radar. We used atmospheric melting and refreezing energy to represent the physical process that falling precipitation undergoes. Two types of atmosphere structures were considered: melting near the surface (Type 1), and melting‐refreezing profiles (Type 2). Compared to a previous method, we achieved comparable performance for the Type 1 soundings, and achieved major improvements for the Type 2 soundings, where the process of melting and refreezing was not well‐represented by previous methods. Our new method was tested in North America and showed improvements in most stations. The improvements in phase prediction for Type 2 soundings contribute significantly to the overall phase classification for most stations in the North America. Finally, we tested our method for satellite snowfall retrievals. For future applications, we offer different separation functions for various thresholds of the conditional probability of snow to meet different prediction needs. Key Points: We developed a physically based phase classification scheme for two typical types of soundings by incorporating the atmospheric energyWe greatly improved phase prediction for Type 2 sounding, which features a melt‐and‐refreeze process poorly represented by prior methodsWe evaluated the phase classification with a 50% snow probability threshold for North America stations and observed prominent improvements [ABSTRACT FROM AUTHOR]

The necessity of renewable energy is indispensable. Nowadays, researchers focus on converting waste or solar heat into advantageous energy, such as electric energy, using thermoacoustic scientific knowledge. The thermoacoustic machine converts the heat energy into sound energy and conversely. Then, using a linear alternator, it converts into electric energy. In this study, we focus on the construction and testing of small-scale thermoacoustic electricity generators with different heating temperatures. The heat is converted into acoustic energy employing the thermoacoustic engine, and the acoustic energy is converted into electrical energy using the linear alternator. In this investigation, the heating power varies from 226-389 W. The result shows that 32.2 mW of electricity was found as the thermal power at 389 W. Moreover, the onset heating temperature span is 316 °C. [ABSTRACT FROM AUTHOR]

In this paper, we study the gravitational waves of holographic QCD phase transition with hyperscaling violation. We consider an Einstein–Maxwell Dilaton background and discuss the confinement–deconfinement phase transition between thermally charged AdS and AdS black holes. We find that hyperscaling violation reduces the phase transition temperature. In a further study, we discuss the effect of hyperscaling violation on the GW spectrum. We found that the hyperscaling violation exponent suppresses the peak frequency of the total GW spectrum. Moreover, the results of the GW spectrum may be detected by IPTA, SKA, BBO, and NANOGrav. We also find that the hyperscaling violation exponent suppresses the peak frequency of the bubble-collision spectrum h 2 Ω e n v . Hyperscaling violation enhances the energy densities of the sound wave spectrum h 2 Ω s w and the MHD turbulence spectrum h 2 Ω t u r b . The total GW spectrum is dominated by the contribution of the bubble collision in runaway bubbles case. [ABSTRACT FROM AUTHOR]

Simulating the acoustic field excited by pulse sound sources holds significant practical value in computational ocean acoustics. Two primary methods exist for modeling underwater acoustic propagation in the time domain: the Fourier synthesis technique based on frequency decomposition and the time-domain underwater acoustic propagation model (TD-UAPM). TD-UAPMs solve the wave equation in the time domain without requiring frequency decomposition, providing a more intuitive explanation of the physical process of sound energy propagation over time. However, time-stepping numerical methods can accumulate numerical errors, making it crucial to improve the algorithm's accuracy for TD-UAPMs. Herein, the time-domain wavenumber integration model SPARC was improved by replacing the second-order finite element method (FEM) with the high-order accuracy finite difference method (FDM). Furthermore, the matched interface and boundary (MIB) method was used to process the seabed more accurately. The improved model was validated using three classic underwater acoustic benchmarks. By comparing the acoustic solutions obtained using the FDM and the FEM, it is evident that the improved model requires fewer grid points while maintaining the same level of accuracy, leading to lower computational costs and faster processing compared to the original model. [ABSTRACT FROM AUTHOR]

This study examines the determinants of modern cooking fuel choices in Korea. The ordered probit model is estimated using an extensive online survey of Korean household energy consumers. Our empirical results showed that age, gender, and education are significant determinants of modern cooking fuel choices among the socioeconomic demographic variables: females, older people, and highly educated people are more likely to prefer electricity. Also, electricity is more likely to be preferred over natural gas by people who have a higher preference for district heating. Two psychological factors significantly influence cooking fuel choices. People whose behaviors are environment-friendly and people who are more health-conscious are more likely to prefer electricity over natural gas or propane. There are three important insights into the cooking fuel transition toward electricity. First, as interest in health and climate change has significantly increased in recent years in Korea, it may stimulate the transition from natural gas or propane to electricity. Second, electrification of cooking methods will be beneficial for the environment if electricity generation becomes less carbon-intensive. Since electricity in Korea is mainly generated by fossil fuels, it is crucial to implement more aggressive policies toward renewable sources in the energy mix for electricity generation. Third, the public should better understand why this problem cannot be overlooked because the energy mix is important in mitigating climate change. The better the people understand the exact relationship between energy consumption and pollutant emissions, the more effective and environmentally sound will the energy mix policy become. [ABSTRACT FROM AUTHOR]

In the present study, poling−free PLLA/VB2 piezoelectric composites are fabricated to achieve synchronous sound recognition and energy harvesting. The addition of VB2 can interact with PLLA by intermolecular hydrogen bonding, inducing the dipole orientation of C=O in PLLA. Meanwhile, VB2 can promote crystallization of PLLA through heterogeneous nucleation. The combination of the two strategies significantly improves the piezoelectric performance of PLLA/VB2 composites. The PLLA/VB2 can detect the sound frequency with an accuracy of 0.1% in the range of 0–20 kHz to recognize characteristic sounds from a specific source. PLLA/VB2 can also convert sound into electrical energy synchronously with an energy density of 0.2 W/cm−3 to power up LEDs. Therefore, PLLA/VB2 shows great potential in the field of information and energy synchronous collection. [ABSTRACT FROM AUTHOR]

Topological acoustics is a rapidly developing field due to its fascinating topological properties in artificial metamaterials. However, the topological crystals are generally composed of coupled waveguides or resonant cavities, which often leads to fixed excitation positions and excessive structure size, so making them difficult to fabricate and apply in real life. In this work, we proposed an ingenious method to manipulate the coupling between resonant units, which takes advantage of the opening direction of the split-multiple-cavity resonator that can be easily adjusted. Based on this structure, a higher-order topological corner state was observed in both simulations and experiments. More interestingly, the sound energy for the corner state is enhanced and can be excited from outside with a point source at an arbitrary location. This peculiar topological phenomenon may find many applications in sound signal acquisition, transmission, and processing. [ABSTRACT FROM AUTHOR]

Since the development of industry, sound absorption and noise reduction have gradually become an urgent problem to be solved. Lightweight polymer film materials are very effective in response to sound waves, and sound waves can easily cause vibration of the film, which can convert sound energy into vibration and film friction to achieve sound absorption. The application conditions of the film material are very harsh, that is, a support body is required to fix the film and the film needs to be tensioned. The film is very thin and easy to damage. The idea of this research is to transform the film into a bubble structure and use a large number of film bubbles to form a cavity structure material. As a unit of the sound absorption structure, bubbles can avoid damage to the film. In this paper, commercial polyvinyl chloride film bubble materials are used to prepare two kinds of film multicavity structure materials, and the sound absorption performance of this film multicavity structure material is studied. The research results show that this film multicavity structure material has very excellent broadband sound absorption performance, which changes the narrow band sound absorption properties of the usual film single cavity. The average sound absorption coefficient can reach 0.84 in frequency range from 500 Hz to 6400 Hz. This structural material has a single peak sound absorption curve at the middle and low frequency bands, which is the characteristic of resonance sound absorption. And at the middle and high frequency bands, it exhibits the characteristics of broadband sound absorption. The film multicavity structure material has both cavity sound absorption and broadband sound absorption characteristics. [ABSTRACT FROM AUTHOR]

The membrane-type structure that can achieve excellent sound insulation characteristics under lightweight conditions is widely concerned, but it generally involves a small mass block attached to a thin membrane. Although this kind of design can obtain better acoustic insulation performance, the mass block will cause installation and manufacturing issues in industrial applications. This paper presents a multilayer honeycomb membrane-type acoustic metamaterial with an interlayer structure. Similar to the mass block, the interlayer structure makes less sound energy transmitted by varying the eigenmode characteristics of the membrane. Considering the integrated design of the interlayer structure, the issues of installation and manufacturing are solved and the sound transmission loss is enhanced on the fixed overall dimension and small additional mass. The results indicate that the design of interlayer structures can break the bottleneck of ultrathin and lightweight requirements. Meanwhile, the symmetry of interlayer position can lead to the shift in transmission loss valley to a higher frequency, achieving high sound insulation in a wide frequency range. [ABSTRACT FROM AUTHOR]

The swim bladder in some teleost fish functions to transfer the sound energy of acoustic stimuli to the inner ears. This study uses the auditory evoked potential tests, micro-computed tomography scanning, reconstruction, and numerical modeling to assess the contribution of the swim bladder to hearing in crucian carp (Carassius carassius). The auditory evoked potential results show that, at the tested frequency range, the audiogram of fish with an intact swim bladder linearly increases, ranging from 100 to 600 Hz. Over this frequency, the sound pressure thresholds have a local lowest value at 800 Hz. The mean auditory threshold of fish with an intact swim bladder is lower than that of fish with a deflated swim bladder by 0.8–20.7 dB. Furthermore, numerical simulations show that the received pressure of the intact swim bladders occurs at a mean peak frequency of 826 ± 13.6 Hz, and no peak response is found in the deflated swim bladders. The increased sensitivity of reception in sound pressure and acceleration are 34.4 dB re 1 μPa and 40.3 dB re 1 m·s−2 at the natural frequency of swim bladder, respectively. Both electrophysiological measurement and numerical simulation results show that the swim bladder can potentially extend hearing bandwidth and further enhance auditory sensitivity in C. carassius. [ABSTRACT FROM AUTHOR]

The anechoic coating capable of absorbing sound energy in low frequencies within broadband is essential to conceal underwater vehicles. However, the geometric deformation and modification of mechanical parameters under hydrostatic pressure affect the prediction of absorption performance in deep water environments. An anechoic coating embedded with tandem resonant voids is proposed in this work to achieve quasi-perfect low-frequency and broadband absorption. The analytical method based on the effective medium approach and numerical simulation are performed to estimate the effects of hydrostatic pressure on sound absorption. When additionally considering the dynamic mechanical parameters of the compressed viscoelastic medium, the original absorption humps in low frequencies are inclined to higher band, accompanied by the expanded absorption bandwidth. Then, the tandem coating specimen is measured in a water-filled impedance tube. The experimental spectra are consistent with the analytical and numerical results under various hydrostatic pressures, demonstrating the efficient absorption (α > 0.7) in broadband low frequencies via ordinary pressure. At the same time, the absorption spectrum under higher hydrostatic pressures is also verified in the tube. Consequently, this work paves the way for a broadband low-frequency underwater absorber design and provides an efficient method to characterize the low-frequency and broadband absorption from the coupled resonant coatings in deep water environments. [ABSTRACT FROM AUTHOR]

Sound Event Localization and Detection (SELD) is the task of spatial and temporal localization of various sound events and their classification. Commonly, multitask models are used to perform SELD. In this work, a deep learning network model named channel-wise 'FusionNet' is designed to perform the SELD task. The novel fusion layer is introduced into the regular Deep Neural Network (DNN), where the input is fed channel-wise, and the outputs of all channels are fused to form a new feature representation. The key contribution of this work is the neural network model which helps to retain the channel-wise information from the multichannel input along with the spatial and temporal information. The proposed network utilizes separable convolution blocks in the convolution layers, therefore, the complexity of the model is low in terms of both time and space. The features used as input are Mel-band energies for Sound Event Detection (SED) and intensity vectors for the Direction-of-Arrival (DOA) estimation. The proposed network's fusion layer provides a better representation of features for both SED and DOA estimation tasks. Experiments are performed on the recordings of the First-order Ambisonic (FOA) array format of the TAU-NIGENS Spatial Sound Events 2020 dataset. An improved performance is achieved in terms of Error Rate (ER), DOA error, and Frame Recall (FR) has been observed in comparison to the state-of-the-art SELD systems. [ABSTRACT FROM AUTHOR]

The genus Aplastodiscus (Hylidae) is widely distributed in the Atlantic Forest of Brazil and adjacent Argentina, and a single species inhabits the Cerrado in Central Brazil. The genus comprises 16 species included in 4 species groups. The A. albosignatus species group contains 6 described species, as well as two candidate species referred to as Aplastodiscus sp. 5 and Aplastodiscus sp. 6 in previous studies. Here we name and describe Aplastodiscus sp. 6, based on morphology, DNA sequences, and vocalizations. The new species is known only from the northern sector of the Mantiqueira Mountain Range and can be distinguished morphologically from most congeneric species based on body size, iris color pattern, and cloacal ornamentation. The new species is distinguished from its sister species A. leucopygius by its vocalization. The species of the A. albosignatus group share a conserved external morphology and most of the morphological characters traditionally included in their diagnoses failed to distinguish them. In contrast, advertisement call traits, such as call duration, call envelope, and distribution of sound energy in the harmonic series, were informative in Aplastodiscus species discrimination. [ABSTRACT FROM AUTHOR]

Noise from elevated railway bridges in urban areas has been causing severe environmental issues. To find the peak frequency of sound energy and thus develop targeted countermeasures for noise mitigation, policymakers need a better understanding of the noise characteristics of urban railway bridges during train passage. This study approaches this issue by combining transient dynamic analyses and acoustic finite element simulation. Our frequency characteristic analysis focused on two primary noise sources: wheel-rail noise and bridge-borne noise. We built a spatial noise model that predicts the radiated noise of urban railway bridges in both the active and planning stages. The results show that the wheel-rail noise peaked at 800 Hz, 1600 Hz, and 3150 Hz, while the bridge-borne noise peaked at 40 Hz, 50 Hz, 80 Hz, and 125 Hz. The validation results demonstrated that the developed noise spatial prediction model extended well to similar urban railway bridges. [ABSTRACT FROM AUTHOR]

Purpose: This paper introduces a novel analysis model for a sound energy harvester that goes beyond the traditional methods based on piezoelectric or electromagnetic effects. The proposed model utilizes both piezoelectric and flexoelectric effects and consists of a flexoelectric vibrating plate and a phononic crystal with defect points to enhance the power of sound energy harvesting. Methods: Using plane wave expansion and supercell methods, this paper obtains the defect band frequencies and corresponding acoustic pressure distribution of the defective state phononic crystal. By applying the Hamiltonian principle, the electromechanical control equations for the double-layer flexoelectric plate are derived. The Galerkin method is employed to solve these equations, providing an approximate closed-form solution for voltage output. Finite-element simulations validate the theoretical results. Conclusion: The study reveals a significant enhancement (3.66 times) in voltage output for the sound energy harvester at the micro-nano-scale through the combined effects of flexoelectricity and piezoelectricity. The presence of defect state phononic crystal results in 4.24-fold, 11.60-fold, and 2.55-fold increases in voltage output, power output, and energy conversion efficiency, respectively, for the flexoelectric sound energy harvester. Additionally, optimal laying schemes and load resistance for the flexoelectric layer are provided. [ABSTRACT FROM AUTHOR]

Chuprov's interference invariant (II) well describes the properties of a sound field in shallow water. However, the question of how applicable Chuprov's II concept is to deep water, where the patterns of sound field decay with distance are more complex has been insufficiently studied. Therefore, the authors studied the II properties in the near and far fields of acoustic illumination, as well as in the shadow zone. A new definition of the invariant was proposed and studied, and its characteristics were compared with Chuprov's II as a function of distance, reception and emission depths, and summer or winter propagation conditions. The new invariant is called the phase-energy invariant (PEI), since orthogonal components of the phase gradient are used to describe the spatial sound energy distribution. The stability of the new invariant, its independence on different influencing factors, and its natural change with distance from zero to one are shown. It has been established that in winter conditions, at almost all distances, the PEI is equal to unity, and the II does not have stable values and varies jumpwise over a very wide range. In summer conditions, in the shadow zone, with increasing distance, the PEI increases, just like the II, from close to zero to one. In the near and far fields of acoustic illumination, the PEI is approximately equal to unity, and the II in these zones, both in summer and winter, is characterized by unlimited oscillations, caused by division by a value close to zero. It is shown that the definition of PEI is valid both in single-mode waveguides and in free unbounded space with a dispersive medium. [ABSTRACT FROM AUTHOR]

Due to their high heat transfer capabilities, energy absorption and sound insulation characteristics, lattice structures are used in different industries, especially in aviation, automotive and biomedical industries. Different process and geometric parameters are effective on these capabilities of lattice structures. It is well known that the use of suitable lattice structure together with appropriate process and geometric parameters in different industrial applications increases the efficiency obtained as a result of the application. This experimental study focuses on investigating the effect of lattice structure type, build direction and volume fraction on distortion, surface roughness and wall thickness deviation of lattice structures based on Taguchi design of experiment. Laser powder bed fusion process and CoCrMo material were used for production. The effect of each parameter on distortion, surface roughness and wall thickness deviation, and optimum parameter set were found by analysis of variance (ANOVA) method. The optimum parameter set for surface roughness was determined as diamond lattice structure, 0.2 volume fraction and 90o build orientation. On the other hand, the optimum parameter set for wall thickness deviation was determined as gyroid lattice structure, 0.4 volume fraction and 45o build orientation. [ABSTRACT FROM AUTHOR]

The paper discusses the cosmological model with an interaction between dynamical quintessence dark energy and cold dark matter. Evolution of the dark energy equation of state parameter is defined by the dark energy adiabatic sound speed and the dark sector interaction parameter, which must be a more physically correct model then the one previously used, in which this evolution was determined by some fixed dependence on the scale factor. The constraints on the interaction parameter and other parameters of the model were obtained using the cosmic microwave background, baryon acoustic oscillations and the supernova SN Ia data. [ABSTRACT FROM AUTHOR]

Mobile and wearable devices are now the main part of our lives. The power consumed by these devices is usually in the range of μW or mW. Due to the requirement of periodic recharging, this work tries to present an economic renewable energy harvesting source for the process of charging. In this paper, authors exploit a huge amount of energy dissipated daily in the form of loud noise through streets up to 85 dB to generate a sufficient rate of energy to recharge the lithium batteries of wearable and mobile devices (more than 4.01 V). The piezoelectric model 7BB-27-4 was used in this work through a proposed design circuit. Suitable software was used to simulate the design. In comparison to previous research findings, the authors' findings are sufficiently satisfactory. [ABSTRACT FROM AUTHOR]

We describe studies of the interaction of a pulsed Nd:YAG laser with bovine serum albumin (BSA) solution (i.e., S0) and S0 containing gold nanourchin (GNU) (i.e., S1: S0 + 0.1 ml GNU) using combined photoacoustic (PA) and probe beam deflection (PBD) techniques. The changes in absorbance and chemical bonds are studied by UV–Vis and near-FTIR spectroscopy. The results showed a decrease in absorbance of the bio-plasmonic solution, which further decreased by increasing the concentration. The PA pressure increased with fluence in the order of GNU > S0 > S1, and all exhibited a non-linear response at ≈9.5 J cm−2 and reached a maximum at 12.5 J cm−2. No PBD was observed in S0 indicating the role of GNU in producing the heating effect. ∂n/∂T increased in the order of S2 > S1 > S0, respectively, where S2 is (S0 + 0.2 ml GNU). The absorbance of S0 and S1 increased after heating due to protein denaturation. For S1, surface-enhanced FTIR showed an increase in the intensity of most bands between 6320 and 6630 cm−1, and the band at 5264 cm−1, which likely corresponds to β-sheet structure, significantly diminished after heating. The collapse of cavitation and plasma shock waves produced significant acoustic transients, hence some photomechanical effects. The acoustic energy released after the collapse of bubbles at 1.8 and 12.5 J cm−2 was calculated to be ≈140 μJ and 7 mJ, respectively, corresponding to 4% and 28% of the input optical energy being converted to sound energy in the early phase of the expansion. [ABSTRACT FROM AUTHOR]

A high-sensitivity liquid concentration-sensing structure based on a phoxonic crystal slot nanobeam with gradient cavities is presented and its sensing properties are investigated using the finite element method. The proposed sensing structure, which can be made from either isotropic or anisotropic materials, can have excellent sensing properties that are designed via geometric optimization. We investigate the influences of various solution concentrations on electromagnetic and elastic wave transmission spectra. The results demonstrate that the introduction of gradient cavities can enable the system to avoid lattice mutation and reduce energy loss, thereby concentrating light and sound energy in the slot and holes, enhancing interactions between the electromagnetic and elastic waves, and improving sensitivity. It is worth noting that the sensing characteristics are related to the electric field distribution in the light sensor. That is, the sensitivity is better when more electric energy is distributed in the liquid-filled slot and holes. The sensitivity can reach 238.1 nm/RIU. The acoustic sensing properties are related to the solid–liquid interaction. This is especially true for the modal sensing characteristics, where the acoustic energy is concentrated on the solid–liquid interface. Therefore, greater interaction strength implies better sensitivity. The acoustic sensitivity can reach 3167 kHz/ms−1. The proposed structure provides acoustic and optical cross-checks for different types of solutions. This helps us to improve sensing accuracy and reduce sensing uncertainty. [ABSTRACT FROM AUTHOR]

To make the sound absorber easy to fabricate and convenient for practical application, a modular composable acoustic metamaterial with multiple nonunique chambers (MCAM–MNCs) was proposed and investigated, which was divided into a front panel with the same perforated apertures and a rear chamber with a nonunique grouped cavity. Through the acoustic finite element simulation, the parametric studies of the diameter of aperture d, depth of chamber T0, and thickness of panel t0 were conducted, which could tune the sound absorption performances of MCAM–MNCs–1 and MCAM–MNCs–2 for the expected noise reduction effect. The effective sound absorption band of MCAM–MNCs–1 was 556 Hz (773–1329 Hz), 456 Hz (646–1102 Hz), and 387 Hz (564–951 Hz) for T = 30 mm, T = 40 mm, and T = 50 mm, respectively, and the corresponding average sound absorption coefficient was 0.8696, 0.8854, and 0.8916, accordingly, which exhibited excellent noise attenuation performance. The sound absorption mechanism of MCAM–MNCs was investigated by the distributions of the total sound energy density (TSED). The components used to assemble the MCAM–MNCs sample were fabricated by additive manufacturing, and its actual sound absorption coefficients were tested according to the transfer matrix method, which demonstrated its feasibility and promoted its actual application. [ABSTRACT FROM AUTHOR]

Mechanical energy in the form of ultrasound and protein complexes intuitively have been considered as two distinct unrelated topics. However, in the past few years, increasingly more attention has been paid to the ability of ultrasound to induce chemical modifications on protein molecules that further change protein–protein interaction and protein self‐assembling behavior. Despite efforts to decipher the exact structure and the behavior‐modifying effects of ultrasound on proteins, our current understanding of these aspects remains limited. The limitation arises from the complexity of both phenomena. Ultrasound produces multiple chemical, mechanical, and thermal effects in aqueous media. Proteins are dynamic molecules with diverse complexation mechanisms. This review provides an exhaustive analysis of the progress made in better understanding the role of ultrasound in protein complexation. It describes in detail how ultrasound affects an aqueous environment and the impact of each effect separately and when combined with the protein structure and fold, the protein–protein interaction, and finally the protein self‐assembly. It specifically focuses on modifying role of ultrasound in amyloid self‐assembly, where the latter is associated with multiple neurodegenerative disorders. [ABSTRACT FROM AUTHOR]

In this paper, the acoustic signal of the underwater explosion was taken as the main research object, and the mechanical and acoustic characteristics of the underwater explosion were studied by combining theoretical research with simulation, the propagation law of shock wave and the acoustic characteristics of explosion signal with different explosion depth and charge were obtained. The results show that the underwater explosion has strong acoustic power, high sound pressure level, wide frequency coverage of explosion acoustic signal. In low frequency band, the acoustic power level decays rapidly with the increase of frequency, and its acoustic energy is very high; in higher frequency band, the acoustic power level decays slowly, and its sound energy is relatively low; bubble pulsation has a great influence on the energy distribution of acoustic power level, and the more bubble pulsation times, the greater the proportion of low-frequency energy. The research results of this article can provide a theoretical basis for the research of fuze anti-interference. [ABSTRACT FROM AUTHOR]

The acoustic absorption characteristics of anechoic coatings attached to the surface of underwater vehicles are closely related to their acoustic stealth. Owing to the essential property of local resonance, the narrow sound-absorption band cannot meet the underwater broadband sound absorption requirements. To this end, a multi-mechanism synergistic composite acoustic structure (MMSC−AS) was designed according to the integration of multiple acoustic dissipation mechanisms in this paper. Then, the acoustical calculation model for MMSC−AS was developed by using the graded finite element method (G-FEM), and the feasibility and the correctness of the established acoustical calculation model were verified. The underwater sound absorption behaviors of MMSC−AS were studied, and the optimization of the sound absorption characteristics of the MMSC−AS was also carried out. The results indicated that the calculation accuracy of the G-FEM was better than that of the FEM under the condition of the same mesh elements. Moreover, there were many sound wave regulation mechanisms in the MMSC−AS, and the synergy between the mechanisms enriched the mode of sound acoustic energy dissipation, which could widen the absorption band with effect. This study provides theoretical and technical basis for breaking through the challenge of low-frequency and broadband acoustic structure design of underwater vehicles. [ABSTRACT FROM AUTHOR]

Efficient acoustic communication across the water–air interface has always been expected in the field of ocean exploration. However, the existing research works are mainly concentrated on the narrow-band transmission based on resonance, which greatly limits the transmission capacity and efficiency. Here, we combined air-based and water-based metafluids to realize an exponential gradient impedance matching layer for broadband water–air sound transmission. By cooperatively adjusting the sound velocity and thickness in the matching layers, we modulated the required acoustic parameters of each layer into a reasonable range, which can be conveniently achieved by the proposed metafluids. A matching layer sample was constructed and validated in a water tank. Experimental results show that the proposed matching layer can achieve an average sound energy transmission enhancement above 16.7 dB from 880 to 1760 Hz across the water–air interface. A water–air acoustic communication scene was further experimentally demonstrated through transmitting a multicolor picture from air to water, which shows extremely high communication capacity and accuracy. Our work is promising for more applications based on water-air transmission and opens an avenue to the design and implementation of the extreme impedance matching case. [ABSTRACT FROM AUTHOR]

A space‐shift phase‐coherent cancellation acoustic metasurface is developed, which can achieve broadband low‐frequency sound absorption via ultra‐thin integrated structure composed of multiple units with weak absorption capability. Through a space‐shift design of the channel length, the large‐size required in the thickness direction for low‐frequency absorption is transferred into an extremely ultra‐thin space layer. The units with gradient channel length are compactly arranged in an ultra‐thin layer through space folding, a coplanar sound absorption metasurface component with working bandwidth exceeding an octave and thickness of only λ/25 to λ/57 is obtained. As the construction of a special double‐hole "bridge" layout, even if the elements are sparsely distributed, strong coupling interactions between the units can sustain. When a certain local phase relationship is satisfied, the coherent cancellation of sound energy can be achieved, so as to reduce the sound reflection and scattering, and enhance the absorption performance. Therefore, from the perspective of phase relationship among units, the present work provides more clear physical image and intuitive theoretical explanation for achieving excellent broadband sound absorption through parallel superposition of multiple units with weak absorption capability. The proposed ultra‐thin sound absorbing metasurface can satisfy the thickness limitations and absorption performance requirements in most equipment. [ABSTRACT FROM AUTHOR]

The frequency range audible to humans can extend from 20 Hz to 20 kHz, but only a portion of this range—the lower end up to 8 kHz—has been systematically explored because extended high-frequency (EHF) information above this low range has been considered unnecessary for speech comprehension. This special issue presents a collection of research studies exploring the presence of EHF information in the acoustic signal and its perceptual utility. The papers address the role of EHF hearing in auditory perception, the impact of EHF hearing loss on speech perception in specific populations and occupational settings, the importance of EHF in speech recognition and in providing speaker-related information, the utility of acoustic EHF energy in fricative sounds, and ultrasonic vocalizations in mice in relation to human hearing. Collectively, the research findings offer new insights and converge in showing that not only is EHF energy present in the speech spectrum, but listeners can utilize EHF cues in speech processing and recognition, and EHF hearing loss has detrimental effects on perception of speech and non-speech sounds. Together, this collection challenges the conventional notion that EHF information has minimal functional significance. [ABSTRACT FROM AUTHOR]

Traditional energy sources are progressively moving toward depletion, resulting in a growing scarcity of energy driven by demand. In contrast, the realm of acoustic energy harvesting remains relatively unexplored, particularly within enclosed environments. In this work, we proposed a novel piezoelectric energy harvesting system, enhanced with various circuit components such as operational amplifiers and voltage quadruplers. Piezoelectric transducers are a type of electro acoustic transducer that convert the electrical charges triggered by some forms of mechanical vibrations like sound into energy. The core of the system relies on the utilization of piezoelectric technology to transform untapped sound energy into electrical energy. This innovative energy harvesting approach holds the promise of enhancing the quality of sound conditioning within enclosed spaces. Furthermore, the proposed methodology serves to mitigate the risk of noise-induced trauma, which has the potential to cause detrimental long-term effects. It is also cascade into a transformative trajectory, offering sustainable energy harvesting avenues and fostering the amelioration of soundscapes within the tapestry of confined environs. The observations made increased the efficiency of the system by 6%, and the range is increased four times. In our experiments, we obtained a higher voltage of around 12 V for a theater setup with sound levels between 70 and 90 dB, which surpasses the existing results. [ABSTRACT FROM AUTHOR]

It has been reported that the properties of a foam-based sandwich panel can be enhanced by incorporating nanoclay into the facesheet or foam core. In this study, an attempt was made to disperse nanoclay into the epoxy adhesive so as to bond the facesheet with the core. The sandwich panel in this study was fabricated using a basalt/epoxy laminate as the facesheet and polyvinyl chloride foam as the core material. The characterisation results through flexural and quasi-static indentation tests revealed that the infusion of nanoclay led to an increase of up to 34% in the bending strength, 51% in the core shear strength, and 72% in energy absorption. In addition, the nanoclay-reinforced sandwich panel showed a slightly higher sound absorption coefficient than the control specimen without nanoclay. Another interesting observation from the flexural and quasi-static indentation tests was that the addition of nanoclay also influenced the failure behaviour and the size of the damaged area. The superior energy and sound absorption characteristics make the foam-based sandwich panel a potential material for structural applications requiring acoustic insulation. [ABSTRACT FROM AUTHOR]

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A theoretical model and a finite element (FE) model are proposed to evaluate the effect of high temperature on the sound absorption performance of cylindrically perforated porous materials. The theoretical model is established by applying the double porosity theory, in which the perforated porous material is considered as a combination of the porous material matrix and the cylindrical perforation. The FE model is constructed using the pressure acoustics module of the COMSOL Multiphysics software to verify the theoretical model. In these two models, the temperature effect is accounted for by applying the temperature-dependent physical parameters of the air in the porous material. Several representative examples show that the results obtained by the theoretical model agree well with those obtained by the FE model, and the sound absorption peak moves to higher frequencies as the temperature rises. The analysis of the propagation and dissipation of sound energy at different temperatures shows that the increase in temperature can prevent sound from entering the porous medium, thereby delaying the appearance of the absorption peak along the frequency axis. The perforated porous materials exhibit higher sound absorption performance than traditional homogeneous porous materials and, therefore, have enhanced high-temperature sound absorption potential. [ABSTRACT FROM AUTHOR]

Recently, the concept of a higher-order topological insulator has prompted increasing scientific interest in achieving the lower-dimensional boundary states. Among them, the zero-dimensional topological corner states in 2D/3D stereo acoustic systems are sustained in the second-/third-order topological insulators. However, the wavelength-scale unit size limits the application potential of corner states in acoustics, and the acoustic third-order topological insulator with a subwavelength unit cell is in urgent need to be proposed. Here, we use sub-wavelength acoustic waveguide networks to construct sonic lattices and configure the waveguide size to modulate the coupling strength in both 2D and 3D systems. The topological corner mode of second-/third-order topological insulators appears when the intra-cell coupling strength is weaker than the inter-cell one. Through calculating the eigenfrequencies and simulating the intensity response, the existence of a topological 2D surface, 1D hinge, and 0D corner states is ascertained. We demonstrate that the proposed topological acoustic corner mode may have potential applications in realizing the sound confinement and energy harvesting in both 2D and 3D systems. [ABSTRACT FROM AUTHOR]