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The intrigue of waves on periodic lattices and gratings has resonated with physicists and mathematicians alike for decades. In-depth analysis has been devoted to the seemingly simplest array system: a one-dimensionally periodic lattice of two-dimensional scatterers embedded in a dispersionless medium governed by the Helmholtz equation. We investigate such a system and experimentally confirm the existence of a new class of generalised Rayleigh–Bloch waves that have been recently theorised to exist in classical wave regimes, without the need for resonant scatterers. Airborne acoustics serves as such a regime and we experimentally observe the first generalised Rayleigh–Bloch waves above the first cut-off, i.e., in the radiative regime. We consider radiative acoustic lattice resonances along a diffraction grating and connect them to generalised Rayleigh–Bloch waves by considering both short and long arrays of non-resonant 2D cylindrical Neumann scatterers embedded in air. On short arrays, we observe finite lattice resonances under continuous wave excitation, and on long arrays, we observe propagating Rayleigh–Bloch waves under pulsed excitation. We interpret their existence by considering multiple wave scattering theory and, in doing so, unify differing nomenclatures used to describe waves on infinite periodic and finite arrays and the interpretation of their dispersive properties. The interaction of waves with periodic structures is a feature central to many areas of physics from quantum mechanics to acoustics. Here, the authors numerically and experimentally demonstrate the presence of Rayleigh-Bloch waves in the regime above the first cut-off using acoustic gratings. [ABSTRACT FROM AUTHOR]

The stability of time-dependent compressible linear flows, which are characterized by periodic variations in either their shape or their shear, is investigated. Two novel parametric instabilities are found: an instability that occurs for periodically wobbling elliptic vortices at a number of discrete oscillation frequencies that are proportional to the Mach number and an instability that occurs for all linear flows at various frequencies of the shear oscillation that depend on the Mach number. In addition, the physical mechanism underlying the instabilities is explained in terms of the linear interaction of three waves with time-varying wavevectors that describe the evolution of perturbations: a vorticity wave representing the evolution of incompressible perturbations and two counter-propagating acoustic waves. Elliptical instability occurs because the scale of the acoustic waves decreases exponentially and their wave action is conserved, leading to an exponential increase in the acoustic waves' energies. The instability in shear-varying flows is driven by the interaction between vorticity and the acoustic waves, which couple through the shear and for specific frequencies resonate parametrically, leading to exponential or linear growth. [ABSTRACT FROM AUTHOR]

Novel cellular materials promise a combination of high strength and low specific weight for sustainable and energy‐efficient material design. Inhomogeneities of the materials, such as varying coating thickness, are inherent to the production process but require advanced characterization in order to better understand mechanical properties. Herein, global and local acoustic analysis for nondestructive characterization of local coating thickness on an open‐porous hybrid metal foam system is studied. Experiments and numerical simulations are carried out to evaluate vibration behavior stimulated by a low‐energy impact. The novelty of the work is the use of local excitation and analysis of decay times to determine coating thickness gradients. This qualitative measurement can inform and speed up the material development process due to its simplicity, speed, and low cost. Furthermore, it provides a basis for quality control when scaling up the technology of metal hybrid foams for industrial applications. [ABSTRACT FROM AUTHOR]

Much of Western classical music relies on instruments based on acoustic resonance, which produce harmonic or quasi-harmonic sounds. In contrast, since the mid-twentieth century, popular music has increasingly been produced in recording studios, where it is not bound by the constraints of harmonic sounds. In this study, we use modified MPEG-7 features to explore and characterise the evolution of noise and inharmonicity in popular music since 1961. We place this evolution in the context of other broad categories of music, including Western classical piano music, orchestral music, and musique concrète. We introduce new features that distinguish between inharmonicity caused by noise and that resulting from interactions between discrete partials. Our analysis reveals that the history of popular music since 1961 can be divided into three phases. From 1961 to 1972, inharmonicity in popular music, initially only slightly higher than in orchestral music, increased significantly. Between 1972 and 1986, this rise in inharmonicity was accompanied by an increase in noise, but since 1986, both inharmonicity and noise have moderately decreased. In recent years (up to 2020), popular music has remained much more inharmonic than popular music from the 1960s or orchestral music involving acoustic resonance instruments. However, it has become less noisy, with noise levels comparable to those of orchestral music. We relate these trends to the evolution of music production techniques. In particular, the use of multi-tracking may explain the higher inharmonicity in popular music compared to orchestral music. We illustrate these trends with analyses of key artists and tracks. [ABSTRACT FROM AUTHOR]

Helmholtz resonators flush-mounted in a wall beneath turbulent boundary layer flow are studied by focusing on their flow-induced excitation and effect on the grazing turbulent flow. A particular focus lies on single resonators tuned to the most intense spatio-temporal fluctuations in the near-wall vertical velocity and wall-pressure, residing at a spatial scale of $ \lambda _x^+ \approx 250 $ λ x + ≈ 250 (or temporal scale of $ T^+ \approx 25 $ T + ≈ 25). Resonators are examined in a boundary layer flow at $ Re_\tau \approx 2280 $ R e τ ≈ 2280. Two neck-orifice diameters of $ d^+ \approx 68 $ d + ≈ 68 and 102 are considered, and for each value of $ d^+ $ d + three different resonance frequencies are studied (corresponding to a period of $ T^+ \approx 25 $ T + ≈ 25 , as well as one lower, and one higher, period). The response of the TBL flow is analysed by employing velocity data from hot-wire anemometry and particle image velocimetry measurements. Passive resonance only affects streamwise velocity fluctuations in the region $ y^+ \lesssim 25 $ y + ≲ 25 , while vertical velocity fluctuations due to resonance reach up to $ y^+ \approx 100 $ y + ≈ 100. A narrow-band increase in streamwise turbulence kinetic energy at the resonance scale co-exists with a more than 20% attenuation of lower-frequency energy. Current findings on single resonator cases will aid in the development of passive surfaces with distributed resonators for boundary-layer flow control. [ABSTRACT FROM AUTHOR]

Kunqu Opera, hailed as the "ancestor of all Chinese operas", plays a crucial role in preserving cultural identity and collective memory in the Jiangnan region. This research examines the acoustical traditions of Kunqu. Through expert interviews and thematic analysis, the study explores key acoustic elements, including vocal techniques and musical structures, and their symbolic and emotional impact. Five central themes emerged, including Kunqu's role in collective memory, its function as a cultural symbol, the evolution of its transmission, the emotional resonance of its acoustic elements, and the modern challenges and opportunities for preservation. The findings highlight the importance of maintaining Kunqu's cultural identity within acoustical heritage, while also recognizing the need for innovation in its transmission. This research contributes to the broader discussion on intangible cultural heritage and provides insights into how traditional art forms like Kunqu can be preserved amidst modernization. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) devices combining piezoelectric and magnetostrictive materials have emerged as powerful tools to miniaturize and enhance sensing and communication technologies. This paper examines recent developments in bulk acoustic wave (BAW) and surface acoustic wave (SAW) ME devices, which demonstrate unique capabilities in ultra-sensitive magnetic sensing, compact antennas, and quantum applications. Leveraging the mechanical resonance of BAW and SAW modes, ME sensors achieve the femto- to pico-Tesla sensitivity ideal for biomedical applications, while ME antennas, operating at acoustic resonance, allow significant size reduction, with high radiation gain and efficiency, which is suited for bandwidth-restricted applications. In addition, ME non-reciprocal magnetoacoustic devices using hybrid magnetoacoustic waves present novel solutions for RF isolation, which have also shown potential for the efficient control of quantum defects, such as negatively charged nitrogen-vacancy (NV−) centers. Continued advancements in materials and device structures are expected to further enhance ME device performance, positioning them as key components in future bio-sensing, wireless communication, and quantum information technologies. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation into the noise characteristics of various slanted wall configurations. The study focuses on the noise suppression effects of cavities with slanted walls on cavity coupling noise. A total of eight configurations, with different slanting angles on the front and rear walls, were analyzed by varying the inclination of the inner wall. Noise and flow field measurements were conducted in an aeroacoustic wind tunnel, utilizing microphones for near-field and far-field noise data acquisition and hot-wire probes for flow field analysis. The results indicate that larger slant angles lead to more effective noise reduction. As the slant angle increases, the acoustic resonance frequency associated with the slanted inner wall rises, which alters the self-excited oscillation modes involved in coupling with the acoustic resonance. This reduces the impact of coupling on the sound pressure levels. The change in acoustic resonance frequency also modifies the phase delay term of the dominant mode, ultimately leading to a shift in the noise frequency. [ABSTRACT FROM AUTHOR]

The advent of the new 5G communication standard has introduced demanding requirements for the performance of RF front-end filters, necessitating high frequency, large bandwidth, and other improved parameters. Consequently, researchers have been actively investigating the potential of surface acoustic wave resonators and film bulk acoustic resonators to address these needs, leading to the development of numerous novel structures. Through finite element simulation, a new heterogeneous stack structure Al/LN/diamond/Si with an interdigitated electrode resonant cavity is proposed. And the advantageous role of a diamond thin film in the surface acoustic wave resonant structure, including the excitation of high-frequency acoustic resonance modes and modulation of the electromechanical coupling coefficient has been studied. This structure holds promise for addressing the increasing demands for high-frequency, large-bandwidth RF front-end filters in the context of the new 5G communication standard. The results show that the central resonant frequency of the new structure resonator is 5284 MHz, the electromechanical coupling coefficient is 10.96%, and the Q factor value is 10 316, which has potential application value in the field of high-frequency filtering. [ABSTRACT FROM AUTHOR]

High vibration poses significant safety and operational risks to compressor components. This study presents a thorough investigation of the root causes analysis and corrective actions to resolve vibration-induced failures faced on the suction system of a reciprocating compressor. Excessive pressure pulsations in the suction bottle and strong mechanical coupling between the cylinders and suction bottle due to high cylinder gas forces were identified as the root causes of vibration-induced failure of the suction system. The proposed solutions to eliminate this problem were implemented by splitting the suction bottle into two parts and making one bottle as an acoustic filter (Helmholtz resonator). The acoustic filter was optimized for the suppression of pressure pulsations above its Helmholtz frequency and also for the avoidance of acoustic and mechanical resonance. After applying the proposed solutions, the modified suction system achieved a 14.3-61.1% reduction in vibration and a 75.56% reduction in peak-to-peak pressure pulsation for the compressor operating at 1000 rpm. The processing capacity of the compressor has been increased by 6.82%. An acoustic filter is an effective low-cost technical measure for reduction of pressure pulsation and fluid-induced vibration, which greatly increases the reliability of the entire compressor system. [ABSTRACT FROM AUTHOR]

Ring resonator (RR) devices are closed-loop waveguides where waves circulate only at the resonant frequencies. They have been used in sensor technology and optical tweezers, but controlling micron-scale particles with optical RR tweezers is challenging due to insufficient force, short working distances, and photodamage. To overcome these obstacles, an acoustofluidic RR-based tweezing method is developed to manipulate micro-sized particles that can enhance particle trapping through the resonance interaction of acoustic waves with high Q factor (>3000), more than 20 times greater than traditional acoustic transducers. Particles can be precisely manipulated within the RR by adjusting the signal phase, with trapping amplified by enlarging the connected waveguide. Rapid particle mixing is achieved when particles are placed between the waveguide and RR. The signal path is strengthened by strategically positioning the RR in a two-dimensional plane. Acoustofluidic RR tweezers have immense potential for advancing applications in biosensing, mechanobiology, lab-on-a-chip, and cell-cell communication research. [ABSTRACT FROM AUTHOR]

Aiming at the poor film evenness in conventional ultrasonic spraying coating methods, an acoustic resonance atomization (ARA) is proposed for spray coating on silicon wafers using an in-house experimental prototype. By modulating the acoustic pressure distribution in the optimized acoustic chamber, the ARA can achieve atomized photoresist droplets with $\sim 8.5~\mu $ m in median diameter and concentrated droplet concentration. For mesoscale photoresist droplets, the uniform film of AZ P4620 photoresist is coated on silicon wafers by exploring and optimizing the substrate temperatures and spray velocity. The mechanism of uniform film formation by mesoscale photoresist droplets is explored. Smaller droplets can effectively fill the micro-gaps within the photoresist film layer, forming a dense and uniform film. The experimental results demonstrate that the employed coating process can obtain a controllable photoresist film thickness and evenness index of less than 5% with a high-quality film layer, which provides an alternative technological solution for the spray coating. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study and performance analysis of all-oxide thin-film Au/Pt/Ba 0.5 Sr 0.5 TiO 3 /SrMoO 3 varactors with 100 nm Ba 0.5 Sr 0.5 TiO 3 (BST) tunable dielectric layers doped with 1%, 3% and 5% of Mn and Ni grown epitaxially on a 600 nm SrMoO 3 bottom electrode. Performance parameters such as tunability, quality factor, figure-of-merit, leakage current and acoustic resonances of the varactors are investigated. The investigation covers frequencies up to 6 GHz and a broad temperature range from − 40 ∘ to 80 ∘ , using biasing field strengths of up to ± 100 V/μm, in order to evaluate the feasibility and the performances of BST-doped all-oxide varactors for sub-6 GHz applications. Results confirm the anticipated advantages of Mn and Ni doping: a substantial reduction in leakage current along with an increase in quality factor, however, at the cost of reduced tunability. The observed acoustic resonances are shifted towards higher frequencies as compared to those for varactors with undoped BST, which implies in a larger frequency operating range for doped all-oxide varactors. In addition, the amplitudes of the acoustic resonances decline with doping. Moreover, they can be effectively suppressed for thinner BST layers, which has been proved exemplarily for a varactor with a 25 nm Mn-doped BST layer and a tunability of 55 %, requiring an ultimately low tuning voltage of only 2.9 V. [ABSTRACT FROM AUTHOR]

Purpose: Our study aims to assess the open-fitting capabilities and vent properties of traditional open-fitting behind-the-ear (open BTE) hearing aids to instant-fit open-fitting completely-in-the-canal (open CIC) systems. Methods: The study analysed data from 40 patients grouped in two groups based on the used hearing aids. Free field pure tone and speech audiometry were performed to obtain the free-field pure tone average and free-field word recognition score (WRS). The matrix sentence test was employed to evaluate the auditory performance and functional outcomes of patients. The Satisfaction with Amplification in Daily Life (SADL) and the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire were used to assess the personal satisfaction and benefit provided by the hearing aid. Real ear measurements were conducted to objectively evaluate the Real-Ear Unaided Gain (REUG) and Real-Ear Occluded Gain (REOG) of the two groups. For this purpose, six frequency bands (band 1 from 125 to 200 Hz, band 2 from 250 to 400 Hz, band 3 from 500 to 800 Hz, band 4 from 1000 to 1600 Hz, band 5 from 2000 to 3150 Hz, and band 6 from 4000 to 6300 Hz) were defined and compared. Results: Free-field WRS exhibited a significant difference (p-value = 0.004) between open BTE and open CIC, with better results for the open BTE. Matrix test speech reception threshold scores did not differ significantly between groups. No statistical significant difference were observed between APHAB and SADL total scores. Correlation tests revealed a negative correlation between SRT and APHAB scores in the open BTE group, not seen in the open CIC. No statistically significant difference was observed for all bands of REUG values, demonstrating comparability in terms of acoustic resonance of the external auditory canal. Comparing the REOG recorded in the two groups a significant difference was observed for bands 2 through 6. While the average REOG values for bands 5 and 6 were higher in patients with traditional open BTE aids, in contrast, for bands 2, 3, and 4, the REOG values for the open CIC group were higher and statistically significant compared to patients wearing traditional open-fitting BTE hearing aids. Conclusion: Patients with open CIC seem to perform worse in quiet environments compared to noisy ones, as indicated by the free field WRS score. However, the absence of differences in functional performance assessed with the matrix sentence test, and in the psychosocial aspects, makes these devices a good solution for individuals who reject hearing aids due to aesthetic concerns. The differences in terms of real ear measurements, while statistically significant, do not negatively impact overall performance. [ABSTRACT FROM AUTHOR]

The detection of debonding defects in thin-walled adhesive structures, such as clad-iron/rubber layers on the leading edges of helicopter blades, presents significant challenges. This paper proposes the application of electromagnetic acoustic resonance technology (EMAR) to identify these defects in thin-walled adhesive structures. Through theoretical and simulation studies, the frequency spectrum of ultrasonic vibrations in thin-walled adhesive structures with various defects was analyzed. These studies verified the feasibility of applying EMAR to identify debonding defects. The identification of debonding defects was further examined, revealing that cling-type debonding defects could be effectively detected using EMAR by exciting shear waves with the minimum defect diameter at 5 mm. Additionally, the method allows for the quantitative analysis of these defects in the test sample. Due to the limited size of the energy exchange region in the transducer, the quantitative error becomes significant when identifying debonding defects smaller than this region. The EMAR identified debonding defects in clad-iron structures of rotor blades with a maximum error of approximately 15%, confirming its effectiveness for inspecting thin-walled adhesive structures. [ABSTRACT FROM AUTHOR]

The oscillating quartz tuning fork method has been used to study resonance phenomena in experimental cells of different sizes filled with superfluid 4He and concentrated liquid mixtures of 3He–4He. An analysis of the temperature dependence of the resonance frequencies of the tuning forks showed that in a number of cases, the incompressible fluid model is not sufficient to interpret the experimental results and that acoustic processes in the cell should be taken into account. The frequencies of the resonances of the first sound in cylindrical geometry are estimated and their influence on the resonant frequencies of the tuning fork is shown, which can lead to a distortion of the shape of the resonant line. A comparison is made between experimental results for superfluid 4He and mixtures of 3He-4He with light isotope concentrations of 5% and 15%. It is shown that, in contrast to pure helium, the model of a viscous incompressible fluid cannot be applied to mixtures, even in the absence of first acoustic resonances. This can be explained by the fact that, when studying concentrated solutions, the excitation of the second sound along with the first can have a noticeable effect on the resonance characteristics of the tuning fork. [ABSTRACT FROM AUTHOR]

Impinging jets are encountered in many industrial applications. Previous studies have considered different parameters that affect the flow and enhance mass and energy transfer of these flows, such as Reynolds number, nozzle geometry, nozzle-to-plate distance, wall material and angle, and the flow regime at the jet exit. Furthermore, the dynamics of these jets could be a source of a high level of noise when the transfer of energy is optimized between the aerodynamic and acoustic fields. This can lead to a resonant jet producing self-sustained tones. Self-sustained tones are related to aero-acoustic coupling and occur in impinging jets when a feedback loop is present between the jet exit and the impinged plate. Few studies that deal with the heat transfer of an impinging jet in the presence of an acoustic resonance have been conducted. This state of the art review and discussion will focus on the heat transfer and flow dynamics in such noisy and resonant configurations. Such investigation will allow us to understand how a similar regime characterized by acoustic instabilities could be useful in enhancing heat transfer at the wall. [ABSTRACT FROM AUTHOR]

Ultrasound spectroscopy up to 6 MHz is carried out on a 12 Ah Lithium‐ion battery pouch‐cell. The analysis revealed that the attenuation behavior can be effectively described as having an absorption component and a resonance component. It was demonstrated that the absorption can be modeled as a second order polynomial. Two distinct resonances were identified at 2.2 MHz and 4.4 MHz. The first of these resonances shows a significant almost linear reduction in magnitude with increasing state of charge. By smartly choosing the ultrasound interrogation frequency to coincide with this resonance, an almost linear increase by a factor of more than five was measured in the signal amplitude between between state of charge levels of 0 and 100. This could provide the basis for a robust and straightforward state of charge determination method. [ABSTRACT FROM AUTHOR]

Surface acoustic wave devices are ubiquitously used for signal processing and filtering, as well as mechanical, chemical, and biological sensing and show promise as quantum transducers. While surface acoustic waves (SAWs) are primarily excited and driven using electromechanical coupling and interdigital transducers, there is a strong desire for novel methods that enable the coherent excitation and detection of SAWs all-optically interfacing with photonic integrated circuits. In this work, we numerically model and experimentally demonstrate SAW excitation in integrated photonic waveguides made from GeAsSe glass via backward stimulated Brillouin scattering (SBS). We measure a Brillouin gain coefficient of 203 W−1 m−1 for the surface acoustic resonance at 3.81 GHz, with a linewidth narrowed to 20 MHz. Experimental access to this new regime of SBS not only opens up opportunities for novel on-chip sensing applications by harnessing the waveguide surface but also paves the way for strong Brillouin interactions in materials lacking sufficient acoustic guidance in the waveguide core, as well as the excitation of SAWs in non-piezoelectric materials. [ABSTRACT FROM AUTHOR]

The article in the Journal of Fluid Mechanics explores the fluid-acoustic-structure resonance mechanism in a compressor blade cascade through wind tunnel testing. It delves into the interplay of fluid, acoustic, and structural factors in inducing blade vibration stress and fatigue cracks. The study reveals the significance of controlling flow dynamics to mitigate the risk of blade failure due to acoustic resonance. Overall, the research sheds light on the intricate interactions involved in compressor blade resonance phenomena. [Extracted from the article]

ABSTRACT This paper presents the results of a pilot landscape‐scale seismic survey undertaken in Apalachee Bay, Florida, across a submerged landscape that contains dozens of Pre‐Contact sites. In addition to the goals of improving the geophysical and remote sensing ground model for this submerged landscape, the survey also sought to undertake the first independent scientific test of the contentious ‘HALD’ methodology, an acoustic resonance method that it is claimed to identify knapped lithic artefacts at and/or below the seabed through the identification of distinct ‘haystack’ responses. The results of this work indicate that the HALD method, as currently described, produces results that could not be scientifically replicated in this survey. We conclude that any HALD ‘haystack’ signal should therefore not be considered as an example of detection of human‐modified lithic material but rather as a geophysical anomaly that requires additional constraints before it can be used to reliably identify human‐modified lithic materials. Thus, although the authors note that laboratory studies have successfully produced an acoustic signal in human‐modified lithics, the field‐based methods remain yet to be reliably determined. In addition to these results, the landscape mapping survey also recorded valuable information on buried and previously unrecorded landscape features that have archaeological significance and that may guide future site prospection. We therefore conclude that despite the results of the HALD test, the well‐preserved submerged landscape of Apalachee Bay region provides a highly useful testing ground for methods that can be deployed elsewhere globally. [ABSTRACT FROM AUTHOR]

Dynamic non-destructive methods (NDT) are particularly attractive owing to their time and cost efficiency when compared to conventional uniaxial compressive strength tests. However, the results of these methods are highly scattered; therefore, they are primarily used for qualitative material characterization. One of the most important NDT results is the calculation of the dynamic Young's modulus, which is associated to the uniaxial compressive strength (UCS) of concrete. The ultrasonic pulse velocity (UPV) is the most commonly used NDT. The limitation of this method is that it directly depends on knowledge of the Poisson's ratio, and an assumption of its value must be made. This assumption results in highly scattered results. In contrast, the impact echo method (IE) can result in a dynamic Young's modulus calculation without knowing the Poisson's ratio. The limitation of this method is that it is dependent on the specimen's slenderness, which in turn depends on the Poisson's ratio. This study investigates the IE method's applicability to short cylinders. A comparison of the UPV and IE methods is made, and the error in the dynamic Young's modulus value derived by assuming Poisson's ratio value in the UPV method is calculated. The authors conducted a numerical analysis and recently proposed the use of a shape correction factor (SCF) to apply the IE results for short cylinders, considering the influence of the slenderness (L/D) of the samples. For the first time worldwide, an extensive experimental study on 232 concrete samples with L/D - 1.0 confirmed the wide spread of UPV test results and showed that it can lead to an error on Young's Modulus determination by up to 50% owing to the adoption of an arbitrary Poisson's ratio value. In contrast, using the SCF yields IE results with a ±2% error. A new methodology, ultrasonic pulse impact echo synergy (UPIES), is proposed by performing both UPV and IE tests on the specimens and using the SCF. The Poisson's ratio and, consequently, the Young's modulus can be accurately determined. [ABSTRACT FROM AUTHOR]

The results of a consistent computational and experimental study of acoustic self-oscillations in an annular cavity surrounding a circular pipe with a local narrowing are given. In the experiment, pressure fluctuations were measured on the outer wall of the annular cavity for various volume flow rates; air entered the pipe at the atmospheric pressure. It was found that the flow regime with excitation of acoustic self-oscillations in the cavity is implemented in a certain range of flow rates. The oscillation frequency corresponds to the first natural frequency, and the root-mean-square values of pressure fluctuations reach a level of 2300 Pa. Numerical simulation based on the RANS approach, carried out for the geometry and conditions of experiment, reproduces the observed effect of acoustic excitation of the cavity and gives similar values of the fluctuation amplitude. The oscillation modes developed at various volumetric flow rates are analyzed based on the obtained calculated data. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reflection and transmission of acoustic waves by slabs composed of parallel cylinders randomly distributed in a fluid are investigated theoretically, numerically, and experimentally. Measurements of the reflection and transmission coefficients are carried out on samples of concentrations ϕ = 20 % and ϕ = 30 % of steel rods immersed in water. These results experimentally highlight the existence of Fabry–Pérot resonances in disordered slabs. Moreover, the experiments are in quantitative agreement with numerical simulations and a modeling based on multiple scattering theory. [ABSTRACT FROM AUTHOR]

Relying on scrap rates alone to assess process control in the foundry can be deceiving. Depending on the inspection method used, it is possible to sort grossly non-conforming parts, while still allowing a wide window of acceptance, masking a process that is out of control. Modern methods of acoustic resonance testing (ART) allow for detailed data logging of both part weight and resonant frequency peak data. Monitoring these two factors at the lot level can give foundry managers insight into how consistent their process is both within a single date code and across multiple date codes. The information collected during quality testing can and should be combined with statistical information gathered at the front of the foundry (design, tooling, molding, inoculation, pouring, cooling, and shakeout) and used to adjust the process to achieve smaller data spreads and more consistent and repeatable process control. Once a process is deemed to be under control, consideration should be given to monitoring the defined specification limits and subsequent control limits using statistical trend analysis as a means for ensuring a process is not approaching a condition in which the opportunity for quality issues can arise. [ABSTRACT FROM AUTHOR]

Vibration causes compressor rotor blade failure that affects aeroengine safety. Therefore, a plane cascade model of rotor blades was developed to capture the vibration phenomenon. The blade vibration, vortex shedding, and aerodynamic noise were measured. The results indicate that flow and noise induce a natural vibration mode, resulting in torsional vibration fatigue damage. The frequency of trailing edge vortex shedding is consistent with the frequency of tip clearance leakage vortex pulsation and is close to the second-order modal frequency of the blade, which induces torsional vibrations. The triple frequency of the background noise peak frequency in the wind tunnel is consistent with the first standing wave acoustic resonance modal frequency of the cascade experimental section duct and is close to the third-order natural modal frequency of the blade, which induces bending and torsional vibrations. This research provides guidance for the study of rotor blade multifield coupling-induced vibration. [ABSTRACT FROM AUTHOR]

An acoustic gas thermometry system, which introduces a one-liter quasi-spherical resonator (QSR) made of oxygen-free copper, built at the National Metrology Institute of Japan (NMIJ/AIST), has been employed to measure thermodynamic temperatures from the triple point of water down to the triple point of mercury. The measurement adopted a thermostatic bath operated down to 263.15 K and a new one that can operate down to lower temperatures. The present acoustic gas thermometry system measured the speed of sound in argon on the isothermal curves of the triple point of water, 268.15 K, 263.15 K, 253.15 K, 243.15 K and at the triple point of mercury under the pressure range from 500 kPa down to around 60 kPa. Based on the measured speed of sound, the thermodynamic temperatures at the mentioned isotherms were determined relatively from the speed of sound at the triple point of water. Using the measured thermodynamic temperature T, the difference between T and the temperature T90, based on the International Temperature Scale of 1990 (ITS-90), (T − T90), along with the associated uncertainties, u(T − T90), were determined to be − 0.4 ± 1.1 mK for 268.15 K, − 1.0 ± 0.9 mK for 263.15 K, − 1.9 ± 0.9 mK for 253.15 K, − 2.5 ± 0.9 mK for 243.15 K and − 2.7 ± 0.9 mK for 234.3156 K. The present (T − T90) values were found to be consistent in all cases within the estimated uncertainty with the currently reported values existing in overlapping temperature range. [ABSTRACT FROM AUTHOR]

Control effects of leading-edge grooves on deep cavity noise are investigated numerically. The length-to-depth ratio of the grooves are 0.5, 1, and 4, respectively. The freestream Mach number is equal to 0.16, corresponding to the Re based on the cavity length of 7.7 × 105. The Detached Eddy Simulations (DES) combined with Ffowcs Williams–Hawkings (FW-H) acoustic analogy are adopted to simulate the characteristic information of the flow field and the acoustic field. The analysis results show that all grooves investigated in this paper have a certain noise control effect, and the groove with the most obvious noise reduction effect is the groove with a length-to-depth ratio of 0.5, namely, the deep groove. Narrowband noise generated by the flow-acoustic feedback (100–700 Hz) and the acoustic resonance mechanism (above 300 Hz) and broadband noise caused by the turbulent disturbance in the shear layer of the cavity mouth significantly reduce when the deep groove is used for the noise control. The reason for the noise reduction is that the leading-edge grooves can effectively change the flow characteristics near the mouth of the downstream cavity. When the flow passes the grooves, the groove flow reduces the energy in the fluid, resulting in the significant decrease of flow velocity of the boundary layer of the incoming flow of the cavity. In addition, the use of the deep groove also promotes the vortex concentration position to move towards the bottom of the cavity, pushes the energy in the shear layer of the downstream cavity towards the front-edge as well as the bottom of the cavity, and stabilizes the development of the shear layer near the cavity mouth. [ABSTRACT FROM AUTHOR]

Tire acoustic cavity resonance (TACR) noise is one kind of low-frequency and narrowband noise that particularly annoys passengers, especially becomes more prominent in electric vehicles. This paper demonstrates a numerical investigation on the TACR noise via the acoustic-structural coupling finite element model. The accuracy of this coupling finite element model is validated both by the analytic method based on the superposition theory of traveling waves and experimental modal tests of tire cavities. According to the simulated models, the influences of external factors including the inflation pressure and road load on the TACR noise are studied. Meanwhile, as the main constituent component in the tire model, the effect of belt cord is also discussed. To design the low-TACR noise tire, various design parameters of the inner contour in tire cavity are analyzed. By the orthogonal test and range analysis, it is found that the contour parameters can slightly affect the modal frequency and sound pressure of TACR noise. Among these, the curvature radius of the tire shoulder ρ 4 , tire sidewall ρ 5 , and half-section height H have a more obvious influence on the TACR noise than the curvature radius of the tire crown region ρ 2 and transition region ρ 3 . Meanwhile, it also illustrates that increasing the curvature radius at the tire shoulder ρ 4 and reducing the half-section height H has a reduction effect on the TACR noise. This study can contribute to the design of low road noise tires. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Donghua University (English Edition) is the property of Journal of Donghua University Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface acoustic wave (SAW) sensors in tunable oscillator configuration, with a deposited polymeric layer, were used to investigate the layer's impact on the oscillator's resonant frequency. The SAW oscillators were tuned by means of variable loop amplification. Full-range amplification variation led to a resonant frequency increase of ~1.7 MHz due to the layer's nonlinear reaction. The layer's morphology and location resulted in a specific resonant frequency–amplitude dependence. Five types of layers were used to test the causal linkage between the layers' morphological parameters or positioning and the SAW oscillator's resonant frequency. The frequency variation trend is almost linear, with a complex minute variation. Small amplitude sigmoids occur at certain attenuation values, due to layer acoustic resonances. Multiple sigmoids were linked with layer resonances of different orders. A good correlation between the layer's thickness and resonance position was found. [ABSTRACT FROM AUTHOR]

It is demonstrated that the application of piezoelectric sensors to metallic bars and strands can enable determining the status of the integrity of these elements through the spectrum of their acoustic excitations. The voltage output of the piezo, secured to metal bars or strands, is fed to the input of a Fast Fourier Transform analyzer, which allows displaying the spectrum of the excitations from which information on the length, overall quality of the metal, and the presence of defects can be obtained. We show that the analysis, performed on several materials and strands of different lengths, could be useful for cases in which visible inspection and/or direct access to the entire body of the metallic elements is not possible. Applications of our study for testing metallic structures embedded in concrete foundations are reported for construction sites. [ABSTRACT FROM AUTHOR]

Background: Acoustic resonance therapy (ART) is a novel vibrational treatment that delivers patient-specific resonant frequency acoustic energy to the sinonasal cavities. In a pilot study, ART was effective for the acute treatment of nasal congestion. We conducted a sham-controlled randomized trial to validate the efficacy of ART when administered daily for 2 weeks. Methods: A total of 52 adult patients were enrolled in a multi-center, randomized, double-blinded, sham-controlled, interventional study evaluating ART administered by a vibrational headband. Patients received either active treatment or a non-therapeutic sham treatment twice daily over 2 weeks. Clinical endpoints were the average change in nasal congestion sub-score of the Total Nasal Symptom Score (TNSS) and the average change in composite TNSS. Results: ART resulted in a significantly greater mean change in the nasal congestion sub-score compared to sham (-0.87 [95% confidence interval [CI] -1.11, -0.62] vs. -0.44 [95% CI -0.64, -0.23], p = 0.008). ART also resulted in a significantly greater reduction in the composite TNSS versus sham, (-2.85 [95% CI -3.85,-1.85], vs.-1.32 [95% CI-2.27,-0.36], p=0.027). The response rate, determined by a nasal congestion sub-score minimal clinically important difference of 0.23, was 80.8% for ART and 46.2% for sham, with an adjusted risk ratio of 1.95 (95% CI 1.26, 3.02, p=0.003) in favor of ART. Safety endpoints showed no adverse events. Conclusion: ART is a safe and effective non-pharmacologic alternative for the treatment of nasal congestion. [ABSTRACT FROM AUTHOR]

In the field of new environmental energy harvesting technology, wind energy and piezoelectric energy harvesting have become research hotspots. By utilizing wind energy into vibration energy, i.e., wind-induced vibration effect is a research hotspot in the field of environmental energy harvesting. This article comprehensively analyzes the research status and development trend of piezoelectric energy harvesters based on wind-induced vibration effects at home and abroad. It was found that the conversion process of wind energy to vibration energy is mainly based on flutter, galloping, and acoustic resonance. The conversion of vibration energy into electrical energy is mainly piezoelectric power generation, supplemented by magnetic induction power generation and friction power generation. For high power density and small volume application scenarios, resonant cavity type wind vibration energy collection is the main development trend. [ABSTRACT FROM AUTHOR]

Cell‐laden hydrogel fibers/tubules are one of the fundamentals of tissue engineering. They have been proven as a promising method for constructing biomimetic tissues, such as muscle fibers, nerve conduits, tendon and vessels, etc. However, current hydrogel fiber/tubule production methods have limitations in ordered cell arrangements, thus impeding the biomimetic configurations. Acoustic cell patterning is a cell manipulation method that has good biocompatibility, wide tunability, and is contact‐free. However, there are few studies on acoustic cell patterning for fiber production, especially on the radial figure cell arrangements, which mimic many native tissue‐like cell arrangements. Here, an acoustic cell patterning system that can be used to produce hydrogel fibers/tubules with tunable cell patterns is shown. Cells can be pre‐patterned in the liquid hydrogel before being extruded as cross‐linked hydrogel fibers/tubules. The radial patterns can be tuned with different complexities based on the acoustic resonances. Cell viability assays after 72 h confirm good cell viability and proliferation. Considering the biocompatibility and reliability, the present method can be further used for a variety of biomimetic fabrications. [ABSTRACT FROM AUTHOR]

The study investigates the effect of the type of varnish and the number of layers on some acoustic properties of the resonance spruce in combination with the changes produced in some physical, morphological, and chemical properties of wood. In addition to color changes and surface chemistry, the surface roughness and morphology are modified by the thickness of the varnish film, 10 layers being optimal from this point of view, as well as the oil‐based finish. The sound absorption coefficient increases with the number of varnish layers and varies with the sound frequency range, varnish type, and wood quality, all contributing to the acoustic tunability. For example, for a sound frequency of 1.5 kHz, it is observed that the oil‐based varnish with 5 and 10 layers contributes to a full sound, while the alcohol varnish, due to a lower absorption coefficient for this frequency, can lead to some nasal sounds. Applying more than 10 layers of varnish does not improve the sound performance as it will soften the sound in an oil‐based finish and make the sound too sharp in the case of alcohol–varnished wood. [ABSTRACT FROM AUTHOR]

This research unveils the profound cultural, artistic, and technological dimensions of ancient musical instruments during the Spring-Autumn and Warring States Periods (approximately 771-221 BCE) in ancient China. Through a multidimensional exploration, it delves into four key variables: Musical Instrument Archaeology, Acoustic Properties and Resonance, Cultural Significance of Music, and Technological Advancements and Artistic Innovation. Historical accounts and archaeological findings converge to paint a vivid picture of the integral role of music in these ancient civilizations. The relics unearthed at various sites, including intricately crafted stringed instruments and resonant percussion artifacts, bear witness to the artistry and craftsmanship of the era. The study further probes the auditory dimensions of these instruments, deciphering the science of sound and exploring the physical attributes that endowed them with their distinct timbre and resonance. This acoustic analysis allows for a profound sonic connection with the past. Moreover, the research underscores the cultural significance of music, revealing how it functioned as a conduit for conveying cultural values, stories, and societal norms. It explores the emotional and communal resonance of music in rituals, ceremonies, and everyday life. Finally, the study reveals the interaction between technological improvements and artistic invention, demonstrating craftsmen' resilience and originality during this transitional era. In essence, this research bridges the gap between the past and the present, providing a thorough knowledge of music's complex function in ancient China and echoing the continuing human interest with music as a cultural light that transcends time and place. [ABSTRACT FROM AUTHOR]

Characteristic timescales for rotating detonation rocket engines (RDREs) are described in this study. Traveling detonations within RDREs create a complex reacting flow field involving processes spanning a range of timescales. Specifically, characteristic times associated with combustion kinetics (detonation and deflagration), injection (e.g., flow recovery), flow (e.g., mixture residence time), and acoustic modes are quantified using first-principle analyses to characterize the RDRE-relevant physics. Three fuels are investigated including methane, hydrogen, and rocket-grade kerosene RP-2 for equivalence ratios from 0.25 to 3 and chamber pressures from 0.51 to 10.13 MPa, as well as for a case study with a standard RDRE geometry. Detonation chemical timescales range from 0.05 to 1000 ns for the induction and reaction times; detonation-based chemical equilibrium, however, spans a larger range from approximately 0.5 to 200 μ s for the flow condition and fuel. This timescale sensitivity has implications regarding maximizing detonative heat release, especially with pre-detonation deflagration in real systems. Representative synthetic detonation wave profiles are input into a simplified injector model that describes the periodic choking/unchoking process and shows that injection timescales typically range from 5 to 50 μ s depending on injector stiffness; for detonations and low-stiffness injectors, target reactant flow rates may not recover prior to the next wave arrival, preventing uniform mixing. This partially explains the detonation velocity deficit observed in RDREs, as with the standard RDRE analyzed in this study. Finally, timescales tied to chamber geometry including residence time are on the order of 100–10,000 μ s and acoustic resonance times are 10– 1000 μ s. Overall, this work establishes characteristic time and length scales for the relevant physics, a valuable step in developing tools to optimize future RDRE designs. [ABSTRACT FROM AUTHOR]

This paper attempts to ascertain the thermal and acoustic impacts of introducing a vegetative roof layer on insulated and uninsulated metal roofs for tropical climates, through field measurements in Skudai, Johor, Malaysia, that were conducted for both dry and wet days. Four small-scale roof modules were tested, namely an uninsulated metal roof (uiMDR), an insulated metal roof (iMDR), and two identical corresponding modules with an additional vegetative component (uiGR and iGR, respectively). Outdoor ambient temperature (Tamb) was the most influential correlated variable affecting the roof outer surface temperature (RTOS) in 50% of the assessed scenarios. On the selected dry day, the inter-quartile ranges (IQR) of iGR, iMDR, uiGR, and uiMDR were 6.21 °C, 8.32 °C, 6.69 °C, and 1.66 °C, respectively; the IQRs were 1.6 °C, 4.11 °C, 2.59 °C, and 1.78 °C, respectively, on the selected wet day. Based on design U-value calculations, iGR was better than iMDR and uiMDR for both dry and wet days. The U-value of uiGR was also better than iMDR under dry-day conditions. The Wilcoxon signed-rank test also indicated a statistically significant difference in the roof inner surface temperature (RTIS) measurements (p-value = 0.00) during Malaysian daylight hours, between 8.00 a.m. and 6.00 p.m., regardless of the weather. In terms of sound level reduction under dry-day conditions, the Kruskal–Wallis and Wilcoxon signed-rank tests showed statistically significant differences in sound level reductions, with iGR and uiGR performing better than iMDR and uiMDR (p-values = 0.00). The sound level reductions for iGR, iMDR, and uiGR were 51%, 32%, and 31%, respectively, while uiMDR experienced sound level amplifications by 6%, possibly due to the acoustic resonance effect. This proof of concept may encourage a broader application of extensive GRs in Malaysia using metal roofs, beyond the conventional RC base construction method. [ABSTRACT FROM AUTHOR]

The aeroacoustic feedback loops in high-speed circular jets that impinge on a large flat plate are investigated via acoustic measurements and schlieren visualizations. In the present experiments, the nozzle pressure ratio ranges from 1.39 to 2.20, the corresponding ideally expanded jet Mach number Mj is from 0.70 to 1.12 and the nozzle-to-plate distance (H) is from 4.0D to 6.0D, where D is the nozzle exit diameter. The results of acoustic measurements show that the strongest tones are generated in a limited frequency band. The empirical dispersion relations obtained from the fluctuating greyscales along the jet centreline of time-resolved schlieren images have good agreement with the dispersion relations from the vortex-sheet model. The coherent flow structures at tonal frequencies are extracted by spectral proper orthogonal decomposition and are analysed in detail. For the Mj < 0.82 jets, the upstream-propagating guided jet mode is progressively confined to the potential core of jets with increasing tonal frequency, which provides the first direct experimental support for theoretical results. The evolution in the structures of acoustic resonance loops is studied along a single frequency stage of axisymmetric impinging tones. When the acoustic resonance between the upstream- and downstream-propagating guided jet modes is formed at tonal frequencies, the impinging tones are intenser. Slightly underexpanded impinging jets can simultaneously produce impingement tones and screech tones. Shock-cell structures have modulatory effects on the downstream-propagating Kelvin-Helmholtz wavepacket and the upstream- and downstream-propagating guided jet modes. Due to the interaction between the flow structures at the frequencies of impinging and screech tones, tones of axisymmetric modes can be produced outside the frequency ranges in which the axisymmetric upstream-propagating guided jet modes are supported by jets. [ABSTRACT FROM AUTHOR]

A study concerning the influence of flow on the Herschel–Quincke duct is presented here, which includes the numerical model, the acoustic source and the absorption condition called the Perfectly Matched Layer. For the excitation of a sound field, a normal mode wave is placed at the inlet of the tube. The function of PML is to simulate the infinite tube and avoid the reflection of acoustic wave. To investigate the influence of flow field on sound field, a coupled calculation method combining the finite element method and computational fluid dynamics is used to solve the linearized Euler equation, named the Galbrun equation. Firstly, the influence of the cross-section of the tube on the acoustic field is considered. Secondly, the effects of flow on the acoustic field is also investigated. Lastly, a comparative analysis of the simulation results reveals the influence of flow and other parameters of the tube on sound propagation. Both the Mach number and the cross-section ratio have an influence on the acoustic resonance, and the resonance frequency decreases with the increase in the cross-section ratio. [ABSTRACT FROM AUTHOR]

The article focuses on the origins and evolution of hip hop, highlighting DJ Kool Herc's pivotal role in its emergence at 1520 Sedgwick Avenue in the Bronx, New York in 1973. Topics discussed include the debate over hip hop's starting point, the influence of artists like The Sugarhill Gang and The Last Poets, and the cultural significance of hip hop as a form of intellectual and ideological production.

This article examines the role of sound and acoustics in academic conferences, with a specific focus on the Society for Ethnomusicology's annual meeting in 2023. The author discusses how the treatment of sound at the conference contributes to the production of knowledge in the field of ethnomusicology and raises important ethical and political considerations. The article highlights instances where sound disruptions affect the integrity of presentations and raises questions about the strategies for sharing research in conference spaces. The use of movable partition walls in conference venues is also explored, with a discussion on how they can create separate spaces for different sounds and presentations. However, the author critiques the partitioning logic, arguing that it reinforces a self-interest mindset and limits interdisciplinary and inclusive discussions. The article suggests the need for a more open and inclusive approach in the field of ethnomusicology. [Extracted from the article]

An investigation of the evolution process and propulsion performance of the longitudinal pulsed detonation (LPD) is conducted by numerical method in this study. Four computational models, model A–D, of different sizes are applied. A typical "deflagration surface–fast deflagration–LPD–forward shockwave" process of evolution is found for the duration of the LPD, and the LPD is intuitively triggered by the reflected shockwaves. Low injection pressure ratios (PRs; i.e., PR = 1.1–1.3) and combustors with a low length-to-height ratio (L/H) are found to be conducive to the sustenance of the LPD. In addition, based on the knowledge of the inherent acoustic resonance frequency, the sustainable LPD frequency is estimated. When the PR increases, the LPD frequency tends to decrease in the same model. In the evolution process of fast deflagration-LPD, the wave speed increases gradually, which is in good agreement with the previous study. In the propagation process of the forward shockwave, the wave speed increases in general, which is because the pressure difference between the combustor and the outlet accelerates the wave propagation. The propulsion performance of the LPD is also investigated. As the PR increases, the specific impulse I s p of all the four models increases in general. The I s p of the LPD is relatively low compared with that of the rotating detonation mode, and when realizing industrialization of the LPD-based engines, an LPD mode with higher work efficiency needs to be explored. We hope this study of the enlightening LPD mode can provide a foundation for the ensuing application of detonation-based engines. [ABSTRACT FROM AUTHOR]