Transmission Of Acoustic Waves Research Articles

Research on acoustic conduction mechanism of underwater acoustic channel based on metamaterials

In underwater acoustic communication, there are problems of low transmission efficiency, severe loss, and inaccurate point-to-point transmission. To realize the efficient transmission of underwater acoustic communication based on finite element analysis, a metamaterial-based underwater acoustic channel model was designed using COMSOL Multiphysics 5.3 software, and its acoustic conduction mechanism was studied. It was found that the directional transmission of sound waves with low loss was achieved when the sound waves generated by the point sound source pass through the underwater acoustic channel. In addition, the periodic structure of local resonance was proposed to generate the multi-directional acoustic waves, which can control the acoustic wave transmission direction arbitrarily and improve the transmission efficiency of underwater acoustic communication. This indicates a new direction for long-distance and efficient transmission of underwater acoustic communication.

Analysis of wave propagation through functionally graded porous cylindrical structures considering the transfer matrix method

This paper presents a study on acoustic wave transmission through functionally graded porous (FGP) cylindrical shells. The mechanical properties of the FGP material, such as porosity, vary continuously along the thickness of the cylinder, considering a power-law distribution profile. According to a laminate model, the structure is assumed to be composed of a finite number of isotropic homogeneous porous sublayers. The extended full method (EFM) is used to describe the displacement and stress variables of each porous sublayer. Next, using the transfer matrix method (TMM), a local transfer matrix is established for each sublayer, which connects the field variables of the inner and outer surfaces of the sublayer. Eventually, the product of these transfer matrices for adjacent sublayers forms the global transfer matrix of the structure. The effects of different structural and environmental properties on sound transmission loss (TL) of the system are studied. The results show that TL is enhanced by increasing porosity of the outer surface of the cylinder, although enhancing the inner porosity adversely affects TL. Finally, it has been proved that by functionally grading a porous cylinder, sound insulation of the structure is improved dramatically in both mass and stiffness-controlled regions.

Phenomenological law for the acoustic reflection by an array of cylindrical cavities in a soft elastic medium

We propose a phenomenological model, built from results obtained by finite-element numerical simulations, for the transmission and reflection of acoustic waves by a two-dimensional array of cylindrical cavities in a soft elastic medium. We show that the acoustic properties of a cylindrical cavity can be described by two geometrical parameters: its aspect ratio (AR) and the radius of the sphere of equivalent volume. Cylinders with AR close to one are acoustically similar to spheres, whereas flat cylinders exhibit a lower resonance frequency and an increased damping due to their ability to emit shear waves. We provide an example of how our new phenomenological analytical model can help to design thin coatings that can turn strong acoustic reflectors into good absorbers.

Boundary-layer effects on electromagnetic and acoustic extraordinary transmission through narrow slits.

We study the problem of resonant extraordinary transmission of electromagnetic and acoustic waves through subwavelength slits in an infinite plate, whose thickness is close to a half-multiple of the wavelength. We build on the matched-asymptotics analysis of Holley & Schnitzer (2019 Wave Motion 91, 102381 (doi:10.1016/j.wavemoti.2019.102381)), who considered a single-slit system assuming an idealized formulation where dissipation is neglected and the electromagnetic and acoustic problems are analogous. We here extend that theory to include thin dissipative boundary layers associated with finite conductivity of the plate in the electromagnetic problem and viscous and thermal effects in the acoustic problem, considering both single-slit and slit-array configurations. By considering a distinguished boundary-layer scaling where dissipative and diffractive effects are comparable, we develop accurate analytical approximations that are generally valid near resonance; the electromagnetic-acoustic analogy is preserved up to a single parameter that is provided explicitly for both scenarios. The theory is shown to be in excellent agreement with GHz-microwave and kHz-acoustic experiments in the literature.

Features of Acoustic Wave Transmission through a Medium, Containing a Layer of Multifractional Bubbly Liquid

The mathematical model that determines reflection and transmission of an acoustic wave at different angles of incidence through a medium containing multifractional bubbly liquid is presented. The reflection and transmission coefficients of the wave are calculated for a water–bubble liquid–water mixture. The effect of the volume content of the dispersed phase on the studied coefficients is shown.

An improved method for mean flow boundary conditions for computational aeroacoustics

An accelerated method of specifying Mean Flow Boundary Conditions for an unsteady flow is developed. Computation domains are inevitably finite in size, which means that its boundaries have to be located within the flow itself. This requires special boundary conditions which do not reflect outgoing waves while still being able to impose any incoming disturbances into the computation domain. As is well known, the Euler equations contain acoustic, vortical, and entropy waves, and all possible flows can be made by combining them. Because these waves are coupled, it is difficult to separate them into individual waves that the solver can modify. Moreover, it is desirable to set not just the waves but the mean of the combination of these waves at the boundaries and this takes a very long time. In this work, a new method for imposing the desired time-averaged mean flow at these computational boundaries is introduced. To reduce the complexity of the problem, but retaining the basic physics and difficulties, one-dimensional acoustic wave transmission is used to model wave propagation through a nearly choked nozzle. Mean and unsteady flow equations solved, simultaneously; and integrated with the existing non reflecting boundary conditions, and is able to quickly and accurately achieve the desired mean flow without spurious reflections of the outgoing disturbances, not only for deterministic, but chaotic flows.

Laser ultrasonic monitoring of reversible/irreversible modification of a real crack under photothermal loading

We study the responses of laser-generated acoustic waves to localized reversible/irreversible modifications of microscopic asperities on crack surfaces during crack closure, which is an essential process in nonlinear photoacoustic/photothermal crack detection techniques. Our laser ultrasonics technique involves optical measurement of the transmission and mode conversion of the laser-generated surface acoustic waves caused by the crack. Reversible/irreversible modifications of asperities can be achieved via non-contact photothermal loading of the crack. Three photothermal loading cycles were realized in individual succession and were monitored using the laser ultrasonics technique at various experimental locations along the crack. In our experiments, each photothermal loading cycle includes multiple successive subcycles, in which the material is first heated and then cooled to its equilibrium temperature, thereby initiating local closing, followed by opening of the crack. Each subcycle is monitored twice using the laser ultrasonics technique, once each at the end of heating and cooling. Furthermore, each successive subcycle is accomplished at a higher power of heating laser than that of the previous subcycle. Significant differences in the peak-to-peak amplitude of the surface skimming longitudinal acoustic wave, which is excited by mode conversion of the Rayleigh wave by the crack, are revealed during the first cycle of photothermal loading. These differences clearly indicate a partial irreversibility of the mechanical processes occurring in the crack surfaces during subcycles of the first cycle. In a larger temporal scale, irreversible modification of crack surfaces is observed from the significant difference between the experimental results of the first photothermal loading cycle and the subsequent two cycles, whereas a reversible response of the crack surface to thermoelastic loading is observed from the similarity of the measurements accumulated during the two subsequent cycles.

Surface acoustic waves as a sensitive probe for photoresponsive polarization memory in SrTiO3

Transient electric polarization in single crystalline SrTiO3 (STO) substrates was studied by measuring the transmission of surface acoustic waves (SAWs). We applied a large dc electric field (8 × 106 Vm−1) to interdigital transducers (IDTs) on STO substrates in order to induce local piezoelectricity, which is required to generate and transmit SAWs. The resulting electric polarization and the retention thereof were analyzed as a function of time after the applied electric field was removed, by measuring transient SAW signals. The retained polarization turned out to provide strong electromechanical coupling, comparable to that resulting from the dc-field-induced piezoelectricity. SAW signals were observed for more than 30 h (in absence of an external dc electric field), which is evidence for a long-lasting retention of electric polarization. Remarkably, this polarization was found to be rapidly suppressed as the sample was exposed to visible light. By measuring the transient SAW transmission under illumination with light at different wavelengths, we identified photoconductivity and/or acceleration of oxygen vacancy migration by photon-induced splitting of bound vacancy pairs as the main mechanisms behind this photoresponsive memory effect.

Non-reciprocal transmission of microwave acoustic waves in nonlinear parity–time symmetric resonators

Acoustic waves have emerged as versatile on-chip information carriers with applications ranging from microwave filters to transducers. Nonreciprocal devices are desirable for the control and routing of high-frequency phonons. This is challenging, however, due to the linear response of most acoustic systems. Here, we leverage the strong piezoelectricity of lithium niobate to demonstrate fully tunable gain, loss, and nonlinearity for surface acoustic waves using electric circuitry. This allows the construction of a nonlinear acoustic parity-time-symmetric system and enables nonreciprocal transmission. We achieve a nonreciprocity of 10 decibels for a 200-MHz acoustic wave at a low input power of 3 $\mu$W and further demonstrate one-way circulation of acoustic waves by cascading nonreciprocal devices. Our work illustrates the potential of this piezoelectric platform for on-chip phononic processing and exploration of non-Hermitian physics.

Double topological edge states investigation in sonic metamaterials

We investigate the topologically protected sound propagation in sonic metamaterials, analogous to quantum spin hall effect (QSHE). The sonic metamaterials consist of circular rods and meta-molecules arranged in air with a honeycomb-lattice. The on-demand inversion in topological phase can be achieved by two ways of scatterer controls at locally resonant frequency and Bragg frequency. The Helmholtz resonators in the structure are contributed to the formation of subwavelength double Dirac cones which are more likely to appear due to local resonance enhancement with more number of resonators. By combining two sonic metamaterials with different topological invariants, we demonstrate the robust sound propagation and pseudospin-dependent one-way acoustic propagation at the interface. Experimental measurement of the topologically protected acoustic wave transmission matches well with the simulation result.

Power transmission characteristics of EWC-SPUDT SAW filters fabricated for multiplex transmission system of inverter gate drive circuits

To increase the electrical power transmission of surface acoustic wave (SAW) filters for gate drive systems of power conversion circuits, we fabricated unidirectional SAW filters based on a SiO2/Al/Pt/LiNbO3 structure in the frequency range of 380–950 MHz and measured their power durability characteristics. A transversal-type electrode-width-controlled single-phase unidirectional transducer (EWC-SPUDT) design was used to reduce the insertion loss of the SAW filters. Our experimental results showed that the transmitted electric power of the output port exceeded 560 mW, which was sufficient for the gate drive circuits. The results obtained demonstrate the validity of the SiO2/Al/Pt/LiNbO3 structure for the proposed EWC-SPUDT design.

Investigation on the influence coupling drilling fluid and formation boundary on acoustic wave propagation in drill string

Acoustic transmission along the drill string for measurement while drilling (MWD) is an effective solution to the problem of the low transmission rate that results from mud pulse transmission. However, the actual downhole acoustic waves are affected by many factors, such as drilling fluid properties and, formation boundaries, and their effects on acoustic wave transmission in drill string are not thoroughly understood. To solve this problem, a longitudinal vibration model was proposed for acoustic wave propagation in drill string, and the coupling effect of the viscous damping of drilling fluid and the contact between the drill bit and formation was taken into account. The finite difference method with second-order accuracy is used to solve the mathematical model. The results show that an increase in drilling fluid damping causes the amplitude of the acoustic wave to decrease linearly, but the effect is not significant. The formation boundary mainly affects the low-frequency response of the drill string channel, while having little impact on the high-frequency response. Based on the above analysis, this paper proposes adding an acoustic isolator in the bottom-hole-assembly that can be used to mitigate or eliminate the influence of the formation boundary on the acoustic signal in drill string. The numerical results indicate that such an acoustic isolator can effectively attenuate the noise and improve the amplitude-frequency characteristics of a low-frequency signal induced by acoustic transmission along the drill string.

Large Nonreciprocal Propagation of Surface Acoustic Waves in Epitaxial Ferromagnetic/Semiconductor Hybrid Structures

Non-reciprocal propagation of sound, that is, the different transmission of acoustic waves traveling along opposite directions, is a challenging requirement for the realization of devices like acoustic isolators and circulators. Here, we demonstrate the efficient non-reciprocal transmission of surface acoustic waves (SAWs) propagating along opposite directions of a GaAs substrate coated with an epitaxial Fe$_3$Si film. The non-reciprocity arises from the acoustic attenuation induced by the magneto-elastic (ME) interaction between the SAW strain field and spin waves in the ferromagnetic film, which depends on the SAW propagation direction and can be controlled via the amplitude and orientation of an external magnetic field. The acoustic transmission non-reciprocity, defined as the difference between the transmitted acoustic power for forward and backward propagation under ME resonance, reaches values of up to 20%, which are, to our knowledge, the largest non-reciprocity reported for SAWs traveling along a semiconducting piezoelectric substrate covered by a ferromagnetic film. The experimental results are well accounted for by a model for ME interaction, which also shows that non-reciprocity can be further enhanced by optimization of the sample design. These results make Fe$_3$Si/GaAs a promising platform for the realization of efficient non-reciprocal SAW devices.

Applying a functionally graded viscoelastic model on acoustic wave transmission through the polymeric foam cylindrical shell

This study presents an analytical solution for calculating sound transmission loss through a circular cylindrical shell made of polymeric foam. The intended cylinder is excited by an acoustic plane wave. The equations of motion for the cylindrical shell are derived by the first-order shear deformation. Besides, the polymeric foam is characterized using functionally graded Zener model in which the mechanical properties are varying continuously in the thickness direction as well as considering the frequency-dependent parameters. Due to the lack of study on the vibro-acoustic behavior of the viscoelastic graded materials, the results are compared with those of some researchers in the literature of elastic materials, and excellent concurrences are observed. Next, the effects of geometrical and material characteristics on the transmission loss factor are investigated. The influence of various power-law index illustrates that by reducing this parameter, the sound transmission loss through the shell is extensively increased. Finally, a comparison is performed along with four models of the cylindrical shells with the same weights including functionally graded viscoelastic, functionally graded, viscoelastic and elastic materials. As a key result, it can be explored that the sound transmission loss in a functionally graded viscoelastic shell is more enhanced than the other cylinders.

Transmission Characteristics of Ultrasonic Longitudinal Wave Signals in Negative Refractive Index Materials

Longitudinal waves have important applications in modern scientific research and production; as a special acoustic wave, longitudinal waves have a sound transmission performance in negative refractive index materials. This paper has designed a new structure for negative refractive index materials by virtue of COMSOL software and conducted related simulation analysis. Experimental results illustrated that the structure designed had good acoustic longitudinal wave transmission performance. Besides, the effect of sound wave focusing could be achieved by a combination of existing test methods. The design proposed could break the limitation of previous structures on acoustic longitudinal wave transmission. This study is expected to have important implications for the development of solid metamaterial structures.

Crack initiation of granite under uniaxial compression tests: A comparison study

Abstract In this study, a combination of acoustic emission (AE) method (AEM) and wave transmission method (WTM) is used to investigate the behaviors of AE and ultrasonic properties corresponding to initial fracturing in granitic rocks. The relationships of AE characteristics, frequency spectra, and spatial locations with crack initiation (CI) are studied. The anisotropic ultrasonic characteristics, velocity distributions in different ray paths, wave amplitudes, and spectral characters of transmitted waves are investigated. To identify CI stress, damage initiations characterized by strain-based method (SBM), AEM and WTM are compared. For granite samples, it shows that the ratio of CI stress to peak strength estimated by SBM ranges from 0.4 to 0.55, and 0.49–0.6 by WTM, which are higher than that of AEM (0.38–0.46). The CI stress identified by AEM indicates the onset of microcracking, and the combination of AEM and WTM provides an insight into the detection of rock damage initiation and anisotropy.

Symmetric and asymmetric spectra of acoustic waves resonantly transmitted through a slab in a fluid

We theoretically studied the resonant transmission of acoustic waves through a slab in a fluid. When acoustic waves are incident on the interface perpendicularly, Bright–Wigner type resonances occur, whereas Fano resonances are observed when acoustic waves are obliquely incident. We examine various resonance peaks in transmission using analytical expressions for the transmittance. In particular, we show that an antiresonance occurs when two types of resonance overlap at the same frequency.

Giant extraordinary transmission of acoustic waves through a nanowire.

Wave concentration beyond the diffraction limit by transmission through subwavelength structures has proved to be a milestone in high-resolution imaging. Here, we show that a sound wave incident inside a solid over a diameter of 110 nm can be squeezed through a resonant meta-atom consisting of a nanowire with a diameter of 5 nm equal to λ/23, where λ is the incident acoustic wavelength, corresponding to a transmission efficiency of 500 or an energy densification of ~14,000. This remarkable level of extraordinary acoustic transmission is achieved in the absence of ultrasonic attenuation by connecting a tungsten nanowire between two tungsten blocks, the block on the input side being furnished with concentric grooves. We also demonstrate that these "solid organ pipes" exhibit Rayleigh end corrections to their effective longitudinal resonant lengths notably larger than their in-air analogs. Grooves on the output side lead to in-solid directed acoustic beams, important for nanosensing.

Photoresponse in Multilayer Graphene during the Passage of a Surface Acoustic Wave

In this Letter, we studied the photoresponse in multilayer graphene on a lithium niobate (LiNbO3) crystal under the conditions of an electric potential applied to graphene and transmission of a surface acoustic wave. The acoustoelectric current in graphene when irradiated with light is shown to either increase or decrease depending on the polarity of the potential applied to graphene. A surface acoustic wave causes the appearance of a periodic charge lattice in graphene that enhances the interaction with incident light, which leads to an increase in the photoresponse.

Acoustic waves in granular packings at low confinement pressure

Elastic properties of a granular packing show a nonlinear behavior determined by its discrete structure and nonlinear inter-grain force laws. Acoustic waves show a transition from constant, pressure-dependent sound speed to a shock-wave-like behavior with an amplitude-determined propagation speed. This becomes increasingly visible at low static confinement pressure as the transient regime shifts to lower wave amplitudes for lower static pressure. In microgravity, confinement pressure can be orders of magnitude lower than in a ground-based experiment. In addition, the absence of hydrostatic gradients allows for much more homogeneous and isotropic pressure distribution. We present a novel apparatus for acoustic wave transmission measurements at such low packing pressures. A pressure control loop is implemented by using a microcontroller that monitors static force sensor readings and adjusts the position of a movable wall with a linear-motor until the desired pressure is reached. Measurements of acoustic waves are possible using accelerometers embedded in the granular packing as well as piezos. For excitation, we use a voice-coil-driven wall, with a large variety of signal shapes, frequencies, and amplitudes. This enables experiments in both the linear and strongly nonlinear regimes.