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Journal articles on the topic 'Multimodal acoustic propagation'

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1

Mangin, B., G. Gabard, and M. Daroukh. "In-duct flow computation and acoustic propagation using the admittance multimodal formulation." Journal of the Acoustical Society of America 155, no. 5 (2024): 3461–74. http://dx.doi.org/10.1121/10.0026091.

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A multimodal method for computing the potential base flow and propagating acoustic perturbations inside axisymmetric ducts is presented. Instead of using the standard modal basis, a polynomial basis is used in the radial direction to reduce the computational cost of the method, but this introduces non-physical high-order modes. The impact of these modes on the stability of the calculation is examined, and for the acoustic computation, a modification of the axial integration is proposed to improve the conditioning of the matrices involved. The flow computation is achieved by applying the method (initially devoted to acoustics) at a zero frequency without convective effects, by modifying the definition of the admittance at the exit of the duct, and by performing an induction process on the density. The method is validated against a finite element method for ducts with hard walls or lined walls. The results show that the proposed multimodal method is very efficient in computing the mean flow and propagating the sound disturbances inside axisymmetric ducts.
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2

Félix, S., and V. Pagneux. "Multimodal analysis of acoustic propagation in three-dimensional bends." Wave Motion 36, no. 2 (2002): 157–68. http://dx.doi.org/10.1016/s0165-2125(02)00009-4.

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3

Troian, R., D. Dragna, C. Bailly, and M. A. Galland. "Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow." Proceedings of the Mavlyutov Institute of Mechanics 11, no. 2 (2016): 150–55. http://dx.doi.org/10.21662/uim2016.2.022.

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Modeling of acoustic propagation in a duct with absorbing treatment is considered. The surface impedance of the treatment is sought in the form of a rational fraction. The numerical model is based on a resolution of the linearized Euler equations by finite difference time domain for the calculation of the acoustic propagation under a grazing flow. Sensitivity analysis of the considered numerical model is performed. The uncertainty of the physical parameters is taken into account to determine the most influential input parameters. The robustness of the solution vis-a-vis changes of the flow characteristics and the propagation medium is studied.
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4

Mangin, Bruno, and Gwénaël Gabard. "Acoustic radiation from an engine intake using an admittance multimodal method." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 5 (2023): 3513–24. http://dx.doi.org/10.3397/in_2023_0502.

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This paper presents an adaptation of the admittance multimodal method for computing the mean flow around an engine intake and the associated radiated acoustic field. The basic idea is to surround the engine with a fictive duct with a perfectly matched layer on its outer wall which simulates far-field conditions and avoids any acoustic reflection. The use of matching conditions between this duct and the engine duct allows for calculating the flow and acoustic admittance matrices (and then the associated fields) everywhere. The developed method, initially devoted to acoustic propagation, can also compute the mean flow field with some adjustments and is very efficient if some assumptions are added (typically an incompressible flow hypothesis in the far-field). The flow and acoustic results are then compared against a finite element method and highlight the accuracy and efficiency of the proposed approach.
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5

Liu, Juan, and Qi Li. "Coupled Mode Sound Propagation in Inhomogeneous Stratified Waveguides." Applied Sciences 11, no. 9 (2021): 3957. http://dx.doi.org/10.3390/app11093957.

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An efficient coupled mode method for modeling sound propagation in horizontally stratified inhomogeneous waveguides, in which the seabed is modeled as a (layered) acoustic medium, is presented. The method is based on Fawcett’s coupled mode method and the multimodal admittance method. The acoustic field is expanded onto the unusual local eigenfunctions composed by normal modes in the corresponding one-layer homogeneous waveguides with constant depth equal to the local total depth of the multilayered waveguide. A set of energy-conserving first-order differential equations governing the modal amplitudes of acoustic fields is derived. The admittance method is employed to solve the differential equations in a numerically stable manna. The coupled mode method considers the backscattering effect of inhomogeneities and full coupling between local modes, and offers improvement from the viewpoint of efficiency and computational cost. The acoustic fields predicted by the method agree well with those computed by the commercial finite element software COMSOL Multiphysics. The method can be extended to further establish fast and accurate 3D sound propagation models in complex shallow water environments.
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McTavish, James P., and Edward J. Brambley. "Nonlinear sound propagation in two-dimensional curved ducts: a multimodal approach." Journal of Fluid Mechanics 875 (July 19, 2019): 411–47. http://dx.doi.org/10.1017/jfm.2019.497.

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A method for studying weakly nonlinear acoustic propagation in two-dimensional ducts of general shape – including curvature and variable width – is presented. The method is based on a local modal decomposition of the pressure and velocity in the duct. A pair of nonlinear ordinary differential equations for the modal amplitudes of the pressure and velocity modes is derived. To overcome the inherent instability of these equations, a nonlinear admittance relation between the pressure and velocity modes is presented, introducing a novel ‘nonlinear admittance’ term. Appropriate equations for the admittance are derived which are to be solved through the duct, with a radiation condition applied at the duct exit. The pressure and velocity are subsequently found by integrating an equation involving the admittance through the duct. The method is compared, both analytically and numerically, against published results and the importance of nonlinearity is demonstrated in ducts of complex geometry. Comparisons between ducts of differing geometry are also performed to illustrate the effect of geometry on nonlinear sound propagation. A new ‘nonlinear reflectance’ term is introduced, providing a more complete description of acoustic reflection that also takes into account the amplitude of the incident wave.
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7

Félix, Simon, Agnès Maurel, and Jean-François Mercier. "Improved multimodal methods for the acoustic propagation in waveguides with finite wall impedance." Wave Motion 54 (April 2015): 1–10. http://dx.doi.org/10.1016/j.wavemoti.2014.11.007.

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8

Baccouche, Ryan, Soléne Moreau, and Mabrouk Ben Tahar. "Test of single degree of freedom acoustic treatment impedance models for multimodal acoustic propagation in duct with flow." Journal of the Acoustical Society of America 141, no. 6 (2017): 4168–78. http://dx.doi.org/10.1121/1.4983653.

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9

Boucheron, R., H. Bailliet, and J. C. Valiere. "Analytical solution of multimodal acoustic propagation in circular ducts with laminar mean flow profile." Journal of Sound and Vibration 292, no. 3-5 (2006): 504–18. http://dx.doi.org/10.1016/j.jsv.2005.08.017.

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10

Odo, Wataru, Daisuke Kimoto, Makoto Kumon, and Tomonari Furukawa. "Active Sound Source Localization by Pinnae with Recursive Bayesian Estimation." Journal of Robotics and Mechatronics 29, no. 1 (2017): 49–58. http://dx.doi.org/10.20965/jrm.2017.p0049.

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[abstFig src='/00290001/05.jpg' width='300' text='Schematic of the proposed system for actively localizing the sound source' ] Animals use two ears to localize the source of a sound, and this paper considers a robot system that localizes a sound source by using two microphones with active external reflectors that mimic movable pinnae. The body of the robot and the environment both affect the propagation of sound waves, which complicates mapping the acoustic cues to the source. The mapping may be multimodal, and the observed acoustic cues may lead to the incorrect estimation of the locations. In order to achieve sound source localization with such multimodal likelihoods, this paper presents a method for determining a configuration of active pinnae, which uses prior knowledge to optimize their location and orientation, and thus attenuates the effects of pseudo-peaks in the observations. The observations are also adversely affected by noise in the sensor signals, and thus Bayesian inference approach to process them is further introduced. Results of experiments that validate the proposed method are also presented.
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11

Mercier, Jean-François, and Agnès Maurel. "Acoustic propagation in non-uniform waveguides: revisiting Webster equation using evanescent boundary modes." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2156 (2013): 20130186. http://dx.doi.org/10.1098/rspa.2013.0186.

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The scattering of an acoustic wave propagating in a non-uniform waveguide is inspected by revisiting improved multimodal methods in which the introduction of additional modes, so-called boundary modes, allows to better satisfy the Neumann boundary conditions at the varying walls. In this paper, we show that the additional modes can be identified as evanescent modes. Although non-physical, these modes are able to tackle the evanescent part of the field omitted by the truncation and are able to restore the right boundary condition at the walls. In the low-frequency regime, the system can be solved analytically, and the solution for an incident plane wave including one or two boundary modes is shown to be an improvement of the usual Webster equation.
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12

Troian, Renata, Didier Dragna, Christophe Bailly, and Marie-Annick Galland. "Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow." Journal of Sound and Vibration 392 (March 2017): 200–216. http://dx.doi.org/10.1016/j.jsv.2016.10.014.

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13

Mercier, Jean-François, and Agnès Maurel. "Improved multimodal method for the acoustic propagation in waveguides with a wall impedance and a uniform flow." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2190 (2016): 20160094. http://dx.doi.org/10.1098/rspa.2016.0094.

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We present an efficient multimodal method to describe the acoustic propagation in the presence of a uniform flow in a waveguide with locally a wall impedance treatment. The method relies on a variational formulation of the problem, which allows to derive a multimodal formulation within a rigorous mathematical framework, notably to properly account for the boundary conditions on the walls (being locally the Myers condition and the Neumann condition otherwise). Also, the method uses an enriched basis with respect to the usual cosine basis, able to absorb the less converging part of the modal series and thus, to improve the convergence of the method. Using the cosine basis, the modal method has a low convergence, 1/ N , with N the order of truncation. Using the enriched basis, the improvement in the convergence is shown to depend on the Mach number, from 1/ N 5 to roughly 1/ N 1.5 for M =0 to M close to unity. The case of a continuously varying wall impedance is considered, and we discuss the limiting case of piecewise constant impedance, which defines pressure edge conditions at the impedance discontinuities.
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14

Fadden, Christopher, and Sri-Rajasekhar Kothapalli. "A Single Simulation Platform for Hybrid Photoacoustic and RF-Acoustic Computed Tomography." Applied Sciences 8, no. 9 (2018): 1568. http://dx.doi.org/10.3390/app8091568.

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In recent years, multimodal thermoacoustic imaging has demonstrated superior imaging quality compared to other emerging modalities. It provides functional and molecular information, arising due to electromagnetic absorption contrast, at ultrasonic resolution using inexpensive and non-ionizing imaging methods. The development of optical- as well as radio frequency (RF)-induced thermoacoustic imaging systems would benefit from reliable numerical simulations. To date, most numerical models use a combination of different software in order to model the hybrid thermoacoustic phenomenon. Here, we demonstrate the use of a single open source finite element software platform (ONELAB) for photo- and RF-acoustic computed tomography. The solutions of the optical diffusion equation, frequency domain Maxwell’s equations, and time-domain wave equation are used to solve the optical, electromagnetic, and acoustic propagation problems, respectively, in ONELAB. The results on a test homogeneous phantom and an approximate breast phantom confirm that ONELAB is a very effective software for both photo- and RF-acoustic simulations, and invaluable for developing new reconstruction algorithms and hardware systems.
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15

Wilson, Trevor C., Elizabeth A. Silber, Thomas A. Colston, Brian R. Elbing, and Thom R. Edwards. "Bolide Infrasound Signal Morphology and Yield Estimates: A Case Study of Two Events Detected by a Dense Acoustic Sensor Network." Astronomical Journal 169, no. 4 (2025): 223. https://doi.org/10.3847/1538-3881/adbb70.

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Abstract Two bolides (2016 June 2 and 2019 April 4) were detected at multiple regional infrasound stations, with many of the locations receiving multiple detections. Analysis of the received signals was used to estimate the yield, location, and trajectory, as well as the type of shock that produced the received signal. The results from the infrasound analysis were compared with ground-truth information that was collected through other sensing modalities. This multimodal framework offers an expanded perspective on the processes governing bolide shock generation and propagation. The majority of signal features showed reasonable agreement between the infrasound-based interpretation and the other observational modalities, though the yield estimate from the 2019 bolide was significantly lower using the infrasound detections. There was also evidence suggesting that one of the detections was from a cylindrical shock that was initially propagating upward, which is unusual though not impossible.
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16

Bailliet, H., R. Boucheron, J. P. Dalmont, Ph Herzog, S. Moreau, and J. C. Valière. "Setting up an experimental apparatus for the study of multimodal acoustic propagation with turbulent mean flow." Applied Acoustics 73, no. 3 (2012): 191–97. http://dx.doi.org/10.1016/j.apacoust.2011.07.008.

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17

An, Jingge, Chao Pan, and Xiaobo Shi. "Electromagnetic–Mechanical–Acoustic Coupling Analysis of Transformers Under Geomagnetically Induced Current Interference." Machines 13, no. 5 (2025): 437. https://doi.org/10.3390/machines13050437.

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During geomagnetic storms, a geomagnetically induced current (GIC) flows into grounding transformers, potentially causing anomalous vibrations and audible noise in internal components. This study establishes an electromagnetic–mechanical–acoustic coupling (EMAC) model to characterize the multi-physics interactions in transformers under GIC interference. Based on the measured data, the GIC is classified into fluctuating and constant components according to its fluctuation characteristics. A propagation-path-based coupling model is proposed to investigate the correlated interactions among physical fields, extracting critical parameters, including winding current, magnetic flux, electromagnetic force, vibration, and noise. Comparative simulations reveal that the fluctuating component induces more complex multi-physics variations, generating significantly higher vibration amplitudes and noise levels compared to those of the constant component. A dynamic experimental platform is built to obtain multi-physics field information in different modes, and the effectiveness of the model and the correctness of the conclusions are verified through virtual–physical consistency validation. On this basis, multimodal feature information domains are established to delineate the operational state intervals of the transformer under GIC interference. Stability threshold criteria are subsequently developed, providing a critical quantitative basis for the condition monitoring of power transformers.
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18

Kantartzis, Nikolaos V., Theodoros K. Katsibas, Christos S. Antonopoulos, and Theodoros D. Tsiboukis. "A 3D multimodal FDTD algorithm for electromagnetic and acoustic propagation in curved waveguides and bent ducts of varying cross‐section." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 23, no. 3 (2004): 613–24. http://dx.doi.org/10.1108/03321640410540520.

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19

Xu, Tong, Bin Wu, Xiang Gao, Jianfeng Liu, and Xiucheng Liu. "Lamb Wave-Based FDM-PPM Method Data Transmission Scheme in Plate Structures." Sensors 25, no. 6 (2025): 1907. https://doi.org/10.3390/s25061907.

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Lamb wave-based non-electromagnetic communication is an effective solution for real-time information exchange in health monitoring networks of large metallic plate structures. The multimodal nature, dispersive characteristics, and the influence of reflected waves during the propagation of Lamb waves severely limit the duration of communication signals. Within this constrained time, constructing communication signals reasonably is crucial for improving the transmission rate of Lamb wave acoustic data. A coding method based on frequency-division multiplexing–pulse-position modulation (FDM-PPM) is proposed to address the low transmission rate in Lamb wave communication systems. Experimental results demonstrate that the proposed Lamb wave communication system can achieve a maximum transmission rate of up to 50 kbps with a bit error rate as low as 90.7%. Compared with methods using Amplitude-Shift Keying (ASK) and pulse-position modulation (PPM), this method effectively enhances the transmission rate of the Lamb wave communication system while reducing the energy consumption of the excitation signal.
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20

Zaccherini, R., A. Palermo, A. Marzani, A. Colombi, V. K. Dertimanis, and E. N. Chatzi. "Geometric and material attenuation of surface acoustic modes in granular media." Geophysical Journal International 230, no. 1 (2022): 288–97. http://dx.doi.org/10.1093/gji/ggac076.

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SUMMARY Granular materials can be used in laboratory-scale physical models to simulate and study seismic wave propagation in various unconsolidated, porous heterogeneous media. This is due to the diverse available grain configurations, in terms of their shape, size and mechanical parameters, which enable the physical and geological modelling of various complex substrates. In this work, an unconsolidated granular medium, made of silica microbeads, featuring a gravity-induced power-law stiffness profile is experimentally tested in a laboratory setting. The objective is to investigate the attenuation mechanisms of vertically polarized seismic waves traveling at the surface of unconsolidated substrates that are characterized by power-law rigidity profiles. Both geometric spreading and material damping due to skeletal dissipation are considered. The understanding of these two attenuation mechanisms is crucial in seismology for properly determining the seismic site response. An electromagnetic shaker is employed to excite the granular medium between 300 and 550 Hz, generating linear modes that are localized near the surface. A densely sampled section is recorded at the surface using a laser vibrometer. The explicit solution of the geometric attenuation law of Rayleigh-like waves in layered media is employed to calculate the geometric spreading function of the vertically polarized surface modes within the granular material. In accordance with recent studies, the dynamics of these small-amplitude multimodal linear waves can be analysed by considering the granular medium as perfectly continuous and elastic. By performing a nonlinear regression analysis on particle displacements, extracted from experimental velocity data, we determine the frequency-dependent attenuation coefficients, which account for the material damping. The findings of this work show that laboratory-scale physical models can be used to study the geometric spreading of vertically polarized seismic waves induced by the soil inhomogeneity and characterize the material damping of the medium.
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Xu, Kunbo, Zekai Zong, Dongjun Liu, Ran Wang, and Liang Yu. "Deep Learning-Based Sound Source Localization: A Review." Applied Sciences 15, no. 13 (2025): 7419. https://doi.org/10.3390/app15137419.

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As a fundamental technology in environmental perception, sound source localization (SSL) plays a critical role in public safety, marine exploration, and smart home systems. However, traditional methods such as beamforming and time-delay estimation rely on manually designed physical models and idealized assumptions, which struggle to meet practical demands in dynamic and complex scenarios. Recent advancements in deep learning have revolutionized SSL by leveraging its end-to-end feature adaptability, cross-scenario generalization capabilities, and data-driven modeling, significantly enhancing localization robustness and accuracy in challenging environments. This review systematically examines the progress of deep learning-based SSL across three critical domains: marine environments, indoor reverberant spaces, and unmanned aerial vehicle (UAV) monitoring. In marine scenarios, complex-valued convolutional networks combined with adversarial transfer learning mitigate environmental mismatch and multipath interference through phase information fusion and domain adaptation strategies. For indoor high-reverberation conditions, attention mechanisms and multimodal fusion architectures achieve precise localization under low signal-to-noise ratios by adaptively weighting critical acoustic features. In UAV surveillance, lightweight models integrated with spatiotemporal Transformers address dynamic modeling of non-stationary noise spectra and edge computing efficiency constraints. Despite these advancements, current approaches face three core challenges: the insufficient integration of physical principles, prohibitive data annotation costs, and the trade-off between real-time performance and accuracy. Future research should prioritize physics-informed modeling to embed acoustic propagation mechanisms, unsupervised domain adaptation to reduce reliance on labeled data, and sensor-algorithm co-design to optimize hardware-software synergy. These directions aim to propel SSL toward intelligent systems characterized by high precision, strong robustness, and low power consumption. This work provides both theoretical foundations and technical references for algorithm selection and practical implementation in complex real-world scenarios.
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22

Ustinova, Elena S., Vladimir I. Volovach, Tatyana A. Antipova, and Kaira A. Adishirin-Zade. "Reflection of waves from a mobile elastic layer in a multimode waveguide." Physics of Wave Processes and Radio Systems 24, no. 2 (2021): 73–78. http://dx.doi.org/10.18469/1810-3189.2021.24.2.73-78.

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Waveguide structures are used to transmit energy and information signals in a wide range of wavelengths and, in terms of wave-guiding physical properties, usually have mutual (identical) properties in forward and backward directions. The asymmetry of the structure and external influences can often cause non-reciprocity of structures for waves, propagating in mutually opposite directions (this property, although limited, is already used in the so-called nonreciprocal devices of microwave, EHF and optical ranges such as ferrite valves, circulators, phase shifters). At the same time, the nonreciprocal properties of wave-guiding structures, independent of their physical nature, were not considered. It is found, that the motion of the medium filling the acoustic waveguide leads to nonreciprocity of its parameters in the forward and backward directions. The degree of nonreciprocity is proportional to the velocity of the medium. The velocity of the medium also affects the propagation velocity of acoustic waves and leads to a change in the critical frequencies or critical wavelengths of the waveguide modes. As the velocity of the medium increases, the number of modes for which the propagation condition is satisfied increases as well.
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23

Ageykin, Nikita, Vladimir Anisimkin, Andrey Smirnov, et al. "An Electronic “Tongue” Based on Multimode Multidirectional Acoustic Plate Wave Propagation." Sensors 24, no. 19 (2024): 6301. http://dx.doi.org/10.3390/s24196301.

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This paper theoretically and experimentally demonstrates the possibility of detecting the five basic tastes (salt, sweet, sour, umami, and bitter) using a variety of higher-order acoustic waves propagating in piezoelectric plates. Aqueous solutions of sodium chloride (NaCl), glucose (C6H12O6), citric acid (C6H8O7), monosodium glutamate (C5H8NO4Na), and sagebrush were used as chemicals for the simulation of each taste. These liquids differed from each other in terms of their physical properties such as density, viscosity, electrical conductivity, and permittivity. As a total acoustic response to the simultaneous action of all liquid parameters on all acoustic modes in a given frequency range, a change in the propagation losses (ΔS12) of the specified wave compared with distilled water was used. Based on experimental measurements, the corresponding orientation histograms of the ΔS12 were plotted for different types of acoustic waves. It was found that these histograms for different substances are individual and differ in shape, area, and position of their extremes. Theoretically, it has been shown that the influence of different liquids on different acoustic modes is due to both the electrical and mechanical properties of the liquids themselves and the mechanical polarization of the corresponding modes. Despite the fact that the mechanical properties of the used liquids are close to each other, the attenuation of different modes in their presence is not only due to the difference in their electrical parameters. The proposed approach to creating a multi-parametric multimode acoustic electronic tongue and obtaining a set of histograms for typical liquids will allow for the development of devices for the operational analysis of food, medicines, gasoline, aircraft fuel, and other liquid substances without the need for detailed chemical analysis.
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24

Smirnov, Andrey, Vladimir Anisimkin, Natalia Voronova, et al. "Multimode Design and Piezoelectric Substrate Anisotropy Use to Improve Performance of Acoustic Liquid Sensors." Sensors 22, no. 19 (2022): 7231. http://dx.doi.org/10.3390/s22197231.

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Using acoustic wave modes propagation in piezoelectric plates loaded with conductive liquids, peculiarities of the mode-liquid acoustoelectric interaction are studied. It is found that (i) in contrast to bulk and surface acoustic waves propagating in piezoelectric semiconductors, the acoustoelectric attenuation of the modes is not symmetric in respect to its maximum, (ii) a large increase in attenuation may be accompanied by a small decrease in phase velocity and vice versa, (iii) the peculiarities are valid for “pure” (without beam steering) and “not pure” (with beam steering) modes, as well as for modes of different orders and polarizations, and (iv) conductivity of test liquid increases electromagnetic leakage between input and output transducers, affecting results of the measurements. To decrease the leakage, the liquid should be localized between transducers, outside the zone over them. If so, the mode sensitivity may be as large as 8.6 dB/(S/m) for amplitude and 107°/(S/m) for phase. However, because of comparable cross-sensitivity towards viscosity and dielectric permittivity, modes with selective detection of liquid conductivity are not found.
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Lepage, Benoit, and Guillaume Painchard-April. "Acoustic Path Filtering for Improved Multimode Total Focusing Method Inspection." Materials Evaluation 81, no. 2 (2023): 38–45. http://dx.doi.org/10.32548/2023.me-04279.

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Total focusing method (TFM) is an ultrasonic testing (UT) technique that provides nondestructive testing (NDT) inspectors with new imaging modes, enabling more accurate detection, sizing, and representation of challenging defects. While TFM may offer convenient, nearly true-to-geometry imagery as the inspection result, it is often detrimentally affected by mode conversion artifacts. Current standards, such as ASME Section V, place the burden on the inspector to explain the origins of those artifacts, impacting the productivity and reliability of the inspection. A method enabling direct control of the ultrasonic wave propagation modes—that is, transverse wave (T) or longitudinal wave (L)—through each interface of the acoustic path is proposed and evaluated in this paper. This control is achieved after the full matrix capture acquisition by modulating, according to the desired propagation mode, the gain applied on the individual paths within the summation process. This leads to the formation of a Path-Filtered Total Focusing Method image. Empirical results on various use cases show considerable improvement of the signal-to-noise ratio through the almost complete elimination of signals originating from undesired paths.
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26

Ouédraogo, B., R. Maréchal, J. M. Ville, and E. Perrey-Debain. "Broadband noise reduction by circular multi-cavity mufflers operating in multimodal propagation conditions." Applied Acoustics 107 (June 2016): 19–26. http://dx.doi.org/10.1016/j.apacoust.2016.02.001.

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27

Zong, Daoming, and Shiliang Sun. "McOmet: Multimodal Fusion Transformer for Physical Audiovisual Commonsense Reasoning." Proceedings of the AAAI Conference on Artificial Intelligence 37, no. 5 (2023): 6621–29. http://dx.doi.org/10.1609/aaai.v37i5.25813.

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Physical commonsense reasoning is essential for building reliable and interpretable AI systems, which involves a general understanding of the physical properties and affordances of everyday objects, how these objects can be manipulated, and how they interact with others. It is fundamentally a multi-modal task, as physical properties are manifested through multiple modalities, including vision and acoustics. In this work, we present a unified framework, named Multimodal Commonsense Transformer (MCOMET), for physical audiovisual commonsense reasoning. MCOMET has two intriguing properties: i) it fully mines higher-ordered temporal relationships across modalities (e.g., pairs, triplets, and quadruplets); and ii) it restricts the cross-modal flow through the feature collection and propagation mechanism along with tight fusion bottlenecks, forcing the model to attend the most relevant parts in each modality and suppressing the dissemination of noisy information. We evaluate our model on a very recent public benchmark, PACS. Results show that MCOMET significantly outperforms a variety of strong baselines, revealing powerful multi-modal commonsense reasoning capabilities.
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28

Bi, WenPing, Vincent Pagneux, Denis Lafarge, and Yves Aurégan. "An improved multimodal method for sound propagation in nonuniform lined ducts." Journal of the Acoustical Society of America 122, no. 1 (2007): 280–90. http://dx.doi.org/10.1121/1.2736785.

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29

Gentili, G. G., M. Khosronejad, G. Bernasconi, S. Perotto, and S. Micheletti. "Efficient modeling of multimode guided acoustic wave propagation in deformed pipelines by hierarchical model reduction." Applied Numerical Mathematics 173 (March 2022): 329–44. http://dx.doi.org/10.1016/j.apnum.2021.12.008.

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30

Núñez, Ismael, and Carlos Negreira. "Efficiency parameters in time reversal acoustics: Applications to dispersive media and multimode wave propagation." Journal of the Acoustical Society of America 117, no. 3 (2005): 1202–9. http://dx.doi.org/10.1121/1.1856272.

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31

Li, Jing. "Tunable Multimode Filtering of Solid Acoustic Waves in a Three-Component Phononic Crystal Slab." Advanced Materials Research 150-151 (October 2010): 1625–39. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.1625.

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Using of the multiple scattering methods, we characterize the positive and negative multi-refraction and transmission properties of a solid-based phononic crystal composed of coated solid inclusions in view of its applications in tunable multimode filtering. The geometrical parameters are chosen so that a left-handed longitudinal wave mode and a right-handed transverse wave mode, are simultaneously obtained in this three-component phononic crystal. When multimode Gaussian beams are placed transmitting through the phononic crystal slab, both positive and negative refractions are observed. We then study the individual propagation behavior of different modes. The angle dependent transmission beams with different energy distributions are found at the other side of the slab. Transmitted transverse waves coming from different directions incidence finally walk together into four oriented beams. Meanwhile, longitudinal wave incidence with different directions behaves simply as negative refraction in the slab. A far-field longitudinal wave image can be achieved being excited by a longitudinal wave point source. The three-component phononic crystal slab thus can be served as an alternate in tunable multimode filtering devices.
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32

Guennoc, Thomas, Jean-Baptiste Doc, and Simon Félix. "Improved multimodal formulation of the wave propagation in a 3D waveguide with varying cross-section and curvature." Journal of the Acoustical Society of America 149, no. 1 (2021): 476–86. http://dx.doi.org/10.1121/10.0003336.

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33

Sugimoto, Rie, R. Jeremy Astley, Claire R. McAleer, and Iansteel Achunche. "A numerical study on multimode sound propagation in lined ducts and radiation to the far field." Journal of the Acoustical Society of America 123, no. 5 (2008): 3128. http://dx.doi.org/10.1121/1.2933070.

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34

Bauer, Adam Q., Christian C. Anderson, Karen R. Marutyan, et al. "Experimental confirmation of negative dispersion and Bayesian inversion of multimode propagation in a bone‐mimicking phantom." Journal of the Acoustical Society of America 123, no. 5 (2008): 3512. http://dx.doi.org/10.1121/1.2934415.

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35

Alleyne, D., and P. Cawley. "A two-dimensional Fourier transform method for the measurement of propagating multimode signals." Journal of the Acoustical Society of America 89, no. 3 (1991): 1159–68. http://dx.doi.org/10.1121/1.400530.

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36

Yang, Minye, Zhilu Ye, Mohamed Farhat, and Pai-Yen Chen. "Cascaded PT-symmetric artificial sheets: multimodal manipulation of self-dual emitter-absorber singularities, and unidirectional and bidirectional reflectionless transparencies." Journal of Physics D: Applied Physics 55, no. 8 (2021): 085301. http://dx.doi.org/10.1088/1361-6463/ac3300.

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Abstract We introduce cascaded parity-time (PT)-symmetric artificial sheets (e.g. metasurfaces or frequency selective surfaces) that may exhibit multiple higher-order laser-absorber modes and bidirectional reflectionless transmission resonances within the PT-broken phase, as well as a unidirectional reflectionless transmission resonance associated with the exceptional point (EP). We derive the explicit expressions of the gain–loss parameter required for obtaining these modes and their intriguing physical properties. By exploiting the cascaded PT structures, the gain–loss threshold for the self-dual laser-absorber operation can be remarkably lowered, while the EP remains unaltered. We further study interferometric sensing based on such a multimodal laser-absorber and demonstrate that its sensitivity may be exceptionally high and proportional to the number of metasurfaces along the light propagation direction.
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37

Raghavan, Ajay, and Carlos E. S. Cesnik. "3-D Elasticity-Based Modeling of Anisotropic Piezocomposite Transducers for Guided Wave Structural Health Monitoring." Journal of Vibration and Acoustics 129, no. 6 (2007): 739–51. http://dx.doi.org/10.1115/1.2748776.

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Anisotropic piezocomposite transducers (APTs), such as macro fiber composites and active fiber composites, have great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. Their main advantages over conventional monolithic piezoceramic wafer transducers are mechanical flexibility, curved surface conformability, power efficiency, their ability to excite focused GW fields, and their unidirectional sensing capability as a GW sensor. In this paper, models are developed to describe excitation of GW fields by APTs in isotropic structures. The configurations explored are plane Lamb-wave fields in beams with rectangular cross-section, axisymmetric GW fields in cylinders, and 3-D GW fields in plates. The dynamics of the substrate and transducer are assumed uncoupled. The actuator is modeled as causing shear traction at the edges of the actuator’s active area along the fiber direction. The sensor is modeled as sensing the average extensional strain over the active area along the fiber direction. The work is unique in that the formulation is based on 3-D elasticity, and no reduced-order structural assumptions are used. This is crucial to model multimodal GW propagation, especially at high frequencies. A formulation is also proposed to model the behavior of APTs as GW sensors. Finally, results from experimental tests to examine the validity of the models are discussed and the possible sources of error are examined in detail.
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Kauffmann, Pierre, Marie-Aude Ploix, Jean-François Chaix, Cécile Gueudre, Gilles Corneloup, and François Baque. "Interferences in the re-emission field of multimodal leaky lamb waves propagating in an immersed plate: Analytical modelling, simulation and experimentation." Journal of Sound and Vibration 465 (January 2020): 115015. http://dx.doi.org/10.1016/j.jsv.2019.115015.

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39

Mangin, Bruno, Majd Daroukh, and Gwénaël Gabard. "Propagation of Acoustic Waves in Ducts with Flow Using the Multimodal Formulation." AIAA Journal, March 1, 2023, 1–13. http://dx.doi.org/10.2514/1.j062659.

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This paper presents a multimodal method for the computation of the acoustic field in an axisymmetric varying duct with or without liner and in the presence of mean flow. The original three-dimensional equations are rearranged into a set of coupled one-dimensional equations by projecting the acoustic field over transverse basis functions. To maintain the computational efficiency of the original multimodal method (applicable without flow), only the leading-order effects of the mean flow are modeled using a multiple-scales approach. A matching procedure is also given to deal with liner discontinuities in such a duct. Two different transverse bases are used: one is based on Fourier–Bessel functions to evaluate the effect of modal scattering and the other is based on Fourier–Chebyshev polynomials to improve the method efficiency. The formulation is evaluated against analytical models based on the Wentzel–Kramers–Brillouin technique and against finite-element solutions. It is shown to give consistent results for minor computational cost for modes propagating in ducts with or without acoustic liners. This method can be easily adapted to take into account more complex flows and geometries.
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40

Sánchez-Orgaz, Eva María, Francisco David Denia, Jose Martínez-Casas, and Javier Carballeira. "Computational approach for the acoustic modelling of large aftertreatment devices with multimodal incident sound fields." Advances in Mechanical Engineering 15, no. 9 (2023). http://dx.doi.org/10.1177/16878132231199870.

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The influence of multimodal incident sound fields on the acoustic behaviour of large aftertreatment devices incorporating a monolith is modelled and analysed in detail. The analytical mode matching method is applied to the compatibility conditions of the three-dimensional acoustic fields at the device geometric discontinuities, leading to the computation of the complex wave amplitudes in all the subdomains involved and the corresponding device transmission loss. To have a realistic model, three-dimensional propagation must be considered in the inlet/outlet ducts and chambers, while one-dimensional wave propagation has to be assumed along the small capillaries of the aftertreatment device monolith (such catalytic converters and particulate filters); therefore, the monolith can be replaced by a plane wave four-pole transfer matrix from an acoustical point of view. On the other hand, for large aftertreatment device inlet ducts such as those found in heavy-duty and off-road engines, the usual models with plane incident wave excitation are not accurate since the onset of higher order incident modes in the inlet duct is expected for the frequency range of interest. Therefore, a variation of the acoustic attenuation performance is likely to occur depending on these modes, similar to the results previously found in the case of large dissipative silencers. Results are presented for three different multimodal incident sound field hypotheses: equal modal amplitude, equal modal power and equal modal energy density. A relevant influence on the sound attenuation is found for the test problems considered in the current investigation.
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41

Song, Xiang, Jingjian Xu, Tianyue Yuan, et al. "An investigation on the modelling of a finite porous liner for the sound propagation in a rectangular duct." Journal of Vibration and Control, December 26, 2022, 107754632211477. http://dx.doi.org/10.1177/10775463221147734.

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Acoustic liners take an essential role in the noise attenuation in ducts. In this work, the multimodal method based on the finite-difference method is extended to predict the acoustic field in a rectangular duct lined with a finite porous material and validated by the experiment. A modified immersed interface method is developed for the air–porous interface problem in the extended multimodal method without flow. When the flow exists, the treatments of the air–porous interface problem and the continuity of pressure between the wall and liner are also given. Three ways of describing the porous liner using the surface impedance at normal incidence named normal impedance, the surface impedance at grazing incidence named shear impedance and a cavity filled with the equivalent fluid of porous material are introduced. The comparison among the three ways reveals that the extended method of treating liners using a cavity filled with the equivalent fluid is more accurate for the acoustic evaluation of porous liners. The analysis finds that the shear impedance can reasonably present the influence of porous material during the comparisons of transmission loss curves of the liners with different lengths and depths at different Mach numbers. In most cases, the prediction by the shear impedance is closer to that simulated by the cavity filled with porous material than the normal impedance. Normal impedance is hardly utilized to describe the porous material and is only reliable when the cavity is very short and deep.
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42

Yddal, Torstein, Spiros Kotopoulis, Odd Helge Gilja, and Michiel Postema. "Ultrasound transducers with an optical window." June 17, 2014. https://doi.org/10.5281/zenodo.4891808.

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Ultrasound is one of the most cost-effective deep tissue clinical imaging modalities. Near all ultrasound transducers are fabricated from piezoelectric materials that require metal surface electrodes, making the transducers opaque. With the increasing need for multi-modal and compact imaging and therapeutic tools new transducers fabrication techniques need to be evaluated. In our work we evaluate several designs that allow a large optical window in combination with ultrasonic propagation collinear to the imaging path. Three types of transducers were made based on a stacked design, in two different sizes. The optical windows were 20-mm and 10-mm with outer diameters of 50-mm and 38-mm respectively. The devices were characterised for acoustic bandwidth and sensitivity using a pulse receive technique. The acoustic power was measured using a custom made radiation force balance. The beam profile was measured using a three-dimensional scanning chamber with a mobile needle-hydrophone. The transient response waveform of a burst wave was captured using the needle hydrophone, and an FFT was performed to get the power spectrum to determine the linearity of the ultrasound generation of the transducer. The frequency response showed that these transducers had a large FWHM bandwidth of 56%. The field scans showed that the acoustic propagation pattern was very similar to traditional ultrasound transducers, yet the different constructions affected the focal distance and sidelobes. In addition surface scans, indicated that in all transducers glass window acted like an oscillating diaphragm generating ultrasound. The acoustic power measurements indicated that these devices could exceed acoustic powers of 16 W. Traditional ultrasonic imaging only requires several milliwatts whereas therapeutic application only require several watts. These transducers indicate their potential for multimodal imaging and therapy for example combining endoscopy with ultrasound surgery, or simultaneous ultrasound and bioluminescence imaging.
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43

Liou, Yi-Ting, Madeleine Msall, Alberto Hernández-Mínguez, and Paulo Ventura Santos. "Spatial analysis of multi-frequency SAW beams excited by slanted IDTs on ZnO-SiC heterostructures." Journal of Physics D: Applied Physics, July 8, 2024. http://dx.doi.org/10.1088/1361-6463/ad600e.

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Abstract Slanted (or fan-shaped) interdigital transducers (IDTs) with broadband response allow the selective excitation of surface acoustic waves (SAWs) with narrow beam widths and pathways controlled by the excitation frequency. Such SAW-based spatial and frequency control is important for applications in microfluidics, as well as in emerging applications in semiconductor nanostructures. In this contribution, we generate both Rayleigh and Sezawa modes with slanted IDTs on a 4H-SiC substrate coated with a piezoelectric ZnO film. We directly measure the phase wavefronts of narrow SAW beams in the 1200-1260 MHz frequency bandwidth using high-resolution (<1 μm) optical interferometry, and discuss the mechanisms that directly affect the propagation direction and phase profiles of the SAW beams. The combination of multimodal and multi-frequency SAW delay lines provides rich opportunities for SAW-based control of low-dimensional systems, such as electrons in epitaxial graphene or spin centers near the surface of the SiC substrates.
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44

Wei Wei, Feng Guan, and Xin Fang. "The Integrated Vibration Absorption and Isolation Design Method for Metamaterial Beams Based on Bandgap wave-insulating Vibration Isolatior." Acta Physica Sinica, 2024, 0. http://dx.doi.org/10.7498/aps.73.20241135.

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Advanced vibration control technologies are in high demand for equipment such as aircraft and ships. Currently, most systems separate vibration absorption and isolation design, and existing isolation designs cannot effectively enhance the isolation of low-frequency line spectra. There is an urgent need to develop integrated vibration absorption and isolation designs and enhance low-frequency line spectrum control. In response to this need, this paper focuses on a typical Euler beam and investigates the propagation characteristics of vibrations in both transverse and longitudinal directions, the principles of integrated vibration absorption and isolation design, and the synergistic regulation of bandgaps, based on acoustic metamaterial bandgap wave-insulating vibration control configurations and analytical methods. Ultimately, without adding additional structures, the use of wave-insulating vibration control devices generates multiple modes of vibration absorption and isolation simultaneously, achieving an integrated low-frequency, broadband, and high-efficiency vibration absorption and isolation design. In the transverse vibration isolation pathway, this method achieves broadband vibration isolation while introducing localized resonant bandgaps that significantly enhance low-frequency vibration isolation. In the longitudinal (forward propagation) pathway, in addition to near-zero and Bragg bandgaps, multilayer isolators generate multimodal local resonant bandgaps, achieving low-frequency broadband vibration absorption and effective control across the entire frequency range. This paper elucidates the synergistic modulation of longitudinal and transverse bandgaps, showing that by superimposing these bandgaps, an impressive bandgap ratio of 87.3% below 100 Hz across the entire frequency range can be achieved. Furthermore, an entity structure was designed, and the accuracy of the analytical results was verified using the finite element method. The findings provide feasible design ideas for the integrated vibration absorption and isolation of complex structures such as beams, plates, pipelines, and frames.
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45

Prasad, Rajan, and Abhijit Sarkar. "Broadband Seismic Isolation of Periodic Ladder Frame Structure." Journal of Vibration and Acoustics 143, no. 1 (2020). http://dx.doi.org/10.1115/1.4047704.

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Abstract Ladder frame structures are used as models for multistorey buildings. These periodic structures exhibit alternating propagating and attenuating frequency bands. Of the six different wave modes of propagation, two modes strongly attenuate at all frequencies. The other four modes have nonoverlapping stop band characteristics. Thus, it is challenging to isolate such structures when subjected to broadband, multimodal base excitation. In this study, we seek to synthesize a periodic ladder frame structure that has attenuation characteristics over the maximal range of frequencies for all the modes of wave propagation. We synthesize a unit cell of the periodic structure, which comprises two distinct regions having different inertial, stiffness, and geometric properties. The eigenvalues of the transfer matrix of the unit cell determines the attenuating or the nonattenuating characteristics of the structure. A novel pictorial presentation in the form of eigenvalue map is developed. This is used to synthesize the optimal unit cell. Also, design guidelines for suitable selection of the design parameters are presented. It is shown that a large finite periodic structure comprising a unit cell synthesized using the present approach has significantly better isolation characteristics in comparison to the homogeneous or any other arbitrarily chosen periodic structure.
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46

Hojo, Emi, Wiraphong Sucharit, Saranya Jaruchainiwat, et al. "Magnetic Resonance Elastography of Upper Trapezius Muscle." NMR in Biomedicine 38, no. 4 (2025). https://doi.org/10.1002/nbm.70007.

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ABSTRACTThe goal of the present study was to investigate the effect of positioning a soft flexible tube‐based actuator parallel or orthogonal to the principle muscle fibre direction, on measurements of the stiffness of upper trapezius (UT) muscle obtained using magnetic resonance elastography (MRE). The effects of using three different vibration frequencies (60 Hz, 80 Hz and 100 Hz) and studying left and right sides of the body were also investigated. The relevant MRE datasets were acquired on a 1.5 T MRI system using a 2D gradient‐echo (GRE) MRE sequence, and corresponding wave images produced using multimodel direct inversion (MMDI) were analysed by two observers using the manual caliper technique. Except for two of the 108 individual datasets, when the agreement was moderate, there was substantial to perfect agreement between wave quality scores obtained by the two observers, with an identical mean value. Similarly, and again with only two exceptions, there was good to excellent agreement between the measurements of UT stiffness obtained by the two observers. UT stiffness values obtained when the acoustic waves were propagating along the principle muscle fibre direction were significantly higher than when the waves were propagating orthogonal to the principle muscle fibre direction at all vibration frequencies (p < 0.005), and only for the former was a significant dispersion effect observed whereby stiffness increased as frequency increased (p < 0.05). No significant asymmetry was observed in measurements of UT stiffness obtained for the left and right sides of the body (p = 0.29). In conclusion, the new soft and flexible tube‐based actuator is comfortable and produced very good wave propagation in UT when positioned in either orientation. However, it is recommended for wave propagation to be induced in the principle fibre direction and there was found to be no advantage in using a vibration frequency above 60 Hz.
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47

Dawidowski, David, Richard Nauber, Lars Büttner, and Jürgen Czarske. "Time reversal ultrasound focusing through multimode waveguides." tm - Technisches Messen 84, no. 9 (2017). http://dx.doi.org/10.1515/teme-2016-0062.

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AbstractUltrasound imaging in harsh environments, such as the continuous steel casting process, benefits from a spatial separation of sensors and measuring volume to avoid damaging e.g. because of high temperatures. This can be achieved through acoustical multimode waveguides. To focus ultrasound in the measuring volume despite the complex sound propagation, we propose using the time reversal technique. We present numerical simulations and experiments using the phased array ultrasound Doppler velocimeter to focus through a water filled waveguide with a 64 element array. A resolution in the millimetre range is achieved for a 68 mm long waveguide.
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48

Liu, Lei, Xiujuan Zhang, Ming‐Hui Lu, and Yan‐Feng Chen. "Width‐Independent and Robust Multimode Interference Waveguides Based on Anomalous Bulk States." Laser & Photonics Reviews, May 29, 2025. https://doi.org/10.1002/lpor.202500943.

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AbstractMultimode interference (MMI) underpins critical functionalities in wave splitting, filtering, switching, and multiplexing. Conventional MMI waveguides, however, suffer from instability due to their high dependence on waveguide dimensions, particularly the width. Here, width‐independent and robust MMI waveguides using graphene‐inspired Dirac metamaterials are realized. Leveraging lattice symmetry, these materials support anomalous bulk states with uniform wavefunctions through boundary modulation, independent of sample size and robust against material perturbations. Stacking multiple layers of such materials in a waveguide generates vertical MMI that inherits width independence and defect immunity. Experimentally, a 2 × 2 MMI acoustic power splitter is demonstrated. Self‐images of an input field are observed at periodic intervals along the propagation direction, with the output power split at an arbitrary splitting ratio controlled by frequency. Remarkably, the MMI maintains stability across multiple waveguides with stepped widths, exhibiting high‐coupling efficiency. Extending to optics, a silicon‑based design is proposed, and photonic anomalous bulk states and width‐independent, stable optical MMI at telecom wavelength (≈1550 nm) are numerically validated. This approach decouples multimode‐interference from waveguide dimensions, redistributing power in the vertical direction while freeing the lateral dimension, which is advantageous for compact, high‐efficiency, and fabrication‐tolerant MMI devices.
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49

Joglekar, D. M. "Scattering of the Fundamental Lamb Modes in Bent Metallic Plates." Journal of Applied Mechanics, September 15, 2022, 1–32. http://dx.doi.org/10.1115/1.4055619.

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Abstract Guided elastic waves, propagating through curved waveguides, have attracted significant attention in the recent past; both from the perspectives of assessment of structural integrity and generating novel designs of acoustic waveguides. This paper presents investigation of the interaction of the fundamental Lamb modes with a cylindrical bend in thin metallic plates. A hybrid numerical method is exposited which combines the computational efficacy of the Semi Analytical Finite Element method in modeling the long straight portions of the plate and the versatility of the conventional Finite Element method in modeling the bent portion. The predictive capabilities of the proposed method are validated using transient finite element simulations. Appropriate modifications to the hybrid method, needed for simulating the multimodal incidence resulting from the point-force actuation, are discussed. Using the hybrid method, the scattering and mode-conversion behavior, imparted by the cylindrical bend, is studied when the two fundamental Lamb modes are used as the incident interrogation signals. The extents of equi-modal and cross-modal contributions in both; the reflected as well as transmitted waveforms are quantified in terms of the respective modal energy ratios. Explicable contour charts are presented for comprehending the scattering behavior over a wide range of frequencies and bend angles that span from zero degrees to 180 degrees. For two representative cases the modal displacement patterns inside the bend region are presented and discussed. The present investigation can find its potential use in the analysis of geometrically irregular structures leading to the design of novel acoustic waveguides.
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50

Baker, Janet M., and Peter Cariani. "Time-domain brain: temporal mechanisms for brain functions using time-delay nets, holographic processes, radio communications, and emergent oscillatory sequences." Frontiers in Computational Neuroscience 19 (February 18, 2025). https://doi.org/10.3389/fncom.2025.1540532.

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Time is essential for understanding the brain. A temporal theory for realizing major brain functions (e.g., sensation, cognition, motivation, attention, memory, learning, and motor action) is proposed that uses temporal codes, time-domain neural networks, correlation-based binding processes and signal dynamics. It adopts a signal-centric perspective in which neural assemblies produce circulating and propagating characteristic temporally patterned signals for each attribute (feature). Temporal precision is essential for temporal coding and processing. The characteristic spike patterns that constitute the signals enable general-purpose, multimodal, multidimensional vectorial representations of objects, events, situations, and procedures. Signals are broadcast and interact with each other in spreading activation time-delay networks to mutually reinforce, compete, and create new composite patterns. Sequences of events are directly encoded in the relative timings of event onsets. New temporal patterns are created through nonlinear multiplicative and thresholding signal interactions, such as mixing operations found in radio communications systems and wave interference patterns. The newly created patterns then become markers for bindings of specific combinations of signals and attributes (e.g., perceptual symbols, semantic pointers, and tags for cognitive nodes). Correlation operations enable both bottom-up productions of new composite signals and top-down recovery of constituent signals. Memory operates using the same principles: nonlocal, distributed, temporally coded memory traces, signal interactions and amplifications, and content-addressable access and retrieval. A short-term temporary store is based on circulating temporal spike patterns in reverberatory, spike-timing-facilitated circuits. A long-term store is based on synaptic modifications and neural resonances that select specific delay-paths to produce temporally patterned signals. Holographic principles of nonlocal representation, storage, and retrieval can be applied to temporal patterns as well as spatial patterns. These can automatically generate pattern recognition (wavefront reconstruction) capabilities, ranging from objects to concepts, for distributed associative memory applications. The evolution of proposed neural implementations of holograph-like signal processing and associative content-addressable memory mechanisms is discussed. These can be based on temporal correlations, convolutions, simple linear and nonlinear operations, wave interference patterns, and oscillatory interactions. The proposed mechanisms preserve high resolution temporal, phase, and amplitude information. These are essential for establishing high phase coherency and determining phase relationships, for binding/coupling, synchronization, and other operations. Interacting waves can sum constructively for amplification, or destructively, for suppression, or partially. Temporal precision, phase-locking, phase-dependent coding, phase-coherence, synchrony are discussed within the context of wave interference patterns and oscillatory interactions. Sequences of mixed neural oscillations are compared with a cascade of sequential mixing stages in a single-sideband carrier suppressed (SSBCS) radio communications system model. This mechanism suggests a manner by which multiple neural oscillation bands could interact to produce new emergent information-bearing oscillation bands, as well as to abolish previously generated bands. A hypothetical example illustrates how a succession of different oscillation carriers (gamma, beta, alpha, theta, and delta) could communicate and propagate (broadcast) information sequentially through a neural hierarchy of speech and language processing stages. Based on standard signal mixing principles, each stage emergently generates the next. The sequence of oscillatory bands generated in the mixing cascade model is consistent with neurophysiological observations. This sequence corresponds to stages of speech-language processing (sound/speech detection, acoustic-phonetics, phone/clusters, syllables, words/phrases, word sequences/sentences, and concepts/understanding). The oscillatory SSBCS cascade model makes specific predictions for oscillatory band frequencies that can be empirically tested. The principles postulated here may apply broadly for local and global oscillation interactions across the cortex. Sequences of oscillatory interactions can serve many functions, e.g., to regulate the flow and interaction of bottom-up, gamma-mediated and top-down, beta-mediated neural signals, to enable cross-frequency coupling. Some specific guidelines are offered as to how the general time-domain theory might be empirically tested. Neural signals need to be sampled and analyzed with high temporal resolution, without destructive windowing or filtering. Our intent is to suggest what we think is possible, and to widen both the scope of brain theory and experimental inquiry into brain mechanisms, functions, and behaviors.
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