Journal articles: 'Acoustic field effects'

1

Xu, Guo Liang, Qi Wei He, Shao Chun Ding, and Hai Bo Wan. "Effects of Quay Wall and Seabed Reflection on the AUV Acoustic Radiation Test Analysis." Applied Mechanics and Materials 599-601 (August 2014): 922–26. http://dx.doi.org/10.4028/www.scientific.net/amm.599-601.922.

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To analyze effects of quay environment on the AUV radiated acoustic field test, the PNAH (PNAH: planar near-field acoustical holography) was used to simulate acoustic field. By simulating the free and non-free acoustic field and comparing amplitudes and angles of complex sound pressure, Analyze effects of quay wall and seabed reflection on the AUV radiated acoustic field test to determine the standard of quay wall and seabed environment which meets testing. The work would provide a certain reference for the AUV radiated acoustic field test.

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Bálek, R., M. Červenka, and S. Pekárek. "Acoustic field effects on a negative corona discharge." Plasma Sources Science and Technology 23, no. 3 (May 15, 2014): 035005. http://dx.doi.org/10.1088/0963-0252/23/3/035005.

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Walker, John S., Gita Talmage, Samuel H. Brown, and Neal A. Sondergaard. "Acoustic End Effects in Magnetohydrodynamic Submerged Vehicular Propulsors." Journal of Ship Research 36, no. 01 (March 1, 1992): 69–76. http://dx.doi.org/10.5957/jsr.1992.36.1.69.

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This paper treats the effects near the ends of the channel on the transmission and reflection of periodic acoustic waves generated at some cross section inside a magnetohydrodynamic (MHD) seawater propulsion system. A region of high uniform magnetic field inside the MHD submerged vehicular propulsor is separated from the essentially zero magnetic field outside the channel by a nonuniform, fringing magnetic field at each end of the channel. The channel configuration chosen here is that of a straight, rectangular duct with electrically insulating top and bottom walls perpendicular to the magnetic field and highly conducting sidewalls parallel to the field. In particular, the mathematical analysis focuses on determining the percentage of the incident wave which is reflected by the fringing-field region back into the uniform-field region and the percentage which is transmitted through the fringing-field region into the zero-field region. The key parameter is the acoustic interaction parameter N, which is the characteristic ratio of the electromagnetic body force opposing motions across magnetic field lines to the inertial "force" in the acoustic wave. Solutions are presented for the fundamental, plane acoustic mode for arbitrary values of Ν and for all acoustic modes for Ν < 1. The amplitudes of the reflected and transmitted waves depend on the wave frequency, the length of the fringing-field region, N, and the type of wave mode. The magnetic field introduces a strong anisotropy with strong damping of modes involving transverse motions across magnetic field lines and with weak damping of modes involving transverse motions along field lines. This is the third in a series of articles on MHD marine propulsion from the David Taylor Research Center MHD propulsion program [Brown et al (1990), Tempelmeyer (1990)].

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ARIAS, E., C. H. G. BÉSSA, and N. F. SVAITER. "AN ANALOG FLUID MODEL FOR SOME TACHYONIC EFFECTS IN FIELD THEORY." Modern Physics Letters A 26, no. 31 (October 10, 2011): 2335–44. http://dx.doi.org/10.1142/s0217732311036784.

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We consider the sound radiation from an acoustic point-like source moving along a supersonic ("space-like") trajectory in a fluid at rest. We call it an acoustic "tachyonic" source. We describe the radiation emitted by this supersonic source. After quantizing the acoustic perturbations, we present the distribution of phonons generated by this classical tachyonic source and the classical wave interference pattern.

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BAILLOT, F., J. B. BLAISOT, G. BOISDRON, and C. DUMOUCHEL. "Behaviour of an air-assisted jet submitted to a transverse high-frequency acoustic field." Journal of Fluid Mechanics 640 (December 2, 2009): 305–42. http://dx.doi.org/10.1017/s002211200999139x.

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Acoustic instabilities with frequencies roughly higher than 1 kHz remain among the most harmful instabilities, able to drastically affect the operation of engines and even leading to the destruction of the combustion chamber. By coupling with resonant transverse modes of the chamber, these pressure fluctuations can lead to a large increase of heat transfer fluctuations, as soon as fluctuations are in phase. To control engine stability, the mechanisms leading to the modulation of the local instantaneous rate of heat release must be understood. The commonly developed global approaches cannot identify the dominant mechanism(s) through which the acoustic oscillation modulates the local instantaneous rate of heat release. Local approaches are being developed based on processes that could be affected by acoustic perturbations. Liquid atomization is one of these processes. In the present paper, the effect of transverse acoustic perturbations on a coaxial air-assisted jet is studied experimentally. Here, five breakup regimes have been identified according to the flow conditions, in the absence of acoustics. The liquid jet is placed either at a pressure anti-node or at a velocity anti-node of an acoustic field. Acoustic levels up to 165 dB are produced. At a pressure anti-node, breakup of the liquid jet is affected by acoustics only if it is assisted by the coaxial gas flow. Effects on the liquid core are mainly due to the unsteady modulation of the annular gas flow induced by the acoustic waves when the mean dynamic pressure of the gas flow is lower than the acoustic pressure amplitude. At a velocity anti-node, local nonlinear radiation pressure effects lead to the flattening of the jet into a liquid sheet. A new criterion, based on an acoustic radiation Bond number, is proposed to predict jet flattening. Once the sheet is formed, it is rapidly atomized by three main phenomena: intrinsic sheet instabilities, Faraday instability and membrane breakup. Globally, this process promotes atomization. The spray is also spatially organized under these conditions: large liquid clusters and droplets with a low ejection velocity can be brought back to the velocity anti-node plane, under the action of the resulting radiation force. These results suggest that in rocket engines, because of the large number of injectors, a spatial redistribution of the spray could occur and lead to inhomogeneous combustion producing high-frequency combustion instabilities.

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Martinelli, Sheri, and Charles Holland. "Effects of seabed curvature on the scattered acoustic field." Journal of the Acoustical Society of America 139, no. 4 (April 2016): 2168. http://dx.doi.org/10.1121/1.4950432.

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Golak, Slawomir, and Roman Przylucki. "Modeling Acoustic Effects During Casting Nanocomposites Under Electromagnetic Field." IEEE Transactions on Magnetics 50, no. 2 (February 2014): 289–92. http://dx.doi.org/10.1109/tmag.2013.2279273.

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Sarıgül, A. Saide, and Erkan Karagözlü. "Vibro-acoustic coupling in composite plate-cavity systems." Journal of Vibration and Control 24, no. 11 (January 10, 2017): 2274–83. http://dx.doi.org/10.1177/1077546316685209.

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Composite materials are extensively utilized today as strategic products. Although this widespread use, their vibro-acoustics characteristics have not been examined extensively. Specifically, the interactive coupling between the vibration and acoustics of composite plate- cavity systems is an untapped field. In this paper, the results of a modal structural-acoustic coupling analysis for plates with different composite parameters are presented. Natural frequencies of the coupled systems are tabulated. The effects of material, ply angle and number of layers on the coupled vibro-acoustic characteristics of composite plate-cavity systems have been examined and compared with the behaviour of isotropic plate systems.

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Ye, S. G., X. F. Gong, and X. Z. Liu. "Nonlinear effects on acoustic field measurement in biomedical frequency range." Journal of the Acoustical Society of America 99, no. 4 (April 1996): 2539–74. http://dx.doi.org/10.1121/1.415832.

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Qu, Xiaopeng, and Huihe Qiu. "Thermal Bubble Dynamics Under the Effects of an Acoustic Field." Heat Transfer Engineering 32, no. 7-8 (June 2011): 636–47. http://dx.doi.org/10.1080/01457632.2010.509757.

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FILHO, FERNANDO FACHINI. "The Effects of the Acoustic Field On Droplet Extinction Processes." Combustion Science and Technology 120, no. 1-6 (November 1996): 237–53. http://dx.doi.org/10.1080/00102209608935575.

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Voloshin, V. V. "Near-field simulation of acoustic effects in tire tread cavities." Computational Mathematics and Modeling 19, no. 3 (July 2008): 248–62. http://dx.doi.org/10.1007/s10598-008-9001-2.

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13

Song, Ailing, Tianning Chen, Xiaopeng Wang, Yanhui Xi, and Qingxuan Liang. "Underwater unidirectional acoustic transmission through a plate with bilateral asymmetric gratings." Modern Physics Letters B 32, no. 11 (April 18, 2018): 1850133. http://dx.doi.org/10.1142/s0217984918501336.

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In this paper, a novel underwater unidirectional acoustic transmission (UAT) device consisting of a plate with bilateral asymmetric gratings is proposed and numerically investigated. The transmission spectra, the acoustic intensity field distributions, and the displacement field distributions are numerically calculated based on the finite element method. The transmission spectra show that the proposed device exhibits different UAT effects in three bands. The acoustic intensity field distributions demonstrate that the proposed device can realize UAT, which agree well with the transmission spectra. The mechanism is discussed by analyzing the displacement field distributions, and the UAT is attributed to the symmetric mode excited in brass plate. Furthermore, the effects of the lattice constant, the upper slit width, and the lower slit width on bands are discussed. Our design provides a good reference for designing underwater UAT devices and has potential applications in some fields, such as medical ultrasonic devices, acoustic barrier, and noise insulation.

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Ge, Hao, Min Yang, Chu Ma, Ming-Hui Lu, Yan-Feng Chen, Nicholas Fang, and Ping Sheng. "Breaking the barriers: advances in acoustic functional materials." National Science Review 5, no. 2 (December 26, 2017): 159–82. http://dx.doi.org/10.1093/nsr/nwx154.

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Abstract Acoustics is a classical field of study that has witnessed tremendous developments over the past 25 years. Driven by the novel acoustic effects underpinned by phononic crystals with periodic modulation of elastic building blocks in wavelength scale and acoustic metamaterials with localized resonant units in subwavelength scale, researchers in diverse disciplines of physics, mathematics, and engineering have pushed the boundary of possibilities beyond those long held as unbreakable limits. More recently, structure designs guided by the physics of graphene and topological electronic states of matter have further broadened the whole field of acoustic metamaterials by phenomena that reproduce the quantum effects classically. Use of active energy-gain components, directed by the parity–time reversal symmetry principle, has led to some previously unexpected wave characteristics. It is the intention of this review to trace historically these exciting developments, substantiated by brief accounts of the salient milestones. The latter can include, but are not limited to, zero/negative refraction, subwavelength imaging, sound cloaking, total sound absorption, metasurface and phase engineering, Dirac physics and topology-inspired acoustic engineering, non-Hermitian parity–time synthetic active metamaterials, and one-way propagation of sound waves. These developments may underpin the next generation of acoustic materials and devices, and offer new methods for sound manipulation, leading to exciting applications in noise reduction, imaging, sensing and navigation, as well as communications.

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15

O'Brien, R. W. "Electro-acoustic effects in a dilute suspension of spherical particles." Journal of Fluid Mechanics 190 (May 1988): 71–86. http://dx.doi.org/10.1017/s0022112088001211.

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Sound waves can be generated in a colloid by the application of an alternating electric field. In this paper we describe the method for calculating this and the related electro-acoustic phenomenon of electric fields generated by sound waves. As an illustration of the procedure, we obtain formulae for these two effects for a suspension of spherical particles with thin double layers, in a parallel plate geometry.

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Prasad, Anil, and Dilip Prasad. "Unsteady Aerodynamics and Aeroacoustics of a High-Bypass Ratio Fan Stage." Journal of Turbomachinery 127, no. 1 (January 1, 2005): 64–75. http://dx.doi.org/10.1115/1.1811103.

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A numerical investigation of the unsteady aerodynamics of a fan stage comprised of a transonic rotor, swept fan exit guide vane (FEGV), and low-pressure compressor inlet guide vane (IGV) is described, with emphasis on acoustics. It is shown that the effects of the two downstream stator rows on the time-mean blade flow field are negligible, permitting its investigation using isolated rotor calculations. Simulations of this type are carried out along the engine operating line to quantify the acoustic sources associated with the upstream shock field and wake turbulence-stator interaction. The shock noise achieves its maximum value near the flyover acoustic certification condition, while the wake turbulence is least at this condition owing to its proximity to the design point. The behavior of these noise sources is explained physically by carrying out a detailed examination of the rotor flow field. The unsteady interaction between the rotor and stator rows at a high-power setting is investigated next. It is shown that the time-mean IGV flow is significantly affected by this interaction. Moreover, the unsteady loading on the IGV is found to be large. The behavior of the upstream-propagating acoustic field generated by rotor-IGV interaction is examined. The interaction between the rotor and FEGV is found to be linear in nature. The FEGV surface unsteady pressure and far-field acoustic field behavior are investigated.

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17

Pintér, Balázs. "Solar atmospheric magnetic effects on global acoustic and atmospheric gravity eigenoscillations." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364, no. 1839 (December 19, 2005): 541–45. http://dx.doi.org/10.1098/rsta.2005.1717.

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Solar global observations suggest that the frequency and the line width of helioseismic acoustic eigenmodes vary with the solar cycle. One reason for the measured changes could be the variation of the global atmospheric magnetic fields. We model global solar oscillations in a plane-parallel, three-layer model within the framework of linear dissipative magnetohydrodynamics, and study the effects of a homogenous, horizontal atmospheric magnetic field on global oscillations. We find magnetoacoustic f - and p -modes and also atmospheric gravity modes ( g -modes) among the eigenoscillations of the system. We conclude that changes in the atmospheric magnetic field can, significantly, shift the frequencies and vary the line width of global oscillation modes.

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Kuo, Ching-Wen, Jérémy Veltin, and Dennis K. McLaughlin. "Effects of Jet Noise Source Distribution on Acoustic Far-Field Measurements." International Journal of Aeroacoustics 11, no. 7-8 (December 2012): 885–915. http://dx.doi.org/10.1260/1475-472x.11.7-8.885.

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Zhou, Yufeng. "The Effects of Phase-Modulated Excitation on the Focused Acoustic Field." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 67, no. 4 (April 2020): 727–34. http://dx.doi.org/10.1109/tuffc.2019.2955453.

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Bakhtiari-Nejad, Marjan, and Shima Shahab. "Effects of Nonlinear Propagation of Focused Ultrasound on the Stable Cavitation of a Single Bubble." Acoustics 1, no. 1 (December 6, 2018): 14–34. http://dx.doi.org/10.3390/acoustics1010003.

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Many biomedical applications such as ultrasonic targeted drug delivery, gene therapy, and molecular imaging entail the problems of manipulating microbubbles by means of a high-intensity focused ultrasound (HIFU) pressure field; namely stable cavitation. In high-intensity acoustic field, bubbles demonstrate translational instability, the well-known erratic dancing motion, which is caused by shape oscillations of the bubbles that are excited by their volume oscillations. The literature of bubble dynamics in the HIFU field is mainly centered on experiments, lacking a systematic study to determine the threshold for shape oscillations and translational motion. In this work, we extend the existing multiphysics mathematical modeling platform on bubble dynamics for taking account of (1) the liquid compressibility which allows us to apply a high-intensity acoustic field; (2) the mutual interactions of volume pulsation, shape modes, and translational motion; as well as (3) the effects of nonlinearity, diffraction, and absorption of HIFU to incorporate the acoustic nonlinearity due to wave kinematics or medium—all in one model. The effects of acoustic nonlinearity on the radial pulsations, axisymmetric modes of shape oscillations, and translational motion of a bubble, subjected to resonance and off-resonance excitation and various acoustic pressure, are examined. The results reveal the importance of considering all the involved harmonics and wave distortion in the bubble dynamics, to accurately predict the oscillations, translational trajectories, and the threshold for inertial (unstable) cavitation. This result is of interest for understanding the bubble dynamical behaviors observed experimentally in the HIFU field.

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RODRÍGUEZ, O. C., S. JESUS, Y. STEPHAN, X. DEMOULIN, M. PORTER, and E. COELHO. "NONLINEAR SOLITON INTERACTION WITH ACOUSTIC SIGNALS: FOCUSING EFFECTS." Journal of Computational Acoustics 08, no. 02 (June 2000): 347–63. http://dx.doi.org/10.1142/s0218396x0000025x.

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The problem of nonlinear interaction of solitary wave packets with acoustic signals has been intensively studied in recent years. A key goal is to explain the observed transmission loss of shallow-water propagating signals, which has been found to be strongly time-dependent, anisotropic, and sometimes exhibited unexpected attenuation versus frequency. Much of the existing literature considers the problem of signal attenuation in a static environment, without considering additional effects arising from groups of solitons evolving both in range and time. Hydrographic and acoustic data from the INTIMATE'96 experiment clearly exhibit the effects of soliton packets. However, in contrast with reported observations of signal attenuation, the observed transmission loss shows a pronounced signal enhancement that behaves like a focusing effect. This focusing is correlated with peaks in current, temperature, and surface tide. That correlation suggests that the nonlinear interaction of solitary wave packets with acoustic signals can lead to a focusing of the signal. To clarify this issue, hydrographic data was used to generate physically consistent distributions of "soliton-like" fields of temperature and sound velocity. These distributions were then used as input for a range-dependent normal-mode model. The results strongly support the hypothesis that the soliton field causes the observed signal enhancement.

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YANG, YANJU, CHUNLEI CHENG, WENYAO YANG, JIE LI, ZHENGFU CHENG, and XIAOYU ZHANG. "STUDY OF ACOUSTIC SOURCE EXCITED BY PULSED MAGNETIC FIELD." Journal of Mechanics in Medicine and Biology 21, no. 05 (April 14, 2021): 2140008. http://dx.doi.org/10.1142/s021951942140008x.

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In magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging, tissues are exposed to an alternating field, generating magnetoacoustic and thermoacoustic effects in the tissues. This study aimed to investigate the relationship between magnetoacoustic and thermoacoustic effects in a low-conductivity object put in a Gauss-pulsed alternating magnetic field. First, the derivations of the magnetic flux density and electric field strength induced by a Gauss-pulsed current flowing through the coil based on the theory of electromagnetic field were examined. Second, the analytical solution of the magnetic field was studied by simulation. To validate the accuracy of the analytical solution, the analytical solution and the numerical simulation of the magnetic flux density were compared. It shows that the analytical solution coincides with the numerical simulation well. Then, based on the theoretical analysis of the acoustic source generation, numerical studies were conducted to simulate pressures excited by magnetoacoustic and thermoacoustic effects in low-conductivity objects similar to tissues in the Gauss-pulsed magnetic field. The thermoacoustic effect played a leading role in low-conductivity objects placed in the Gauss-pulsed magnetic field, and the magnetoacoustic effect could be ignored. This study provided the theoretical basis for further research on magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging for pathological tissues.

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Ambrose, Skip, Christine Florian, Justin Olnes, John MacDonald, and Therese Hartman. "Sagebrush Soundscapes and the Effects of Gas-Field Sounds on Greater Sage-Grouse." Western Birds 52, no. 1 (February 1, 2021): 23–46. http://dx.doi.org/10.21199/wb52.1.2.

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Greater Sage-Grouse (Centrocercus urophasianus) use elaborate acoustic and visual displays to attract and select mates, and females and chicks depend on acoustic communication during brood rearing. A potential threat to the grouse is sounds associated with human activity. During April, 2013–2020, we collected 17,825 hours of acoustic data in three different acoustic situations in the sagebrush of Wyoming: rural, undeveloped areas (6), at Greater Sage-Grouse leks in a natural-gas field (20), and near active machinery in that gas field (17). The average existing sound levels in undeveloped sagebrush areas were LAeq = 26 dB and LA50 = 20 dB, and the average background sound level was LA90 = 14 dB. These values are lower than previously reported, due in part to our use of more sensitive equipment as well as addressing the influence of the instruments’ electronic self-noise. LAeq and LA50 at leks in the gas field ranged from 25.5 to 33.7 dB and 20.5 to 31.3 dB, respectively, depending on the distance, number, and type of nearby activities. Sound levels at leks were correlated with trends in the number of grouse using the lek: the higher the sound level, the greater the likelihood of a decline. Thresholds above which declines occurred were LAeq = 31 dB and LA50 = 26 dB. Leks with LAeq > 31 dB and LA50 >26 dB, 100% and 91%, respectively, had declining trends. Our findings suggest that the current policy of limiting sound levels at leks to LA50 < 10 dB (or LAeq < 15 dB) over the background sound level is appropriate, if an accurate background level is used.

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Qian, Zhiwen, Dejiang Shang, Yuan Hu, Xinyang Xu, Haihan Zhao, and Jingsheng Zhai. "A Green’s Function for Acoustic Problems in Pekeris Waveguide Using a Rigorous Image Source Method." Applied Sciences 11, no. 6 (March 18, 2021): 2722. http://dx.doi.org/10.3390/app11062722.

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The Green’s function (GF) directly eases the efficient computation for acoustic radiation problems in shallow water with the use of the Helmholtz integral equation. The difficulty in solving the GF in shallow water lies in the need to consider the boundary effects. In this paper, a rigorous theoretical model of interactions between the spherical wave and the liquid boundary is established by Fourier transform. The accurate and adaptive GF for the acoustic problems in the Pekeris waveguide with lossy seabed is derived, which is based on the image source method (ISM) and wave acoustics. First, the spherical wave is decomposed into plane waves in different incident angles. Second, each plane wave is multiplied by the corresponding reflection coefficient to obtain the reflected sound field, and the field is superposed to obtain the reflected sound field of the spherical wave. Then, the sound field of all image sources and the physical source are summed to obtain the GF in the Pekeris waveguide. The results computed by this method are compared with the standard wavenumber integration method, which verifies the accuracy of the GF for the near- and far-field acoustic problems. The influence of seabed attenuation on modal interference patterns is analyzed.

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Cui, Huaifeng, Rufu Hu, and Nan Chen. "Modelling and analysis of acoustic field in a rectangular enclosure bounded by elastic plates under the excitation of different point force." Journal of Low Frequency Noise, Vibration and Active Control 36, no. 1 (March 2017): 43–55. http://dx.doi.org/10.1177/0263092317693488.

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The coupled acoustic field of fully elastic plate model is described by the modal analysis method. The acoustic potential energy resonance peaks of the fully elastic plate model are significantly more than that of the one elastic plate model due to the influence of the vibration of multi elastic plates. The acoustic field characteristics of the fully elastic plate model are analyzed when the primary excitation source is applied on the different elastic plates. The results show that the coupled acoustic field of the fully elastic plate model is dominated by the structural mode of the elastic plate with primary excitation, and the acoustic mode of the enclosure, and the structural-acoustic coupling between the plate and the enclosure; the structure modes of the other elastic plates have less effects on the acoustic field in the enclosure except the first ones of them.

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Li, Li, Ning Gu, Huijuan Dong, Bingsheng Li, and Kenneth T. V. G. "Analysis of the effects of acoustic levitation to simulate the microgravity environment on the development of early zebrafish embryos." RSC Advances 10, no. 72 (2020): 44593–600. http://dx.doi.org/10.1039/d0ra07344j.

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Luo, Y., and L. F. Chernogor. "ELECTROMAGNETIC EFFECTS OF ACOUSTIC AND ATMOSPHERIC GRAVITY WAVES IN THE NEAR-EARTH ATMOSPHERE." Radio physics and radio astronomy 25, no. 4 (December 2, 2020): 290–307. http://dx.doi.org/10.15407/rpra25.04.290.

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Purpose: Acoustic and atmospheric gravity waves (AAGW) are generated by many natural and anthropogenic sources. The AAGW propagation at ionospheric heights is accompanied by the generation of disturbances in the magnetic and electric fields. The plasma presence plays a crucial role. The mechanisms for generating electrical and magnetic disturbances in the near-Earth atmosphere by the AAGW have been studied much worse. Therefore, the validation of the capability to generate electromagnetic disturbances in the near-Earth atmosphere by the AAGW is an urgent problem. The purpose of this paper is to describe the mechanism for generating disturbances in the electric and magnetic fields in the near-Earth atmosphere under the action of AAGW and to estimate the amplitudes of these disturbances for various AAGW sources. Design/methodology/approach: The impact of a series of highenergy sources often results in the generation of synchronous disturbances in the acoustic and geoelectric (atmospheric) fields, when an approximate proportionality between the pressure amplitude and the amplitude of the disturbances in the atmospheric electric field is observed to occur. Based on the observational data and making use of the Maxwell equations, the theoretical estimates of the disturbances in the electric and magnetic fields have been obtained. Findings: Simplified expressions have been obtained for estimating the amplitudes of the electric and magnetic fields under the action of the AAGW generated by natural and manmade sources. The amplitudes of the electric and magnetic fields generated by the AAGW of natural and manmade origin, which travel in the near-Earth atmosphere, have been calculated. The amplitudes of the AAGW generated electric and magnetic fields are shown to be large enough to be detected with the existing electrometers and fluxmeter magnetometers. The magnitudes of the amplitudes of the electric and magnetic fields generated in the near-Earth atmosphere under the action of AAGW are large enough to trigger coupling between the subsystems in the Earth–atmosphere–ionosphere–magnetosphere system. Conclusions: The estimates and not numerous observations are in good agreement. Key words: acoustic and atmospheric gravity waves, near-Earth atmosphere, volume charge, atmospheric pressure disturbances, electric field, magnetic field

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CHIU, YUNG-SHENG, YUAN-YING CHANG, LI-WEN HSIEH, MEI-CHUN YUAN, and CHI-FANG CHEN. "THREE-DIMENSIONAL ACOUSTICS EFFECTS IN THE ASIAEX SCS EXPERIMENT." Journal of Computational Acoustics 17, no. 01 (March 2009): 11–27. http://dx.doi.org/10.1142/s0218396x09003835.

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A three-dimensional (3D) ocean environment is assimilated with measured ocean data in the ASIAEX SCS (Asian Seas International Acoustics EXperiment, South China Sea) experiment. The experiment site is characterized as an active internal wave propagation region along the Northwestern shelf break of the South China Sea. Three-dimensional acoustics effects in the area are studied using FOR3DW, a wide-angle version of the parabolic equation code FOR3D (a Finite difference solution, an Ordinary differential equation, and Rational function approximations for solving 3D problems), and MOS3DPEF (MOdal Spectrum analysis based on 3D PE Field). The TL comparison between Nx2D and 3D calculations are shown to demonstrate the 3D effects. Variations in topography of the shelf break and in the water column due to the internal waves cause the 3D effects in the acoustic field. The intercomparison of the importance of bottom steering 3D effects and nonlinear internal wave refraction 3D effects is therefore proposed to realize which possesses the major part of the 3D effects. Also, 3D modal analysis results show that the nonlinear internal wave front causes severe horizontal refraction for higher modes.

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Zong, Ning, Guang Jun Yang, and Jing Sun. "Effects of Roughness Strip and Acoustic Sensor Height on Subsonic Boundary Layer by Experiment." Applied Mechanics and Materials 421 (September 2013): 459–63. http://dx.doi.org/10.4028/www.scientific.net/amm.421.459.

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According to the measurement requirements of acoustic fatigue load on aft fuselage structure and the external installation restriction of the acoustic sensor on aircraft surface, an acoustic sensor is installed on the silencing jet test plate with reference to body type of the real aircraft. A dynamic test and analysis system combined hot wire wind speed measurement and acoustic spectrum measurement is built up for the combined experiments with different acoustic sensor height and various boundary layer flow structure at subsonic flow condition. Turbulence development of different boundary layer is analyzed. The test result can be coordinated with the local measurement to aircraft flow structure so as to estimate the effect of acoustic sensor on the flow field.

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Achury, Javier, and Wolfgang Polifke. "Modulation of spray droplet number density and size distribution by an acoustic field." Journal of Computational Multiphase Flows 9, no. 1 (February 12, 2017): 32–46. http://dx.doi.org/10.1177/1757482x17690751.

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Multiple interactions may occur when a poly-disperse spray is exposed to an acoustic field. In the context of spray combustion instabilities, acoustic agglomeration, the formation of a droplet number density wave and the modulation of the droplet size distribution are interesting effects. A droplet number density wave, i.e. preferential concentration of droplets in space, may result from size-dependent, one-way momentum coupling between the acoustic field and the spray. The modulation of the droplet size distribution, which has been evidenced in the experimental work of Gurubaran and Sujith (AIAA 2008-1046), is thus a consequence of the droplet number density wave formation. In the present work, the mechanisms that produce these effects are simulated and analyzed in depth by means of computational fluid dynamics. The spray is modeled with both Lagrangian (particles mass-point approach) and Eulerian (continuous phase approach) descriptions. The particular Eulerian method used is a variant of the presumed density function method of moments, which allows to account for the effects of poly-dispersity, in particular the size-dependence of particle velocity. Both the Lagrangian and Eulerian models are validated against experimental data for spray dynamics and spray response to an acoustic field.

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Zhang, Dongxu, Chunxiao Kong, Mei Zhang, and Qi Meng. "Courtyard Sound Field Characteristics by Bell Sounds in Han Chinese Buddhist Temples." Applied Sciences 10, no. 4 (February 14, 2020): 1279. http://dx.doi.org/10.3390/app10041279.

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The acoustic environments of Han Chinese Buddhist temples have long played an important role in the development of Buddhism. This study explored the effects of layouts and spatial elements of Han Chinese Buddhist temples on courtyard sound fields. First, sound fields of three traditional Han Chinese courtyards were measured, and results were compared with sound field simulations to determine the appropriate acoustic and software parameter setting for ancient building materials in the context of sound field simulation. Next, a sound field model for standard forms of Han Chinese Buddhist temples was built and analysed. Results indicate that in traditional Buddhist temples, spatial elements—such as the height and sound absorption coefficient of temple courtyard walls, position of courtyard partition walls, and the position and height of bell towers—could significantly affect the sound pressure level (SPL), reverberation time (RT), and musical clarity (C80) of each courtyard. However, enclosure materials, such as those used in roofs, on the ground, and in windows of Han Chinese Buddhist temples, had relatively small effects on temple courtyard sound fields.

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Strasser, Helmut, Kristina Gruen, and Werner Koch. "Office acoustics: Analyzing reverberation time and subjective evaluation." Occupational Ergonomics 2, no. 2 (December 1, 1999): 67–80. http://dx.doi.org/10.3233/oer-2000-2201.

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Members of the design department in a medium-sized company were complaining to the management about the acoustic situation in new offices which adversely affected their personal well-being and their work performance. Therefore, a field study was conducted to analyze and evaluate the acoustic working conditions in the new offices and to develop improvements where necessary. Objective criteria for the evaluation of communication disturbances during meetings or telephone conversations were obtained by measuring the reverberation time in several offices. Questionnaires with unipolar or bipolar 4-step scales allowed a differentiated judgement of the current acoustic situation and its effects on the person or individual. Improvements of the acoustics were developed and cost-utility prognoses were made. The proposed solutions and their prospective acceptance rate among the employees were assessed before they were implemented.

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Kerechanin, C. W., M. Samimy, and J. H. Kim. "Effects of Nozzle Trailing Edges on Acoustic Field of Supersonic Rectangular Jet." AIAA Journal 39, no. 6 (June 2001): 1065–70. http://dx.doi.org/10.2514/2.1418.

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Koyama, Daisuke, Nicolas Barbier, and Yoshiaki Watanabe. "Shell Effects on Vibration Behavior of a Microcapsule in an Acoustic Field." Japanese Journal of Applied Physics 42, Part 1, No. 10 (October 9, 2003): 6700–6704. http://dx.doi.org/10.1143/jjap.42.6700.

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Bulanov, A. V., and E. V. Sosedko. "Opto-Acoustic Effects by Laser Breakdown of Seawater in an Ultrasonic Field." Doklady Earth Sciences 491, no. 1 (March 2020): 183–86. http://dx.doi.org/10.1134/s1028334x20030022.

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Kerechanin, C. W. II, M. Samimy, and J. H. Kim. "Effects of nozzle trailing edges on acoustic field of supersonic rectangular jet." AIAA Journal 39 (January 2001): 1065–70. http://dx.doi.org/10.2514/3.14840.

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Cochrane, Norman A., and Gary D. Melvin. "Acoustic near field effects for the Simrad–Mesotech SM 2000 multibeam sonar." Journal of the Acoustical Society of America 114, no. 4 (October 2003): 2307. http://dx.doi.org/10.1121/1.4809240.

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Zhu, Haodong, Peiran Zhang, Zhanwei Zhong, Jianping Xia, Joseph Rich, John Mai, Xingyu Su, et al. "Acoustohydrodynamic tweezers via spatial arrangement of streaming vortices." Science Advances 7, no. 2 (January 2021): eabc7885. http://dx.doi.org/10.1126/sciadv.abc7885.

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Acoustics-based tweezers provide a unique toolset for contactless, label-free, and precise manipulation of bioparticles and bioanalytes. Most acoustic tweezers rely on acoustic radiation forces; however, the accompanying acoustic streaming often generates unpredictable effects due to its nonlinear nature and high sensitivity to the three-dimensional boundary conditions. Here, we demonstrate acoustohydrodynamic tweezers, which generate stable, symmetric pairs of vortices to create hydrodynamic traps for object manipulation. These stable vortices enable predictable control of a flow field, which translates into controlled motion of droplets or particles on the operating surface. We built a programmable droplet-handling platform to demonstrate the basic functions of planar-omnidirectional droplet transport, merging droplets, and in situ mixing via a sequential cascade of biochemical reactions. Our acoustohydrodynamic tweezers enables improved control of acoustic streaming and demonstrates a previously unidentified method for contact-free manipulation of bioanalytes and digitalized liquid handling based on a compact and scalable functional unit.

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Lin, Yi-Wei, and Gee-Pinn James Too. "A Parametric Study of Sound Focusing in Shallow Water by Using Acoustic Contrast Control." Journal of Computational Acoustics 22, no. 04 (September 18, 2014): 1450012. http://dx.doi.org/10.1142/s0218396x1450012x.

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Acoustic contrast control is a sound focusing technique applied to personal audio system devices to provide the optimal sound contrast for increasing or decreasing the potential sound energy of a specific area. In this study, acoustic contrast control was developed for sound focusing in shallow water. The advantage of this technique is the establishment of two zones: a bright zone around the user and a dark zone for other regions. In the acoustic contrast control process, computational ocean acoustics are used to calculate the Green's function between the source point and the field point. The effects of environmental parameters, which comprised the number of control sources, transmission frequency, control distances between sources and control zone of a geometric location were simulated. The results show that acoustic contrast control is an effective approach for sound focusing in shallow water that can increase the potential sound energy of a specific area. Employing this technique can also enhance underwater communications by using frequency-shift keying modulation for cross-talking applications.

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PORTER, MICHAEL B., MATT TATTERSALL, and J. P. IANNIELLO. "ASSESSMENT OF 3-D EFFECTS IN THE KEY WEST LWAD EXPERIMENT." Journal of Computational Acoustics 09, no. 02 (June 2001): 347–58. http://dx.doi.org/10.1142/s0218396x01001066.

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The role of 3-D effects has long been debated in the ocean acoustics community. Typically, 3-D problems are handled in an approximation that uses a fan of bearing lines to build up a 3-D image of the acoustic field with many 2-D slices. This is the so-called N by 2-D approach and it is probably safe to say it is adequate for simple calculations of the SONAR range-of-the-day. On the other hand, acoustic models are now finding an important role in matched-field processing (MFP) where they are integrated with the signal processing to correct for the channel effects. These applications demand much more from the models but, somewhat surprisingly, recent broadband experiments have revealed that the models are up to the task. The main features of the echo patterns are well-predicted by such models and can be reliably exploited, at least in areas where the ocean bottom is fairly flat. The challenge now is to push MFP to more realistic scenarios with complicated topography and potential 3-D effects. One phase of the December 1997 Key West LWAD (Littoral Warfare Advance Development) experiment was designed to address exactly this issue. We use this Key West scenario as a backdrop to discuss modeling approaches combining beams and modes and the impact of the resulting 3-D variation on MFP for towed arrays.

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Liu, Jinpeng, Zheng Zhu, Yongqiang Ji, Ziyang Chen, Chao Zhang, and Dejiang Shang. "Prediction of Sound Scattering from Deep-Sea Targets Based on Equivalence of Directional Point Sources." Applied Sciences 11, no. 11 (June 2, 2021): 5160. http://dx.doi.org/10.3390/app11115160.

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A fast prediction method is proposed for calculating the sound scattering of targets in the deep-sea acoustic channel by equating the sound scattering field of a complex elastic target to the acoustic field excited by a directional point source. In deep-sea conditions, the effects of the sea surface on the impedance characteristics of the elastic target surface can be ignored. Through the finite element simulation of the acoustic scattering of the target in the free field, the sound scattering field is equated to the radiation field of a directional point source. Subsequently, the point source is placed in the channel, and the acoustic ray method is used to calculate the distribution of the scattering field. On the basis of theoretical modelling, the method of obtaining the directional point source and the influence of the sea surface on the impedance of the scattering field are analysed. Subsequently, the proposed method is compared with the finite element method in terms of computational efficiency. The result shows that the method considers the multiple complex coupling effects between the elastic structure and marine environment. The influence of the boundary is approximately negligible when the distance from the ocean boundary to the elastic structure is equal to the wavelength. The method only performs finite element coupling calculation in the free field; the amount of mesh size is greatly reduced and the calculation efficiency is significantly improved when compared with the finite element calculation in the entire channel, the. The calculation time in the example can be reduced by more than one order of magnitude. This method organically combines the near-field calculation with acoustic ray theory and it can realise the rapid calculation of the large-scale acoustic scattering field in complex marine environments.

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Bigot, Lionel. "Theory of Magneto-Acoustic Modes in roAp Stars." International Astronomical Union Colloquium 193 (2004): 445–52. http://dx.doi.org/10.1017/s0252921100011118.

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AbstractIn this review I present the effects of a strong magnetic field on the pulsations of rapidly oscillating Ap stars. I show how the field affects the observables, such as the frequencies and eigenvectors, and the selection of modes.

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Bailey, Nathan W., and Marlene Zuk. "Acoustic experience shapes female mate choice in field crickets." Proceedings of the Royal Society B: Biological Sciences 275, no. 1651 (August 12, 2008): 2645–50. http://dx.doi.org/10.1098/rspb.2008.0859.

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Female choice can drive the evolution of extravagant male traits. In invertebrates, the influence of prior social experience on female choice has only recently been considered. To better understand the evolutionary implications of experience-mediated plasticity in female choice, we investigated the effect of acoustic experience during rearing on female responsiveness to male song in the field cricket Teleogryllus oceanicus . Acoustic experience has unique biological relevance in this species: a morphological mutation has rendered over 90 per cent of males on the Hawaiian island of Kauai silent in fewer than 20 generations, impeding females' abilities to locate potential mates. Females reared in silent conditions mimicking Kauai were less discriminating of male calling song and more responsive to playbacks, compared with females that experienced song during rearing. Our results to our knowledge, are the first demonstration of long-term effects of acoustic experience in an arthropod, and suggest that female T. oceanicus may be able to compensate for the reduced availability of long-range male sexual signals by increasing their responsiveness to the few remaining signallers. Understanding the adaptive significance of experience-mediated plasticity in female choice provides insight into processes that facilitate rapid evolutionary change and shape sexual selection pressure in natural populations.

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Fadeev, G. N., V. S. Boldyrev, N. A. Bogatov, and A. L. Nikolaev. "Inhibition of oxidated reducing reactions in the field of low frequency impacts." Доклады Академии наук 487, no. 3 (August 17, 2019): 275–78. http://dx.doi.org/10.31857/s0869-56524873275-278.

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The effect of low-frequency oscillations on a system consisting of two biochemically active components: the dye of methylene blue and ascorbic acid is investigated. Each of these components can be reversibly oxidized and reduced. The system is interesting in that it makes it possible to trace the influence of the low-frequency acoustic field on the mutual redox process and to reveal the features of the effect of such oscillations. It was found that, in this system, with the introduction of low-frequency effects, redox processes are not accelerated, but slowed down. There is an effect inhibition of the sound-chemical process in the field of low-frequency acoustic effects. The effect is quantified.

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Ayton, Lorna J. "Acoustic scattering by a finite rigid plate with a poroelastic extension." Journal of Fluid Mechanics 791 (February 24, 2016): 414–38. http://dx.doi.org/10.1017/jfm.2016.59.

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The scattering of sound by a finite rigid plate with a finite poroelastic extension interacting with an unsteady acoustic source is investigated to determine the effects of porosity, elasticity and the length of the extension when compared to a purely rigid plate. The problem is solved using the Wiener–Hopf technique, and an approximate Wiener–Hopf factorisation process is implemented to yield reliable far-field results quickly. Importantly, finite chord-length effects are taken into account, principally the interaction of a rigid leading-edge acoustic field with a poroelastic trailing-edge acoustic field. The model presented discusses how the poroelastic trailing-edge property of owls’ wings could inspire quieter aeroacoustic designs in bladed systems such as wind turbines, and provides a framework for analysing the potential noise reduction of these designs.

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Chen, Tzeng-Yuan, and Man-Ge Chen. "Investigations of Thermo-Acoustic Instabilities by Direct Acoustic Admittance Measurements." Journal of Mechanics 16, no. 3 (September 2000): 133–36. http://dx.doi.org/10.1017/s1727719100001787.

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ABSTRACTThis research applied the method of direct acoustic admittance measurement to investigate effects of the flame character and the burner acoustic admittance on the flame-driving behavior. The acoustic admittance data were obtained by directly measuring the amplitudes of pressure and velocity oscillations, and the phase relations between the pressure and velocity oscillations. Results of this research reveal that the flame-driving characteristic is mainly dominated by the nonreactive burner admittance not the flame. Whether the flame is to drive or damp the acoustic field is detcrmined by the acoustic admittance of the burner system. The flame equivalence ratio plays a role mainly in determining the magnitude of the flame driving/damping.

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Yavuzkurt, S., M. Y. Ha, G. Reethof, G. Koopmann, and A. W. Scaroni. "Effect of an Acoustic Field on the Combustion of Coal Particles in a Flat Flame Burner." Journal of Energy Resources Technology 113, no. 4 (December 1, 1991): 286–93. http://dx.doi.org/10.1115/1.2905913.

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The effects of an acoustic field on the enhancement of coal combustion are investigated. A flat flame burner using methane-air mixtures as the fuel is used for the experiments. Micronized coal particles 20–70 μm in diameter are injected into the burning gas stream at the same velocity as the gas. The light intensity emitted from the flame, temperature and pictures of the flame with and without an acoustic field are recorded. The nominal values of the intensity of the acoustic field are between 140–160 dB and the frequency is between 500–3500 Hz. A definite increase in the rate of combustion of the coal particles is observed with the application of an acoustic field. The enhancement can be seen from the increased light intensity of the flame and the flame width. This paper presents the data and a discussion of light intensity emitted by the flame as a function of acoustic parameters.

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Altay, Rana, Abdolali K. Sadaghiani, M. Ilker Sevgen, Alper Şişman, and Ali Koşar. "Numerical and Experimental Studies on the Effect of Surface Roughness and Ultrasonic Frequency on Bubble Dynamics in Acoustic Cavitation." Energies 13, no. 5 (March 3, 2020): 1126. http://dx.doi.org/10.3390/en13051126.

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With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.

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STOKER, ROBERT W., and MARILYN J. SMITH. "AN EVALUATION OF FINITE VOLUME DIRECT SIMULATION AND PERTURBATION METHODS IN CAA APPLICATIONS." Journal of Computational Acoustics 03, no. 04 (December 1995): 281–95. http://dx.doi.org/10.1142/s0218396x95000148.

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A number of questions have emerged in the field of Computational Aeroacoustics (CAA) over the capability of applying conventional Computational Fluid Dynamics (CFD) methodologies to capture the physical attributes of acoustic fields. One of the more fundamental questions is the capability of direct simulation techniques versus perturbation techniques to capture the acoustic phenomena. This issue is the topic of this research; wherein one such methodology, an explicit four stage Runge–Kutta finite volume scheme, has been utilized for acoustic simulations using both direct simulation and perturbation approaches. The two-dimensional unsteady Euler equations are solved directly for the direct simulation methodology, while in the perturbation method the steady mean flow Euler equations are subtracted from the fully unsteady Euler equations, and the remaining perturbed equations are then solved for the acoustic flow quantities. These methodologies have been compared by applying them to a standard acoustic problem, the acoustic field of a point monopole. Emphasis has been placed on the ability of the methodology to capture the physics of the problem. The effects of dissipation, grid spacing, and amplitude have been addressed and compared for both methodologies. While both methods gave comparable results for most of the cases, the direct simulation methodology was found to have difficulties resolving small amplitude acoustic waves.

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MAMUN, A. A., and M. H. A. HASSAN. "Effects of dust grain charge fluctuation on an obliquely propagating dust acoustic solitary potential in a magnetized dusty plasma." Journal of Plasma Physics 63, no. 2 (February 2000): 191–200. http://dx.doi.org/10.1017/s0022377899008028.

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Effects of dust grain charge fluctuation, obliqueness and external magnetic field on a finite-amplitude dust acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge-fluctuating dust grains, are investigated using the reductive perturbation method. It is shown that such a magnetized dusty plasma system may support a dust acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self- consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust acoustic solitary potential significantly. The implications of these results for some space and astrophysical dusty plasma systems, especially planetary ring systems and cometary tails, are briefly mentioned.

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Journal articles on the topic 'Acoustic field effects'

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