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I.IntroductionUndcrwatersoundrevcrberationhasrccentlybecomeatopicofgreatinterestlI-3l.Sincethcrcverberationincludescombincdeffcctsofsoundpropagahonandscattering,andthesoundpropagationinshallowwaterismuchmorecomplicatedthanthatinthedeepsea,itisnecessarytOstudycarefullybothintheoryandexperimcnt.Fortheshortrangereverberationinshal1owwatcrtheray-basedmodelisavai1ab1e,whilefOr1ongrangethewave-basedmodelmustbeusedbecauscofcomp1icatcdmu1tipaths,refractioneffcctsandfrequencydependence.Thenorma1-mode… 相似文献
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利用传播损失反演海底单参数 总被引:2,自引:0,他引:2
根据地声反演复杂性随着待反演参数的个数减少不断降低的原理,提出一种利用传播损失反演海底单个参数的方法。通过对海底声阻抗的推导,利用声速、密度和衰减系数拟合出海底反射损失对掠射角的斜率F。基于简正波理论推导了用F描述声场的公式,并据此设计出对传播损失数据进行最小二乘法处理的反演方法。得益于将待反演参数减少至一个,该方法只需单个水听器,避免了复杂测量及多维寻优。对东海实验数据进行了实际反演,并介绍了利用反演结果F进行传播损失预报和海底性质估计的步骤。所获结果与多参数混合反演方法及实测真值进行比较,其一致性验证了方法的有效性。 相似文献
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A. V. Grinyuk V. N. Kravchenko A. T. Trofimov O. I. Trusova M. M. Tikhomirov A. A. Khil’ko A. I. Malekhanov V. V. Kovalenko A. I. Khil’ko 《Acoustical Physics》2011,57(5):661-666
Possibilities of high-frequency acoustical underwater observations of small-size objects in marine shelf zones are experimentally
investigated using vertical and horizontal arrays radiating and receiving complex structure pulses in the presence of strong
reverberation. Reconstruction of parameters of the observed objects yielded 35- to 40-dB weakening of the reverberation interferences
due to medium-matched spatial, temporal, and Doppler filtering. 相似文献
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浅海混响的垂直相干性 总被引:7,自引:6,他引:1
浅海混响垂直相干特性是海洋混响研究中一个重要的课题。在射线简正波混响理论的基础上,给出了浅海混响垂直相关的一般表达式,并推导出了在均匀层浅海中混响垂直相关的简化解析表达式。同时,通过对数值计算及实验结果的讨论,研究了浅海混响垂直相关与混响时间、频率、声源深度、接收器深度、海底衰减特性及海底散射系数等参数的变化关系。研究表明,在海底散射满足可分离性的条件下,浅海海底混响的垂直相关与声源位置无关,随着混响时间和海底衰减的增加、或随频率、接收器间隔和海深的减小,混响的垂直相关增大。 相似文献
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为了获得空气中远距离声源激发水下声场的精细结构,2013年3月,声场声信息国家重点实验室在南海海域进行了一次空气中声源激发水下声场的实验。采用汽笛作为空气声源,海底放置水听器作为接收,在实验过程中,发射船由距离水听器2.4 km处行驶至9.8 km。本文对该次实验数据进行分析,获得了收发距离远达9.8 km、频率分别为128 Hz和256 Hz的声传播损失曲线,该曲线随传播距离变化存在清晰的震荡结构.利用波数积分方法计算实验环境下的水下声场理论值,并对获得的声场传播特性进行了较好的物理解释。 相似文献
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《声学学报:英文版》2017,(2)
The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics. 相似文献
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Using numerical simulation, an analysis was conducted of the interference structure of a bottomscattered sound field generated by a wideband point source in shallow water under winter and summer conditions. The scattered signals were received from the place where the source was located and were subjected to Fourier transform with a sliding window. The paper demonstrates the possibility of estimating the waveguide invariant for backscattered signals when processing the sound intensity distributions in wide frequency and distance ranges up to the scattering area. A technique is proposed for reconstructing the twodimensional field of internal waves using variations of the interference pattern of reverberation signals. The influence of wind surface waves on the degree of interference band contrast is illustrated. 相似文献
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《Journal of sound and vibration》1987,119(2):215-223
In this paper, the general expressions of long-range reverberation intensity in shallow water have been developed on the basis of the normal mode theory. Because the effects of the complex eigenvalues on the mode incident field have been considered, the results are more accurate than those in previous former normal mode theories of reverberation. In addition, for the sake of simplifying the calculations and making the results convenient to compare with experiments, the reverberation intensity has been smoothed by space averaging. The expressions obtained have obvious physical meaning and concise form so that they can be used for numerical calculation and analytical discussion. These expressions are suitable for wider types of velocity profile, bottom-reflection and scattering coefficients. As an example, the average reverberation intensity in shallow water with a thermocline is evaluated. The result shows that when both the source and receiver are located above the thermocline, the long-range reverberation intensity is proportional to r−5. This result is in agreement with the experimental data. 相似文献
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浅海平均混响强度的数值模拟 总被引:1,自引:0,他引:1
海中混响是回声探测的严重干扰。利用本文给出的混响模型可较快地计算分层海洋中平均混响强度的衰减规律及深度结构。
对于近程混响,由于海水非均匀性的影响较小,使用均匀层的射线方法计算。对于远程混响,使用简正波方法计算,它保持了平滑平均后的深度结构。在中等距离上两者能很好地衔接起来,由于考虑了复本征值对简正波入射场的影响,提高了计算精度,通过比较不同散射模型对混响强度计算的影响,提出以分离型二元散射模型作为混响数值模拟的基础,使能由界面反向散射系数估算二元后向散射系数,并大大简化混响强度的数值计算。 相似文献
对于近程混响,由于海水非均匀性的影响较小,使用均匀层的射线方法计算。对于远程混响,使用简正波方法计算,它保持了平滑平均后的深度结构。在中等距离上两者能很好地衔接起来,由于考虑了复本征值对简正波入射场的影响,提高了计算精度,通过比较不同散射模型对混响强度计算的影响,提出以分离型二元散射模型作为混响数值模拟的基础,使能由界面反向散射系数估算二元后向散射系数,并大大简化混响强度的数值计算。 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2010,(8)
The striations of the reverberation spectrum in the time-frequency distribution were observed in a shallow water acoustic experiment in 2002. A model following the coherent reverberation model developed in 2002 is presented to explain the observed striations. To examine the consistency between the measured data and numerical predictions, we have used a method based on Radon transform for determining the slope of the striations to the measured reverberation data and numerical predictions. The results indicate that the previously developed coherent reverberation model can predict the interference structure of the reverberation intensity in the time-frequency distribution. 相似文献
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Ainslie MA 《The Journal of the Acoustical Society of America》2007,121(6):3363-3376
Multipath ocean reverberation originating from the seabed in shallow isovelocity water, with particular attention to its information content in the cylindrical spreading and mode stripping regions, is considered. The reverberation is evaluated using Weston's flux integral method, both analytically with various simplifying approximations and numerically with all but one of these approximations rescinded. The functional form of the analytical solution is used to infer which physical seabed parameters can be extracted from measurements of reverberation. Coarse- and fine-grained sediments (sand and clay) are both considered. The main purpose of the numerical solutions is to check the accuracy of the analytical approximations; they also serve as a convenient surrogate for measured reverberation. 相似文献
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使用基于射线简正波异地混响理论建立的水平接收阵接收海底混响模型,提出了水平阵被动时反混响抑制方法。以水平接收阵接收回波信号的某一时刻作为开始,分别对其前一时刻和后一时刻的回波信号做时反算子分解获得两个混响子空间,将这两个混响子空间的平均作为该时刻的混响子空间的一个估计,然后利用投影处理来抑制该时刻接收信号中的混响成分。该方法可以在一定程度上克服由于海底粗糙引起的局部时间(距离)段内接收回波信号的不平稳性,使得估计得到的混响子空间更加接近真实混响子空间。因此,利用其进行被动时反混响抑制可以增强回波信混比,提高对目标的检测和方位估计能力。针对典型浅海波导环境开展的仿真验证了本文方法的有效性。 相似文献
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A numerical experiment is carried out to study the long-range surface reverberation in the presence of intense surface waves for the case of using vertical transmitting arrays providing sound field focusing at different depths. To focus the field, a phase conjugation of acoustic waves from a probe source positioned at the focusing point is used. It is demonstrated that surface waves considerably affect the focusing quality at a distance of several tens of kilometers from the transmitting array. This prevents the efficient suppression of long-range reverberation by increasing the focusing depth. 相似文献
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Mace BR Duhamel D Brennan MJ Hinke L 《The Journal of the Acoustical Society of America》2005,117(5):2835-2843
A method is presented by which the wavenumbers for a one-dimensional waveguide can be predicted from a finite element (FE) model. The method involves postprocessing a conventional, but low order, FE model, the mass and stiffness matrices of which are typically found using a conventional FE package. This is in contrast to the most popular previous waveguide/FE approach, sometimes termed the spectral finite element approach, which requires new spectral element matrices to be developed. In the approach described here, a section of the waveguide is modeled using conventional FE software and the dynamic stiffness matrix formed. A periodicity condition is applied, the wavenumbers following from the eigensolution of the resulting transfer matrix. The method is described, estimation of wavenumbers, energy, and group velocity discussed, and numerical examples presented. These concern wave propagation in a beam and a simply supported plate strip, for which analytical solutions exist, and the more complex case of a viscoelastic laminate, which involves postprocessing an ANSYS FE model. The method is seen to yield accurate results for the wavenumbers and group velocities of both propagating and evanescent waves. 相似文献
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M. Belhadi O. Rafil R. Tigrine A. Khater J. Hardy A. Virlouvet K. Maschke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):435-443
The influence of linear defect boundaries on the transmission and scattering of elastic waves in quasi-two-dimensional wave-guides
is studied using the matching method. A linear defect boundary separating two wave-guide crystalline lattice domains is characterised
here by a linear chain of defect masses and by modified elastic constants in the boundary, different from their values in
the bulk of the domains. In particular a square lattice is considered to model the domains of the two-dimensional planar wave-guide
containing the linear defect. The reflection and transmission probabilities, and the total transmission probabilities are
calculated numerically and presented for the scattering processes in a variety of cases. We show that the interaction between
the localised modes introduced by the defect boundary and the propagating modes of the system leads to Fano resonances. These
resonances shift to higher (lower) frequencies for smaller (larger) defect masses, and for the same mass as function of the
angle of the incident wave. Other spectral features shown to exist are due to interference effects especially at oblique incidence
and when modifying the boundary elastic constants.
Received 8 November 1999 and Received in final form 14 January 2000 相似文献
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处理并分析了2005黄海混响实验数据。在单层海底假设下利用300~800Hz频段混响垂直相关数据反演了海底参数,并分析了参数反演结果的不确定性。结果发现:单频独立反演的声速值随频率增加而减小。类似的结果以前也有报道,导致难以有效地确定海底的平均声速。为了解决这一问题,本文假设海底具有两层分层结构,并提出了一种基于遗传算法的多频联合海底参数反演方法。同一海域声传播数据的简正波分离结果以及混响垂直相干实验值与基于反演参数计算的理论值吻合良好,验证了分层海底假设及参数反演结果的有效性。 相似文献