共查询到20条相似文献,搜索用时 546 毫秒
1.
Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a bearing-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz–360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The bearing-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally,the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations. 相似文献
2.
3.
LI Qihu LI Shuqiu SUN Changyu YU Huabing 《声学学报:英文版》2007,26(3):193-197
The interference characteristics of towed platform noise resulted from propeller and towed body for active/passive towed array is analyzed. It is shown that, in shallow water environment, the direct wave and bottom/sea surface reflected wave will seriously affect the performance of sonar system. The formula for calculating the direction of arrival (DOA) of interference in terms of various parameters, such as array depth, length of tow cable, is derived. The effect of interference noise for the detection performance of sonar system is described. The results of system simulation provide the method for reducing the effect of these kind of interferences. 相似文献
4.
5.
6.
本文介绍近30年来水声信号处理领域理论研究的新进展和在声纳设计中的应用。包括水声信号建模、声场匹配、海洋波导和内波现象的探索和研究、声矢量场信息获取和处理,低频水声信道的时/空相关特性,水下目标辐射噪声的不变特征量提取和检测技术,水下语音、图像传输和抗干扰技术。同时概述,声纳设计的前沿领域:大孔径拖曳线列阵声纳、高分辨力合成孔径声纳、深海传呼机等的发展情况。 相似文献
7.
Ballard MS 《The Journal of the Acoustical Society of America》2012,131(3):1969-1977
An acoustic propagation model is applied to predict measurements of three-dimensional (3-D) effects recorded off the southeast coast of Florida. The measured signal is produced by a low frequency source that is towed north parallel to the shelf from a fixed receiving array. The acoustic data show the direct path arrival at the bearing of the tow ship and a second refracted path arrival as much as 30° inshore of the direct arrival. Notably, the refracted arrival has a received level more than 25 dB greater than that of the direct arrival. A geoacoustic model of the environment is created to explain the data. It is shown that the topography of the seafloor plays the largest role in controlling horizontal refraction effects, whereas the range-dependent sediment properties have the most influence on the received level. The modeling approach is based on a 3-D adiabatic mode technique in which the horizontal refraction equation is solved using a parabolic equation in Cartesian coordinates. A modal decomposition of the field provides insight into the variability in the arrival angle and received level of the measured signal. 相似文献
8.
针对拖曳线列阵声呐平台噪声构成近场强干扰影响声呐弱目标探测的问题,利用近场平台噪声的多途传播特性,将匹配场定位技术和平面波目标方位估计技术结合,使用平台噪声到达接收阵的拷贝向量以及平面波方向向量共同设计平台噪声零响应约束空域矩阵滤波器,实现了平台噪声抑制.推导得出滤波器设计最优化问题的最优解,利用广义奇异值分解简化最优解表达式,并给出滤波器对平面波方向向量整体响应误差以及对平台噪声拷贝向量响应。利用平台噪声拷贝向量与远场平面波方向向量相关性,解释了平台噪声构成强干扰的原因,以及滤波后存在探测盲区的原因。由仿真可知,空域矩阵滤波处理可获得更小的探测盲区,同时获得盲区外更高的探测能力. 相似文献
9.
基于线谱特征的三元组拖线阵左右舷分辨 总被引:1,自引:0,他引:1
传统的三元组拖线阵在分辨目标左右舷时利用左、右两侧的宽带能量之比,该技术在通常情况下能够较好地完成使命,但在实际应用中可能会遇到一些困难。本文针对两种影响其左右舷分辨结果的情况做了分析:一种是弱信噪比情况,另一种是另一舷侧存在强干扰目标的情况。针对这两种情况,通过对左、右舷频谱特征的分析,提出了利用线谱特征提取结果分辨目标左、右舷的新技术,显著降低了左右舷分辨功能对输入信噪比的要求。仿真和对海上实验数据的处理结果验证了该方法的稳健性和有效性,可望应用于工程实践中。为了使该技术能够适用于更低的信噪比条件,本文还提出了一种简单实用的线谱增强技术。 相似文献
10.
Estimating the bearing of a narrowband sound source using a towed horizontal array is a common array processing problem. This paper designs nonuniform linear symmetric arrays of fixed apertures for estimating the bearing of a sound source. Specifically, the hydrophone spacings for a symmetric linear array are chosen to maximize the upper bound on the mutual information between the true bearing and the estimated bearing in spatially white noise. The arrays maximizing the mutual information while nulling the forward endfire direction look significantly different from the uniform arrays commonly used in towed systems. Arrays maximizing mutual information are helpful when bearing estimation is considered as a quantization problem to assign the source to the correct partition. The optimal partitions for the array are designed using the Lloyd algorithm with an inner product distortion metric based on maximizing the likelihood function of the observations. In these approaches, increasing the mutual information and optimizing the partitions should reduce the probability of error (P(e)) in choosing the partition containing an unknown source. Simulation results with MAP and ML estimators demonstrate that the optimum arrays and partitions proposed here have a much lower P(e) than the uniform array and uniform partitions. 相似文献
11.
12.
Thode A 《The Journal of the Acoustical Society of America》2004,116(1):245-253
A passive acoustic method is presented for tracking sperm whale dive profiles, using two or three hydrophones deployed as either a vertical or large-aperture towed array. The relative arrival times between the direct and surface-reflected acoustic paths are used to obtain the ranges and depths of animals with respect to the array, provided that the hydrophone depths are independently measured. Besides reducing the number of hydrophones required, exploiting surface reflections simplifies automation of the data processing. Experimental results are shown from 2002 and 2003 cruises in the Gulf of Mexico for two different towed array deployments. The 2002 deployment consisted of two short-aperture towed arrays separated by 170 m, while the 2003 deployment placed an autonomous acoustic recorder in tandem with a short-aperture towed array, and used ship noise to time-align the acoustic data. The resulting dive profiles were independently checked using single-hydrophone localizations, whenever multipath reflections from the ocean bottom could be exploited to effectively create a large-aperture vertical array. This technique may have applications for basic research and for real-time mitigation for seismic airgun surveys. 相似文献
13.
14.
在深海声道条件下,海水折射效应会使得声场出现会聚效应;在不完全声道条件下,深海海底对声场具有重要影响.利用在中国南海海域收集到的一次深海声传播实验数据,研究了深海不完全声道环境下的海底反射对声传播的影响.实验观测到不同于深海会聚区的海底反射会聚现象,在直达声区范围内的海底地形隆起可导致海底反射会聚区提前形成,并使得部分影区的声强明显提高.由于不平坦海底和海面的反射破坏了完全声道环境下的会聚区结构,在60 km范围内存在两个海底反射会聚区,会聚区增益可达10 dB以上,同时在11 km附近的影区和51 km附近形成高声强区域.当接收深度与声源深度相同时,第二会聚区的增益高于第一会聚区.在第一会聚区内,随着接收深度的增加,声线到达结构趋于复杂,多途效应更加明显.使用抛物方程数值分析结合射线理论对深海海底反射会聚区现象产生的物理原因进行了分析解释.研究结果对于声纳在深海复杂环境下的性能分析具有重要的指导意义. 相似文献
15.
16.
17.
18.
Thode A Skinner J Scott P Roswell J Straley J Folkert K 《The Journal of the Acoustical Society of America》2010,128(5):2681-2694
Passive acoustic towed linear arrays are increasingly used to detect marine mammal sounds during mobile anthropogenic activities. However, these arrays cannot resolve between signals arriving from the port or starboard without vessel course changes or multiple cable deployments, and their performance is degraded by vessel self-noise and non-acoustic mechanical vibration. In principle acoustic vector sensors can resolve these directional ambiguities, as well as flag the presence of non-acoustic contamination, provided that the vibration-sensitive sensors can be successfully integrated into compact tow modules. Here a vector sensor module attached to the end of a 800 m towed array is used to detect and localize 1813 sperm whale "clicks" off the coast of Sitka, AK. Three methods were used to identify frequency regimes relatively free of non-acoustic noise contamination, and then the active intensity (propagating energy) of the signal was computed between 4-10 kHz along three orthogonal directions, providing unambiguous bearing estimates of two sperm whales over time. These bearing estimates are consistent with those obtained via conventional methods, but the standard deviations of the vector sensor bearing estimates are twice those of the conventionally-derived bearings. The resolved ambiguities of the bearings deduced from vessel course changes match the vector sensor predictions. 相似文献
19.
为了进一步增大光纤拖曳阵的探测距离,研制了缆径为16mm的32元分布反馈式光纤激光水听器拖曳线列阵.阵元在10~2 000Hz频率范围内的平均声压灵敏度为-142.7dB(re 1rad/μPa),波动幅度小于±2dB.基于声光调制器的时分、波分联合复用技术实现了32元光纤激光水听器的多路复用,各个阵元之间以及各个通道之间的串扰均小于-40dB,并完成了静态和动态拖曳湖上实验.实验结果表明,研制的32元分布反馈式光纤激光水听器拖曳线列阵无论是在静态,还是在6~16节的动态拖曳状态,都能对目标形成稳定的波束指向,与GPS轨迹记录完全一致,展现了分布反馈式光纤激光水听器拖曳线列阵在工程上的应用前景. 相似文献
20.
The performance of broadband sonar array processing can degrade significantly in shallow-water environments when interference becomes angularly spread due to multipath propagation. Particularly for towed line arrays near endfire, elevation angle spreading of multipath interference often results in masking of weaker sources of interest. While adaptive beamforming in a series of narrow frequency bands can suppress coherent multipath interference, this approach requires long observation times to estimate the required narrowband covariance matrices. To form wideband covariance matrices which can be estimated with less observation time, plane-wave focusing methods have been used to avoid interference covariance matrix rank inflation. This paper extends wideband focusing to the case of coherent multipath interference. The approach presented here, called waveguide invariant focusing (WIF), exploits a robust relationship for the frequency dependence of horizontal wave number differences. Unlike matched-field methods, WIF does not model multipath wave fronts but rather makes the interference appear to occupy the same rank-one subspace across frequency. This permits formation of wideband covariance matrices without interference rank inflation. Simulation experiments in a realistic ocean environment indicate that adaptive beamforming using WIF covariance matrices can provide a significant array gain improvement over conventional adaptive methods with limited observation time. 相似文献