水下目标对海洋环境噪声场的扰动特性
文献类型：学位论文
| 作者 | 王彦 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-05-15 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 海洋噪声 扰动 目标声学可见度 |
| 其他题名 | Disturbance to ambient sea noise field caused by submerged object |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | 近年来，随着贴敷消声瓦安静型潜艇的出现，人们注意到，可以利用海洋环境噪声作为“照明声源”来探测水下目标，此时环境噪声既是信号场，又是背景干扰场。利用环境噪声探测水下目标，不需发射声波，信噪比相对稳定，隐蔽性好，在某种程度上兼有主动、被动声纳两者的优点，并可能开拓新的使用范围，是一种值得探索的新型水下目标探测方法。 本文旨在从理论上初步研究水下目标对环境噪声的扰动特性，获得目标在环境噪声照射下的可见度及目标散射扰动的方向特性，为进一步了解、探索新型水下目标探测方法及其信号处理方案，提供必要的理论基础。利用海洋环境噪声探测目标，在各种海事作业和军事方面具有广泛应用前景。作为该新探测方法的理论研究，探讨水下目标对环境噪声的扰动特性，具有较重要的理论价值和学术意义。 论文首先介绍利用环境噪声探测水下目标的研究背景及意义、扼要综述国外在这一新方法探索过程中所进行的实验研究和理论研究。然后提出本文的研究思路：着重考虑无限海面噪声源这一主要的关键因素，采用较为经典的散射理论方法来讨论目标对噪声场扰动，并指出海面噪声是探测目标的主要“照明”声源。 文中在幅度高斯型相关函数单极子海面噪声源的假定下，引用单极子源半无穷空间格林函数的球函数展开式和任意分布声源声场的积分表达式，建立水下目标对海洋环境噪声的散射扰动模型，得到有目标时海洋中两接收点总噪声场协方差表达式。在此基础上将目标扰动理论模型推广到偶极子海面噪声源，并初步探讨海底的影响。 利用得到的理论表达式，数值模拟计算了水下目标散射强度的方向特性和声学可见度。结果表明：(1)在海面源为主的环境噪声“照射”下，刚球目标的散射方向特性和平面波入射显著不同，如： 时，入射声波前进方向有较明显的散射成分；(2)当存在目标时，两接收点总噪声场协方差中增加了散射噪声的贡献，并包含直达与散射间干涉成分，导致目标的声学可见度起伏变化。在所估算的较近距离范围内，目标声学可见度总的趋势是随与目标的距离下降，其均值约为4～5dB，与国外Buckingham的实验结果（矩形目标，宽0.77米，高0.9米，接收点距目标7米，频率9千赫）相近；(3)当噪声源均匀分布于海面（或海面下一无限平面）上时，在小偶极矩情形下，海洋环境噪声取偶极子海面噪声源模型还是单极子海面噪声源模型，对散射方向特性和声学可见度影响不大；(4)考虑海底影响时，刚性目标球对环境噪声散射强度的方向特性产生显著变化，随着海底反射系数的减小，海底的影响明显减弱。 关键词：海洋噪声 扰动 目标声学可见度 |
| 英文摘要 | Abstract: In recent years, along with the emergence of quiet submarines, people start to notice that ambient sea noise can be used to detect submerged objects; therefore, sometimes ambient noise field is not only background field but also signal field. This technology is very safe, for it is unnecessary to transmit any signals, however it gives the relatively stable SNR. To some extent, ambient sea noise detecting technology combines the advantages of both active sonar and passive sonar, and it has great potential to exploit a new application area. So it seems that this is a new underwater detecting method which is worth investigating. This paper is aimed at theoretically studying the disturbance to ambient noise field caused by submerged objects, obtaining visibility of object which is lighted by ambient noise and directionality of object scattering field, which will provide necessary theoretical bases for developing the new underwater object detection technology further in the future. This technology will have great potential in military areas and maritime affairs. As a theoretical research foundation of this new detection method, studying the disturbance of ambient noise field caused by submerged objects has very important theoretical value and academic meaning. In the beginning of this paper, the background and purpose for investigating ambient noise detecting technology are given. And some experimental and theoretical researches which have been done for exploring this new method are introduced briefly. The idea is illustrated that infinite surface noise sources and classical scattering theory will be used. It is considered that infinite noise sources distribution is the most important factor which is very different from other detecting methods, and surface noises are regarded to be the main sources that light on the submerged object. Assuming that the surface monopole noise sources have Gaussian-correlation amplitudes, we use the spherical function expression of Green function for monopole in semi-infinite space and the integral expressions of sound field for any source distribution to develop a theoretical model of disturbance of ambient noise by submerged object, and obtain the covariance expression of total noise fields at two receivers when there existed an object. Above model is extended to dipole sources distribution situation, and effects of seabed were also discussed. Calculating by using the above theoretical expressions, we get some numerical results as follows: (1) The directionality of object scattering is apparently different from plane-wave incidence when the object is lighted by ambient noise from ocean surface. For instance: when ka =1, there exists apparently scattering components in the direction of incident wave. (2) When there exists an object, the covariance between total noise fields of two receivers is added by the contributions from scattering field. And it contains intervening items between incident noise field and scattering field, which results in the fluctuations of acoustic contrast. In short range, the changing trend of acoustic contrast decreases with the distance between object and receiver. The mean value of acoustic contrast is 4~5dB, which is close to Buckingham’s measurement result. (3) When noise sources are uniformly distributed on the sea surface (or on the infinite plane below sea surface), for short dipole distances, the directionality of scattering and acoustic contrast does not change obviously no matter when using monopole or dipole sources distribution. (4) When the effect of seabed is considered, the scattering directionality of rigid spherical object lighted by surface noise will change greatly, and the effect will be weakened when the reflection coefficient of seabed decreases. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 63 |
| 源URL | [http://159.226.59.140/handle/311008/402]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 王彦. 水下目标对海洋环境噪声场的扰动特性[D]. 声学研究所. 中国科学院声学研究所. 2008. |
入库方式： OAI收割
来源：声学研究所
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