【作者】 胡鹏涛；

【导师】 杨德森；

【作者基本信息】 哈尔滨工程大学 ， 水声工程， 2010， 博士

【摘要】 随着声隐身技术的不断发展,低噪声潜艇的辐射噪声源级已接近于海洋环境噪声,这给辐射噪声测量带来了很大的困难,研究和解决符合我国国情的安静型潜艇辐射噪声测量技术,是摆在我们面前艰巨而紧迫的任务。我国大陆架较平缓,沿海多为浅海,很难找到具备建设深水试验场的海域,为满足安静型潜艇辐射噪声测量的需求,在浅海近距离测试比较适合我国国情。然而,我国这种特定的辐射噪声测量环境和潜艇复杂的声源结构及其辐射特性,使得测试海域内声场分布不均匀。当影响潜艇辐射噪声测量精度的诸多因素如测量设备,测距,测量方法等已得到很好解决时,测试海域内声场能量分布的不均匀性已成为影响我国潜艇辐射噪声测量精度的一个重要因素。基于此,本文以低噪声测量系统的实际工程项目为研究背景,对水下目标辐射噪声测量距离内的声场特性进行系统、全面的理论和试验研究。本文首先根据射线声学理论,推导了典型声源和复杂声源在边界约束条件下的声压场和质点振速场数学表达式,建立了基于虚源法的浅海矢量声场计算模型,并将声场计算模型应用于宽带声源信号矢量声场计算中,对于斜率变化平缓、表面起伏方差不太大的不平整表面,采用微扰法对其声场进行描述,为测试海域内声场特性研究提供理论计算方法。本文从潜艇辐射噪声测量的实际工程角度出发,研究了浅海环境下目标辐射声的矢量声场近程传播特性,揭示了测试海域内声场分布的不均匀性与目标声源结构及其辐射特性,声信号的频率、带宽,边界约束,海底声学特性,声源的空间位置,目标声源的航行工况等因素之间的相互关系。为了减小特定测量环境内声能量分布不均匀性对测量的影响,试验时需根据测量环境和测试目标,进行海域的声场空间分布分析,可选取声源与接收器合适的空间位置,在声能量汇聚程度较小的区域进行测量试验,提高测量的精度。本文将测试环境下的测量值与球面波扩展规律进行对比,定量分析了声能量分布不均匀引入测量误差的大小。传统的利用球面波扩展规律对辐射噪声测量值进行修正的方法,在远场自由场条件下是可行的,在近距离测量范围内对于无指向性的声源,也是可行的。但是对于有指向性的声源,或者存在边界约束时,利用球面波扩展规律对测量数据进行距离修正是有偏差的,特别是对于声能量抵消的区域,测量值和球面波扩展规律都远大于真值,此时需根据声源的辐射特性和空间位置进行特定修正。针对测试环境内声能量分布不均匀的主要影响因素,本文探讨和研究减小测试环境内声场分布不均匀的方法和相关技术,进一步提高测量精度。提出并从理论上证明了采用基于矢量水听器阵列测量模型的技术,能对信道空间传递函数平滑,为如何减小测试海域边界约束引起的声能量分布不均匀对目标辐射噪声测量的影响提供了依据；而利用分频带目标等效声中心估算和距离修正的方法,通过合理选取现实复杂声源的等效声学中心,能减小测量时体积分布源对目标辐射噪声测量结果的影响。通过系统地开展水下声传播近程测量试验,完成了矢量水听器的灵敏度校准及外场测试系统的方案设计,验证了水下目标辐射噪声测量距离内的声场能量分布不均匀特性、相关规律以及如何减小声能量分布不均匀对目标辐射声测量影响的方法,为实际工程测量的数据分析和矢量水听器阵列在水下目标辐射噪声测量中的工程应用提供了试验基础。更多还原

【Abstract】 With the constantly development of acoustic stealth technology, the radiated noise level of low noise submarine has already approached the ocean ambient noise, which brought great difficulty for radiated noise measurement. It is a difficult and urgent task for our country to research radiated noise measurement technology for quiet submarines which is consistent with our national conditions.As continental shelf of China is comparatively gentle and coastal areas are mostly shallow, it is difficult to find appropriate ocean area to build deep-water testing site. To satisfy the requirement of quiet submarine radiated noise measurement, it is more appropriate for China to test within short range shallow water. However, distribution of acoustic fields is quite inhomogeneous because of the short range shallow water environment, submarine’s complicated acoustic source structure and its radiated characteristics. Since great improvements have been made on the factors influencing accuracy of submarine radiated noise measurement, such as measurement equipments, ranging, approaches and so on, inhomogeneous distribution of acoustic energy in measuring sea has become an important factor influencing accuracy of submarine radiated noise measurement in China. Based on this, taken the practical engineering program of low noise measurement system as background, this paper does comprehensive theoretical and experimental investigation on underwater acoustic focusing characteristics within radiated noise measuring distance of target.Based on Ray Theory, mathematical expressions of sound pressure field and the particle velocity field were deduced for typical acoustic source and complicated acoustic source under the condition of boundary constraint. This paper came up with a calculating model of the vector acoustic field in shallow water using the image source method. The model was established and applied to the vector acoustic field computation when sound sources were broadband signals. Method of Small Perturbation (MSP) was applied to describe the acoustic fields of uneven surface with smooth slop and small fluctuation variance, which provided theoretical calculating methods for acoustic field’s characteristics research within testing sea.Characteristics of short-range vector propagation of target radiated sound in shallow water have been studied from the aspect of practical engineering in submarine radiated noise measurement, which shows that the inhomogeneous distribution of acoustic fields in testing sea is related to many factors like target sound source structure, radiation directivity, the band width and frequency of the signals, boundary constraint, seabed acoustic properties, the spatial location of sound sources, navigation condition of target acoustic sources and so on. In order to reduce the influence on measurement caused by inhomogeneous distribution of acoustic energy in specific measurement environment, acoustic field’s spatial distribution analysis has been conducted according to testing environment and testing targets. Measurement accuracy could be improved by choosing appropriate spatial location of acoustic source and receiver in areas with less acoustic energy convergence.The degree of measurement error caused by inhomogeneous distribution of acoustic energy has been quantitatively analyzed by comparing measurement results in measurement environment with spherical wave propagation law. It is feasible to correct radiated noise measurement results by using spherical wave propagation law in the far fields and free fields.It is also feasible for non-directional acoustic source within the short measurement distance. But when it comes to directional acoustic source or when boundary constraint exists, there is deviation in distance correction of measurement results by using spherical wave propagation. Measurement results and spherical wave propagation law are much larger than the true results especially for the acoustic energy offset areas.There needs to be specific correction according to radiated characteristics and spatial location of acoustic source.Toward the main influencing factors of acoustic energy inhomogeneous distribution in testing environment, this paper probed into methods and related technology for reducing inhomogeneous distribution of acoustic fields to further improve measurement accuracy. It is put forward and theoretically proved that the measurement model based on vector hydrophone array can effectively smooth the channel space transfer function, which provided a basis for how to reduce acoustic energy inhomogeneous distribution’s influence on target radiated noise measurement caused by boundary constraint of the testing sea. By estimating target equivalent acoustic center in different frequency bands and distance correcting, it is feasible to reduce the influence on results of target radiated noise measurement caused by volume distribution source through rationally selecting equivalent acoustic center of the practically complicated acoustic source.By systematical experiments on acoustic propagation measurement in short range, we have finished sensitivity calibration of vector hydrophone, out field testing system design, and validated the characteristics of acoustic energy inhomogeneous distribution within underwater target radiated noise measurement distance, related laws and methods on reducing acoustic energy inhomogeneous distribution’s influence on radiated noise measurement, which provided experimental basis for data analysis of practical engineering and engineering application of vector hydrophone array in underwater radiated noise measurement.更多还原