海上航船分布及其对海洋环境噪声的影响

当代水下目标探测向低频远程发展,海洋环境噪声的低频特性倍受关注,航船噪声是海洋中的主要低频噪声源。近几十年来,海上航运量迅速增长,导致海洋环境低频噪声大幅升高,增加了海洋环境的噪声污染。本文依据港口进出航船信息库和船舶自动识别技术数据库资料,分析历史航船分布数据,依据获得的某开阔海域航船分布规律,建立数值模型估计了航船噪声源对低频海洋环境噪声特征的影响。结果表明,日进、出港的航船数近似满足正态分布,近海开阔海域单位面积、单位时间内的航船数近似满足泊松分布;由于海上航船的影响,海洋环境噪声强度呈明显的水平非均匀分布状态。     

A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030

Ocean noise levels are thought to be increasing as a result of major growth in global shipping activity, but data quantifying those changes are limited in space and time. As an alternative approach, this study examines the current and future maximum noise capacity of three segments of the global commercial shipping fleet: container ships, oil tankers, and bulk carriers. It shows that continued growth in the number of ships, the quantity of goods carried and the distances traveled could increase the maximum noise capacity of the global shipping fleet by up to a factor of 1.9 by 2030, with major growth in particular in the container and bulk carrier segments. Thus, in the absence of operational or manufacturing changes to such ships, the contribution of commercial shipping to ambient ocean noise levels can be expected to dramatically increase.     

Depth dependence of ambient noise

Omnidirectional measurements of ambient noise versus depth in the Caribbean, Mediterranean, Arctic, Pacific, and Atlantic areas are presented. The shapes of the vertical ambient noise profiles spanning the water column at frequencies from 25 to 500 Hz are shown to be heavily influenced by passing ships. The qualitative features of average noise profiles measured by mid-water hydrophones can be explained with the aid of a straightforward model, and it is concluded that low-frequency omnidirectional ambient noise depth dependence is predictable. The sensitivity of the vertical noise profile to passing ships, coupled with noise predictability suggests that surveillance could be effected by a vertical string of hydrophones without coherent processing in areas of relatively light shipping.     

极低频海洋噪声与风的相关性研究

风通过影响海洋表面从而产生200 Hz以上的深海环境噪声,但有研究指出,通过风生表面波之间的非线性相互作用产生的驻波,能够与海床共振构成海底微震,从而产生10 Hz以下的噪声。针对这一新型风生噪声机制,本研究对威克岛海域10 Hz以下的极低频噪声进行了分析。比较了不同频率下海洋环境噪声功率谱级与风速的相关性,并讨论了风速和风向对设立在威克岛南北部二组水听器三联体信号的影响,结果表明2 Hz处的海洋环境噪声级与风速相关性最好,而风速和风向变化越剧烈海洋环境极低频噪声与风速风向的相关性越好。     

Large aperture digital acoustic array

A digital array of 120 acoustic channels 900 m in length has been constructed to study low-frequency (20-200 Hz) ambient noise in the ocean. The array may be deployed vertically or horizontally from the research platform FLIP and the array elements are localized with a high-frequency acoustic transponder network. The authors describe the instrumentation, telemetry, and navigation systems of the array during a vertical deployment in the northeast Pacific. Preliminary ambient noise spectra are presented for various array depths and local wind speeds. Ambient noise in the frequency band above 100 Hz or below 25 Hz increases with local wind speed. However, in the frequency band 25-100 Hz, ambient noise is independent of wind speed and may be dominated by shipping sources     

Depth dependence of noise resulting from ship traffic and wind

Under conditions of distantly generated noise, the noise level is found to decrease with depth in the mid-northeastern Pacific. These data show a decrease in noise level greater than 25 dB between critical depth and the ocean bottom. A result of this decrease is that locally wind-generated noise can be detected on near-bottom receivers for wind speeds less than 10 kn. It is shown that the noise level generated form local sources such as wind and nearby shipping is almost independent of receiver depth. The differences in spectra shape between the distant shipping noise and wind-generated noise and the low noise levels detected near the ocean bottom allow the measurement in the frequency band at 200-500 Hz of local wind noise level for wind speeds less than 10 kn     

南海某海域海洋环境噪声谱级风关特性分析

为探索南海某区域海洋环境噪声谱级与风场的相关特性,结合潜标海洋环境噪声数据及对应海域的海面风场再分析数据,计算各频段噪声级与风速相关系数及线性拟合函数。分析结果表明:400～1 000 Hz频段,海洋环境噪声谱级与海面风速的相关系数在0.5～0.8之间,达到中等相关。1 000～5 000 Hz频段,两者互相关系数大于0.8,达到高度相关。对海洋环境噪声谱级与对数风速的回归分析结果显示,1000～5 000 Hz频段,两者的线性函数关系显著;并且在1 000 Hz附近的拟合斜率最大,海洋环境噪声谱级对海面风速变化的灵敏度最高。     

远洋运输系统人因可靠性定量分析

远洋运输中可能发生的灾害性事故,如船舶碰撞、搁浅、腐蚀疲劳破坏、火灾、爆炸等,大多与人为失误和组织失误（HOE）有关.因此,进行远洋运输系统人因可靠性定量分析,对于运输系统的安全非常重要.针对此问题,文章结合操作风险管理（ORM）技术,对远洋运输系统进行人因可靠性定量分析.为远洋船舶提供了一套预测人为误操作的分析方法,可以降低HOE风险的发生概率,以减小事故的发生.     

Effects of sediment properties on surface-generated ambient noise in a shallow ocean

Surface-generalized ambient noise in a shallow ocean waveguide with a sediment layer possessing a specific class of density and sound speed distributions capable of describing a realistic seabed environment is considered in this analysis. This class of non-uniform sediment layer has the density and sound speed distributions varying with respect to depth as a generalized-exponential and an inverse-square function, respectively. The study invokes a formulation developed by Kuperman and Ingenito (Kuperman, W. A., Ingenito, F., 1980. Spatial correlation of surface-generated noise in a stratified ocean. J. Acoust. Soc. Am., 67, 1988-1996.) for surface noise generation, in conjunction with the analytical solutions for the Helmholtz equation corresponding to the sediment layer, to arrive at an analytical expression convenient for numerical implementation. The intensity and spatial correlation of the noise sound field are analyzed with respect to the variation of the system parameters, including frequency, sediment layer thickness, sound speed gradient, with emphasis on the effects of sediment properties on the ambient noise field. The results have demonstrated that the intensity of the noise field is relatively sensitive to the variation of the parameters, but the spatial correlation is affected to a less extent, suggesting that the energy distribution, rather than the spatial structure, of the noise field is more susceptible to the environmental variations.     

Measured vertical noise directionality at five sites in the Western North Atlantic

Solutions were computed for the vertical ambient sea noise field directionality at five sites in the Western North Atlantic Ocean using data from a 26-hydrophone element array with a 358.4-foot aperture at a center depth of 1,000 feet. Results show that the low-frequency noise below 100 Hz is concentrated near the horizontal (50 to 93 percent of the noise power between /spl plusmn/15/spl deg/ of horizontal) and is apparently dependent on bottom loss and shipping density. The results in the band 200 to 380 Hz are a combination of sea state and shipping noise dependent. A noise field solution technique was developed involving noise cross spectral matrix inversions. This technique overcomes some of the drawbacks of previous techniques such as least mean square estimation and successive approximations.     

Ship sources of ambient noise

The rapid increase in world shipping results in an increase in low-frequency ambient noise at an average rate of about 1/2 dB per year. During the past 10 years there has been a virtual revolution in the sizes and speeds of merchant ships, resulting in significant increases in the noise radiated by the average ship. This trend is continuing. In this paper, the trends in world merchant shipping will be presented, including important changes in propulsion plants as well as in numbers and sizes of ships. The need for radiated noise measurements of these new ship types will be stressed. Ambient noise is also dependent on the geographical distribution of shipping. The LRAPP-sponsored program to establish standard shipping distributions for the Northern Hemisphere will be discussed, and the reliability of current information will be assessed.     

Sequential Filtering for Surface Wind Speed Estimation from Ambient Noise Measurement

Many research results show that ocean ambient noise and wind speed are highly relevant, and the surface wind speed can be effectively inverted using ocean noise data. In most deep-sea cases, the ambient noise of medium frequency is mainly determined by the surface wind, and there is a conventional relationship between them. This paper gives an equation which shows this relationship firstly, and then a surface-wind inversion method is proposed. An efficient particle filter is used to estimate the speed distribution, and the results exhibit more focused close to the actual wind speed. The method is verified by the measured noise data, and analysis results showed that this approach can accurately give the trend of sea surface wind speed.     

北冰洋冰下环境噪声：长期冰站观测结果

本文利用中国第9次北极科学考察长期冰站自容水听器记录的数据对北冰洋冰下环境噪声进行了研究。通过对两段7秒长的冰层引起的噪声的时频分析表明：无论是冰层碰撞噪声还是冰层破裂噪声在时域都存在大量的峰值点（呈现脉冲特性）,在频域都存在丰富的频率分量。冰层碰撞噪声可以持续数秒,而冰层破裂噪声的持续时间要短得多（小于几十毫秒）。本文采用高斯分布和对称alpha稳态分布来拟合冰下脉冲噪声。对称alpha稳态分布可以跟踪脉冲噪声的重尾,从而获得更好的性能,而高斯分布则效果不佳。本文还分析了冰下环境噪声观测试验期间采集到的气象参数,推断出冰下脉冲噪声是由较高的风速和升高的大气温度共同作用于冰层造成的。本文还研究了冰下环境噪声长期的功率谱密度变化与气象参数之间的皮尔逊相关系数。     

Ambient noise measurements in the northwest Indian Ocean

Ambient noise measurements were made at seven different locations during the first four months of 1977. The measurement systems included: two types of towed arrays, a bottomed array, and systems with sensors distributed throughout the water column. The noise in the frequency regime dominated by shipping was found to be extremely high with a spectrum level of 92 dB//1 /spl mu/Pa at 50 Hz. These high levels were attributed to the high-density shipping. Horizontal directionality of the noise varied from site to site, ranging from highly directional to nearly nondirectional. The character of the directionality was highly dependent on the site position relative to shipping lanes. The noise showed very little dependence on depth.     

一种基于Curvelet变换的合成孔径雷达海洋内波图像的斑点噪声抑制方法

合成孔径雷达是海洋内波研究中最重要的工具之一。雷达图像中的斑点噪声会严重降低图像的质量,这一问题在处理和分析信号较弱的二模态内波信号和上升型内波信号时极为明显。合成孔径雷达图像中的海洋内孤立波的信号具有明显的尺度性和方向性。同时,curvelet变换作为一种同时具备尺度分辨率和方向分辨率的数学变换,能够对一幅雷达图像在不同尺度、不同方向和不同位置上进行分析。本文给出了一个基于curvelet变换的合成孔径雷达海洋内孤立波图像的斑点噪声抑制方法。该方法可简述为：(1)对一幅合成孔径雷达海洋内孤立波图像进行curvelet变换,获得curvelet系数;(2)分别仅仅保留一个尺度的系数,将其它尺度的系数置为零,利用处理之后的系数分别重建图像,得到仅仅用一个尺度的系数重建的图像;(3)分别计算上一步中得到的图像的均方差,根据波浪理论,图像的方差代表能量,方差越大则能量越大,以此可以确定内波信息集中的尺度;(4)在每个尺度下,分别计算每个方向的curvelet系数矩阵的平均值,以此确定内孤立波信号集中的方向;(5)在上两步工作的基础上,仅仅保留内波信号集中的尺度和方向的系数,而将其它尺度和方向的系数置为0,得到一幅提取主波信息的图像;(6)将上一步得到的提取主波信息的图像加回到原始图像中,从而达到增强波浪信息并抑制斑点噪声的目的。大量的实验验证表明,该方法不仅能有效地压制斑点噪声,而且能有效地增强波浪信号。     

Spatial processing of signals received by platform mounted sonar

Acoustic signals received by platform mounted sonar arrays can be spatially processed to enhance the detection of targets in the presence of both ambient and platform generated (self) noise. Ambient noise in the ocean, such as that due to distant shipping or biological choruses, are known to be spatially correlated. The platform generated noise will be of near-field origin and may not be received by all elements in the array. In this paper we investigate the performance of the minimum variance distortionless response (MVDR) beamformer and the recently introduced Fourier integral method (FIM) and compare their performances with the conventional beamformer. Real passive sonar data, obtained from a platform mounted sparse linear array of hydrophones, is used to study the performance of the beamformers in a typical sonar environment. It is shown that in the absence of self noise, when the array is accurately calibrated the MVDR beamformer will perform very well, but when sensor gain or phase errors are present the performance of the MVDR beamformer is degraded. Further, the MVDR beamformer is unable to reject the self noise which is not "seen" by the entire array. FIM however seems to perform well and a modified version of FIM, which we call weighted FIM (WFIM), is shown to perform better and is at worst comparable to a well calibrated MVDR beamformer     

Signatures of ocean storms on seismic records in South China Sea and East China Sea

Ocean storms on seismic records reveal coupling mechanisms between Earth’s spheres. We analyzed temporal and spatial signatures of ocean storms on seismic records in the South China and East China Seas. The main points are: (1) the landing of ocean storms directly influences spectrum amplitudes of microseisms, showing an “increase-peak-decrease” pattern, whereas they exert no direct influence on Earth’s hum and the high-frequency noise; (2) for microseisms, spectrum amplitudes of short-period double-frequency microseisms are increased greatly during ocean storms’ landing, implying that storms preferably excite short-period ocean swells; (3) while the “increase-peak-decrease” pattern of spectrum amplitudes is observed for both short-period double-frequency microseisms and long-period double-frequency microseisms in South China Sea, the peak arrived and disappeared much earlier for long-period double-frequency microseisms, which can be explained by their causal mechanisms; (4) in East China Sea, only the spectrum amplitudes of short-period double-frequency microseisms show an “increase-peak-decrease” pattern and extraordinary spectrum pulses are observed reflecting thick sediments there; (5) spatial features of microseisms revealed from predominant polarization directions indicate that local coastlines play very important roles in deciding where ocean waves impact; (6) high-frequency noise is caused by local offshore wind-generated ocean waves instead of ocean storms; (7) the influence of ocean storm landing processes on microseisms can propagate through continents and is observed at inland stations; (8) seismic motions are excited more efficiently in horizontal directions when ocean waves impact seafloors. Our work clearly exhibits how effectively local ocean events are coupled with the Earth’s lithosphere in Chinese seas.     

OBS海洋环境信号分析与应用

为研究海洋环境信号在OBS(Ocean Bottom Seismograph)原始数据中的规律及应用,根据OBS原始数据的波形及频谱特征,将研究区划分为5个时间段,依次为旧涌浪阶段、风浪渐强阶段、风浪全盛阶段、风浪消退阶段和新涌浪阶段。结合海洋天气预报,认为上述现象是由偏南风风浪对海流的影响造成的。参考野外地震数据采集记录班报,得到各阶段的时长和距离,计算风浪渐强、全盛和消退阶段OBS附近海流的平均速度。结果表明:OBS原始资料中浅海海洋环境噪音增强的主要因素是风浪,且风浪引起的噪音信号的波形变化特征是渐进式的;OBS可用于接收某种特殊阶段(如台风、海啸等)的噪音信号,并根据噪音信号的波形特征、频谱变化规律和持续时间估算该阶段的海流速度变化。     

Ambient Noise Analysis of Deep-Ocean Measurements in the Northeast Pacific

During the late 1960s and throughout the 1970s, the U.S. Navy conducted a series of ocean acoustic measurement exercises to support development of systems and techniques to detect nuclear submarines. The exercises and most of the technical documentation were classified. In 2003, a project was sponsored by the U.S. Office of Naval Research (ONR, Arlington, VA) to declassify documentation and demonstrate the capability to recover acoustic data recorded on magnetic tape. One of the exercises, known as CHURCH OPAL, was selected for demonstration of acoustic data recovery. The record on magnetic tape spanned a period of ten days in September 1975 from a vertical assembly of hydrophones at a site midway between Hawaii and California. This paper presents selected excerpts from a key report (Wittenborn, 1976) on ambient noise that previously was unpublished and unavailable for general distribution. The earlier work is augmented with more complete and detailed analyses of the recovered digital data using modern analytical techniques. Data acquired from the hydrophones below critical depth enabled isolation of ambient noise due to distant shipping and local wind. The frequency band of the acoustic analyses was 30-500 Hz. The wind component of the ambient noise was evaluated at frequencies lower than reported by Wenz (1962).     

基于RMF技术的远洋船舶定量风险评估方法研究

在远洋船舶运输中，设备失效是导致各类事故的一个重要因素。文中引人RMF技术，将其应用到远洋船队的定量风险评估中，以及时查找并消除设备方面的事故隐患。首先找出潜在的风险事件及相关风险因素，然后运用模糊综合评判方法和事故损失综合评估理论对设备风险事件的模糊概率和损失程度后果进行量化，最后依据风险评价结果对需要控制的风险源给出控制措施。实例分析亦表明，运用RMF技术能对远洋船舶的各类设备及属具实施科学的风险管理。