浅海复杂多变的水文环境严重影响了水下目标辐射噪声特性,给航空声呐探测带来了巨大的挑战.在分析水下目标辐射噪声谱特征的基础上,讨论了浅海水文环境及其传播规律,基于波导不变性理论,对典型浅海环境条件下运动目标辐射噪声形成的时间-频率干涉谱进行了理论分析和仿真验证.结果表明:在Pekeris波导、负梯度和正梯度等典型浅海环境条件下,波导不变量存在差异,被动全向声呐浮标接收到的不同噪声谱声源信号具有明显的干涉特征.根据干涉谱和浅海环境参数信息可实现目标运动态势的判读.

为提高海上编队反潜能力,采用航空声呐浮标和舰载声呐多基地协同探测.从声呐方程出发,建立了搜索范围模型,定量分析了发射声源级和辐射噪声总声级对探测优势的影响.仿真结果表明,对于低噪声目标,辐射噪声级越小,发射声源级越大,协同工作模式相对于单基地模式搜索范围的优势越明显,对于高噪声目标,优势丧失.多基地搜索是应对低噪声水下目标威胁的有效手段.

针对现有简单模型对水下实际目标的仿真逼真度较差的情况,利用COMSOL声固耦合算法以及完全匹配层对二维潜艇简单模型受激励后的散射声场进行了数值仿真分析.利用ANSYS有限元分析软件对相同简化模型进行计算对比,计算结果基本吻合,验证了COMSOL在计算大型目标散射声场时的有效性.最后以某型潜艇结构为原型构建了内部舱室结构及结构材料属性,提高了模型相对于实际目标的逼真度,仿真了受激励后的再辐射声场.其结果可对水下主动探测装备发展提供参考.

针对船舶、潜艇等水声目标螺旋桨轴频自动提取困难的问题,提出一种基于平均能量累积和脉冲序列匹配的水声目标螺旋桨轴频特征提取算法,算法首先将噪声不同频段的调制信息利用多频段融合改进方法对DEMON谱进行线增强,然后利用平均能量累积方法对与螺旋桨轴频及其谐波相关的线谱进行提取,由于提取的线谱所对应轴频或谐波次数不明确,最后算法通过序列匹配方法计算线谱对应的谐波次数,从而实现螺旋桨轴频的自动提取,通过实验验证,算法取得了较好效果.

Some whale contact calls are mis-detected as ship-radiated noise by a ship's passive sonar due to their frequency bands overlapping.So,these whale calls should be detected correctly and eliminated to improve the further target autonomous recognition.Here,a two-stage whale calls detection algorithm was proposed.In the first stage,whale calls were modeled with the polynomial phase signal and the ship-radiated noise was modeled with the local stationary Gaussian random process after pre-whitened based on its frequency stability.Then whale contact calls were detected using the generalized likelihood ratio detection method based on matched filters.The test results based on a great many measured data showed that the proposed method is applicable for various types of ships;compared with another three detection methods,the proposed method is superior to the other three ones,and can achieve a higher whale calls detection rate under a certain false alarm rate.

This paper gives a method using virtual instruments technology to generate sonar signal by NI DAQ card and amplifying circuit .This paper gives an example of generating CWP signal .In design of software ,it generates signal by the way of timer querying and signal triggering .Existing method generates an array then delay to transmit .Method in-troduced in this paper ,by contrast ,is more flexible and has a higher degree of accuracy .Hardware design adopts stable and mature chips ,to make sure the system can perform well in outfield .Multiple strobe circuits achieve a wide range of SL .High-fidelity integrated power amplifiers reduce the distortion of the signal during transmission and the introduction of noise .Compared with traditional sonar signal transmitter ,the micro DAQ card and amplifying circuit can be put inside the industrial control computer ,used as a portable sonar signal transmitter .

The vocal mechanism and structure of ship radiated noise and marine biological noise are analyzed, and the differences of short-term inter-frame spectral similarity between the two kinds of noise are compared. On the basis of this, Pearson correlation coefficient variance of the spectral trend of the adjacent two frames in the short term of the framing signal is used as the recognition feature. A signal recognition method based on the similarity of short-time spectrum is studied to classify and indentify ship radiated noise and marine biological noise. The two kinds of noise are indentified based on the measured ship radiated noise signal and marine biological noise signal. And the recognition result proves the effectiveness of the method.

Spectral subtraction is wildly used in speech enhancement . But it is not always available in the ship working environment because of the fact that it is hard to discriminate the speech duration with the ship noise . So , in this paper , we propose a new approach , which first computes the frequency spectrum similarity and then discriminates the signal segments into speech or noise roughly . And then by the frame shifting method , we achieve a high discrimination precision . Finally , the improved algorithm is benchmarked on a large measured data and experimental results show that the proposed method can be used in various ship‐radiated noise environments . The discrimination accuracy is 98% for ship‐radiated noise and 96% for speech .

Aim at the operation problem of heterogeneous sensor bistatic system consisting of shipboard sonar and dipping sonar, a bistatic search model based on the sonar equation under ocean ambient noise is established. In the bi-static cooperative system, both shipboard sonar and dipping sonar receive underwater target echo signal, but the detec-tion signal is transmitted by shipboard sonar. Based on energy relationship, the extended search area, range and equiv-alent radius of bistatic cooperative system consisting of shipboard sonar and aerial dipping sonar are modeled. Influ-ences of factors such as source level and baseline length on the search area of the system are analyzed. Simulation re-sults show that when source level of shipboard is high enough compared with dipping sonar, the bistatic cooperative system outperforms monostatic cooperative system not only in search area but also in search width.

On the basis of analyzing physical mechanism of reliable acoustic path( RAP ) and time reversal processing is combined. Time reversal positioning problem of vertical hydrophone array based on RAP is researched. Simulation analysis under the condition of Munk sound speed profile is carried out,and the result shows validity of positioning of vertical line array based on RAP,improving sensor number and distance between sensors can enhance time-reversal energy focus effect.

Signal excess of bistatic sonar was analyzed from sonar equation.SE and detection probability was combined.The concept and calculation method of area track probability was put forward.The difference of track initialization performance for a sonobuoy array shape between monostatic and multistatic was compared.Simulation result shows the advantage of multistatic aerial sonobuoy centralized track is superior to monostatic distributed track.Area track initialization probability can be used to quantitatively evaluate multistatic sonobuoy array performance.

In this paper, the discrimination of speech and ship-radiated noise has been studied, for their interference with each other in the modern sea war, and a new feature abbreviated as SFSD (the Similarity of the Frequency Spectrum Distribution of two successive signal frames) is introduced. Based on the feature, a new two-stage approach is proposed, which firstly computes the SFSF and classifies the signal into speech or ship-radiated noise roughly, and then in the second stage, with the help of context smoothing, the signal are final discriminated in to speech or ship-radiated noise. The algorithm is benchmarked on a large measured data set, with correct recognition accuracy of 96% for ship-radiated noise and that of 92% for speech. Experimental results show that efficiency is exceptionally good.

针对评估水下传感器多基地系统水下监测能力时,经常缺少解析形式的搜索性能模型的问题,建立了一种目标航迹给定、传感器位置服从随机分布的多基地声纳搜索性能模型.该模型基于接收器探测距离的上边界得到系统成功搜索概率的计算方法.以声源/接收器位置服从均匀分布为例,计算了多基地系统的成功搜索概率解析解.将不同声源/接收器数目与探测次数条件下,该解析解的计算结果与蒙特卡洛仿真结果进行比较.仿真结果表明,二者具有很强的一致性,建立的搜索性能模型合理有效,可以为工程参数设计提供指导意义.

针对航空反潜磁异常探测传统探测宽度模型无法准确分析目标磁特性、环境磁特性等因素对航空磁探潜探测宽度的影响,引入概率分布的思想并提出基于信噪比检测依据的新探测宽度模型.为了求解该探测宽度模型,建立了基于磁偶极子目标的航空磁探潜探测模型,目标磁特性模型,环境噪声和检测模型,给出了基于信噪比检测依据的探测宽度模型求解方法和步骤.仿真分析表明:所建立的模型能够充分反映目标特性、地磁场特性、环境磁噪声等级、反潜机探测平台等因素条件对航空磁探潜探测宽度影响;与经典探测宽度模型相比,新建立的模型能够对航空磁探潜探测宽度进行更加有效和精确的计算.

基于简正波理论,利用宽带信号的频域分解与合成求解噪声信号的传播问题.在给定的战场态势和海洋环境下,研究了噪声干扰器的对潜开角、对潜距离、布放深度参量对干扰效果的影响,得到了在远场条件下,噪声干扰器的布放深度对干扰效果的影响要大于其对潜距离的影响结论.而在之前的研究中深度参量的影响一直是被忽略的.在此基础上,通过进一步计算得到了噪声干扰器的最佳布放位置和深度.

In a long time, the specialists in underwater acoustic countermeasure field were used to get an approximate evaluation of the transmission loss of noise signals by spreading loss equation of spherical wave, which led to results with a low accurateness. Based on normal mode theories and discrete Fourier transformation (DFT), derived the composition and process of the broadband acoustic propagation model. Then the transmission loss could be calculated via this propagation model, which could get a relatively more accurate result. The influence of three key positional parameters, the orientation, distance and depth of the noise-jammer were studied in this paper. The method and conclusions in this paper can provide a reliable foundation for tactical research on noise-jammers.

在航空反潜战中,合理有效地布放被动浮标阵是提高探测概率的关键.该文将遗传算法应用于优化被动浮标布阵,合理设计了交叉算子,变异算子和适应度函数等.仿真分析了按经验布放的传统浮标阵和GA优化阵形的探测效能,结果表明该算法在复杂水声环境条件下,能有效提高被动浮标阵的探测概率.

An underwater detection method for rapidly moving acoustic source in air was proposed. A underwater acoustic field excited with a rapidly moving acoustic source in air was modelled by a wavenumber integration method, and time domain waveform of the underwater received temporal signal was simulated and analyzed. The underwater noise of acoustic source in air is detected by the detector, which is obtained with bispectrum replacing discrete Fourier transformation of the signal, based on signal contiguity in time-frequency domain and characteristic of higher order spectrum inhibiting Gaussian noise. Results of the simulated and the processed in true data show that the proposed method is feasible.

The characteristics of air-to-water sound transmission should be considered when detecting in water.In this paper,the normal mode method was used to discuss the sound field in water of airborne source.And the sound field in water produced by airborne sound was simulated and analyzed.Then the normal mode method was compared with ray method and FFT for the sound field transmission loss in water of airborne source.The results show that the normal mode method suits for the simulation of far field transmission loss.