Acoustic Countermeasure Research Articles

Data augmentation based on highlight image models of underwater maneuvering target

With the development of underwater acoustic countermeasure technology, deep learning is applied to recognize echo geometry features of underwater targets, but it faces the problem of sample scarcity. In this paper, we improved the underwater target highlight model, and established the target echo information equation of active sonar. By changing the spatial positions of target and sonar regularly, we performed the highlight image models of underwater maneuvering targets. Taking an underwater vehicle as an example, the model construction process was introduced in detail, and highlight image models of four typical acoustic scale decoys were also established, and five multi-space state highlight image data samples were generated. The eHasNet-5 convolutional classification network was designed, and the network was trained, verified and tested with the generated data. Finally, the experimental data test shows that the target highlight image generation models provide a new data augmentation method for the application of deep learning in active sonar target recognition, and the trained network by generated data has the ability to classify two-dimensional objects.

Towed Acoustic Countermeasures for Defending Acoustic Homing Torpedoes

The growing torpedo threat to ships and submarines demands effective countermeasures for defence. Detection, classification and localisation of an attacking torpedo is the first step towards launching effective countermeasures. Studies are on the rise to use the existing sonar systems to detect torpedoes and subsequently use countermeasures. The use of towed array sonar systems for torpedo detection and acoustic counter measures are the most recent and not reported much in open literature. This paper presents a modular acoustic counter measure approach using towed decoy against acoustic homing torpedoes. Describes the technologies and algorithms required for different modes of towed decoy, which is effective against both active and passive acoustic homing torpedoes. Towed decoy signal generation schemes and their realisation using digital signal processing hardware are outlined in this paper.

Research on the Optimization Design of Acoustic Stealth Shape of the Underwater Vehicle Head

The acoustic stealth shape design of the underwater vehicle has become a topic of considerable current interest to the experts engaging underwater acoustic countermeasure technology in recent years. During tracking the target, the echo strength of head shape is easily exposed and detected for the underwater vehicle, which directly affects its acoustic stealth performance. This paper proposes an optimal design method for the acoustic stealth shape of the underwater vehicle head with relatively lower target strength (TS), based on the Nelder–Mead optimization algorithm and finite element method. In this method, Bernstein polynomials are used to describe the underwater vehicle head shape deviation, and the optimization objective function is given as the weighting function of the TS of underwater vehicles head with different angles and frequencies. Then, the two optimized results with different situations are given, which are evaluated using the angle detecting rate. Finally, the 2D axisymmetric calculation method of the underwater acoustic scattering field is used to verify the TS calculation in this paper. The optimization design method may provide guidance for the lower TS shape design of the underwater vehicle, which may realize the automatic design of the lower TS shape with incident plane waves at given angles and given frequency bands.

Ia-PNCC: Noise Processing Method for Underwater Target Recognition Convolutional Neural Network

Underwater target recognition is a key technology for underwater acoustic countermeasure. And how to classify and recognize underwater targets according to the noise information of underwater targets has been a hot topic in the field of underwater acoustic signals. In this paper, the deep learning model is applied in the underwater target recognition and the improved anti-noise Power-Normalized Cepstral Coefficients (ia-PNCC) is proposed based on PNCC oriented to underwater target noise features. In this coefficient, multitaper and normalized Gammatone filter group are used to improve the anti-noise capacity of PNCC in underwater target recognition, and it is combined with the convolutional neural network to recognize the underwater target. The experiment results show that the acoustic feature presented by ia-PNCC is of higher anti-noise capacity and more adaptive to the underwater target recognition model of convolutional neural network. Compared with the combination of convolutional neural network with single acoustic feature such as MFCC (Mel-scale frequency cepstral coefficients) or LPCC (Linear Prediction PLP) and so on, the combination of ia-PNCC with convolutional neural network improves the underwater target recognition accuracy greatly.

A Study on Improvement of Submarine Torpedo Acoustic Counter Measure Launcher System Safety Device Performance

A Study on Improvement of Submarine Torpedo Acoustic Counter Measure Launcher System Safety Device Performance

Study on acoustic improvements by sound-absorbing panels and acoustical quality assessment of teleconference systems

With the development of information and communications technology, conferences and remote education using teleconference systems have become common. When a teleconference system is used, the sound heard in a receiving room includes the acoustic characteristics of both the utterance and receiving rooms, in addition to the characteristics of the transmission via the teleconference system and Internet. Even today, when the digital technology is widely used, quality problems related to sound transmission remain; in particular, the influence of the reverberation of the conference room causes deterioration of the sound quality. Studies aiming to improve the quality of the signal transmission have been conducted; however, there are no acoustic countermeasure methods considering the acoustic characteristics of the two rooms connected by a teleconference system and performing the sound quality evaluation. In this study, focusing on a teleconference system sharing video and audio between two separate rooms, we evaluated the improvement in the sound transmission performance due to the addition of sound absorption to the conference room by examining the correspondence between the subjective assessment results and acoustical physical indexes. Additionally, the acoustical physical indexes that allow evaluating the quality of the sound transmitted via the teleconference system were also examined by comparing with the result of a subjective assessment. Intelligibility tests were conducted, listening difficulty ratings were evaluated, and the impulse response, STI, Clarity (C50), and reverberation time were measured in an actual teleconference system. We observed that, before the addition of sound absorption, the sound was difficult to listen to due to the acoustic characteristics of both of the utterance and receiving rooms. However, by suppressing reverberation in both the utterance and receiving rooms by using sound-absorbing panels, the difficulties in listening was improved. By examination of the correspondence between the subjective assessment results and acoustical physical indexes, we proved that STI and Clarity (C50) are highly correlated with intelligibility. On the other hand, reverberation time was found to be uncorrelated with the intelligibility of the rooms of teleconference systems.

Research on the Combination of Underwater Acoustic Countermeasure Equipments Against Torpedo

Today the use of acoustic countermeasure equipment has become the main means in submarine defense torpedo operation. Combination of acoustic countermeasure equipments are used during the operation so that we can amplify the countermeasure effect. Based on the subject of the acoustic countermeasure equipments’ combined use, this paper analyses the interference between these soft kill countermeasure equipments including gas curtain, acoustic decoy and acoustic interferometer, summarizes the advantages and disadvantages of the different combined use of acoustic countermeasure equipments.

The Application of Multi-Hypothesis Targets Algorithm in Track Association

Track association is an important role in torpedo anti- acoustic countermeasure. This paper put the multi-hypothesis targets algorithm which based on kalman filter theory into application of multi- targets track association. Data simulation experiment proved it that multi-hypothesis targets algorithm can effectively solve the measurement target data association problem .The target track can also be affirmed in short time

Simulation of Underwater Target Echo Based on Highlight Model

This paper describes that at high frequencies the reflection signal from an underwater target can be seen as the sum of an individual echo from certain equivalent scattering centers as such an underwater target can be characterized by highlights distributed within a spatial target structure. By analyzing the highlight structure of an underwater target echo, the synthesized echo signal can be simulated. In this paper, a submarine model is selected to analyze the echo characteristic of submarine based on highlight model. The simulation experiment results show that the model is a very reasonable two-dimensional acoustic representation of a submarine. The results also indicate that the highlight model can be applied to acoustic countermeasure system, which has an important application value.

The Influence of Positional Parameters on the Effect of a Noise-Jammer Based on Broadband Acoustic Propagation Model

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.

Research on Anti-Mine Acoustic Countermeasure Simulation System Based on HLA

This design of the anti-mine acoustic countermeasure simulation system based on HLA was proposed for the requirement of anti-mine combat simulation. Following the technique frame of HLA, the composition and characteristic of the system were analyzed, and the general framework of acoustic countermeasure simulation system was given. The implementation of federates was explained by describing the framework of federation, flow chart and FOM/SOM of federation. And the problem should be paid attention to was proposed at last. The simulation system laid the foundation for the acoustic magnetic combined countermeasure system.

표적 회피기동과 어뢰음향대항체계를 고려한 경어뢰의 효과도 분석

어뢰 개발 단계에서는 어뢰의 성능 예측과 운용 방법 습득을 위해 효과도 분석이 실시되고 있다. 이 때 신뢰성 있는 데이터를 획득하기 위해서는 전술 상황을 실제에 가깝게 모델링한 시뮬레이션 프로그램이 필요하다. 경어뢰의 경우 잠수함을 주요표적으로 삼고 있는데, 잠수함의 어뢰 대항 수단인 회피 기동이나 어뢰음향대항체계(TACM)를 상세히 모델링해야 신뢰성 있는 효과도 분석 결과를 획득할 수 있다. 본 논문에서는 잠수함의 운동 특성을 반영하여 회피기동을 모델링하였으며 부유식 기만기, 자항식 기만기, 재머(jammer) 등 다양한 음향대항체계를 고려하여 잠수함 표적을 모델링하였다. 그리고 이러한 모델링을 통해 개발한 시뮬레이션 프로그램을 이용하여 경어뢰의 효과도를 측정하고 분석하였다. In the development phase of a torpedo, the effectiveness analysis is carried out to predict the performance and to learn how to use the torpedo. In order to obtain reliable data, it is required to model the tactical situation closely to the actual one. Because the submarine is a target of a lightweight torpedo, the anti-torpedo countermeasures of a submarine such as evasive maneuvering and TACM (Torpedo Acoustic Counter Measure) should be modeled in detail. In this paper, the evasive maneuvering is modeled reflecting the movement characteristics of the submarine. Furthermore various TACMs such as a floating-type decoy, a self-propelled decoy and jammers are also modeled. Then, effectiveness of a lightweight torpedo is measured and analyzed using the simulation program which is developed through the above modeling procedure.

수상함의 배치에 따른 대잠 방어계획 효과도 연구

In this paper, the result of study on the effectiveness of anti-submarine defense plan according to the disposition of surface ships has been proposed. The surface ship carries a hull mounted sonar(HMS) as a underwater sensor and a torpedo acoustic counter measure(TACM) as a soft-kill weapon against torpedo attacks from the enemy. Nowadays these underwater systems have been combined into a integrated anti-submarine warfare combat system. And in the real anti-submarine operation environment, several surface ships cooperate for executing ASW plans. Considering these ASW systems and the ASW environment, the models of underwater systems mounted on an surface ship and the a general model of anti-submarine defense plan are proposed. And we designed a scenario for conducting simulations to evaluate the ASW plan according to the variation of the range and the relative angle between surface ships and a capital ship. The simulation results show the effectiveness of ASW plan depends on the formation of surface ships and a capital ship.

Acoustic sensing countermeasure device and method of determining a threat direction

An acoustic sensing countermeasure device is used to sense the direction of a threat projectile or vehicle in addition to countering the threat with noise or interference signals. Countermeasure device includes an acoustic receive array comprised of segmented vertical staves preferably mounted within a reduced diameter section around the outside housing of the countermeasure device. The staves are grouped to form directional acoustic beams across the entire horizontal plane. To determine the direction of the acoustic signals from the threat projectile or vehicle, the countermeasure device uses a method wherein the direction is indicated by the output of the directional acoustic beams. The countermeasure device locates a known reference direction used to determine the bearing of the threat. The bearing information can be transmitted, for example, to the vessel that deployed the countermeasure. In one example, the countermeasure includes a compass and the compass heading of North is used as the reference direction. Alternatively, countermeasure device can detect the vessel or another countermeasure device and use that as the reference direction.