Accurately estimating the bearing of a target with two hydrophones requires knowing the precise distance between them.However,in practice,it is difficult to measure this distance accurately due to the influence of cur...Accurately estimating the bearing of a target with two hydrophones requires knowing the precise distance between them.However,in practice,it is difficult to measure this distance accurately due to the influence of current.To solve this problem,we propose a method for extracting the time-domain Green's function between two points in multi-ship scenarios and for extracting the time-domain waveform arrival structure between two hydrophones in real-time based on long samples of ship radiation noise cross-correlation.Using the cross-correlation function of the radiated noise from any ship located in the end-fire direction of the two hydrophones,we can estimate the distance between the hydrophones in real-time.To verify the accuracy of our estimation,we compare the result of azimuth estimation with the actual azimuth based on the azimuth estimation of a cooperative sound source in the maritime environment.Our experimental results show that the proposed method correctly estimates the distance between two hydrophones that cannot be directly measured and estimates the position of a cooperative sound source 4 km away with an average deviation of less than 1.2°.展开更多
By investigating the effects on deep ocean ambient noise of typhoon ＂KAI-TAK＂ which passed the north area of the South China Sea,it is shown that the wind speed,the rainfall intensity and the long wave swell caused ...By investigating the effects on deep ocean ambient noise of typhoon ＂KAI-TAK＂ which passed the north area of the South China Sea,it is shown that the wind speed,the rainfall intensity and the long wave swell caused by typhoon affect the ocean ambient noise significantly.The correlation between the ocean ambient noise and the wind speed during the typhoon is much better than that in the non-typhoon period in the same Beaufort scale.Analysis of the correlation between the 415 h ocean ambient noise measured data and wind speed shows that,when the frequency is greater than 300 Hz,the correlation coefficient between the ocean ambient noise and the wind speed is greater than 0.5,achieving a moderate correlation;when the frequency is greater than 630 Hz,the correlation coefficient is between 0.8 and 0.9,achieving a high degree of correlation.The correlation between the ocean ambient noise and the wind speed is better than that between the ocean ambient noise and the significant wave height when the frequency is greater than 300 Hz.The correlation between the ocean ambient noise and the wind speed in infrasonic band from 10 Hz to 20 Hz is poor in the South China Sea,because the shipping is busy in this sea area and the ocean ambient noise is contaminated by the ship noise even during the typhoon.展开更多
The effect of the correlation function of noise sources derived from the ocean wave spectrum on the vertical spatial correlation of ocean ambient noise is investigated. The spatial correlation models of ocean ambient ...The effect of the correlation function of noise sources derived from the ocean wave spectrum on the vertical spatial correlation of ocean ambient noise is investigated. The spatial correlation models of ocean ambient noise usually assume that the surface noise sources are uncorrelated. This assumption can be used to explain some physical phenomena, but it is not consistent with the real situation. Considering the relation between the ocean wave motion and the ambient noise generated by wind, the spectrum of ocean wave is introduced to calculate the vertical correlation of ocean ambient noise as the correlation function of noise sources by using the Kuperman-Ingenito （K/I） noise model. The comparison of the simulations and the experimental data shows that the simulations of vertical correlation of ambient noise have some differences with the experimental data by assuming the noise sources are uncorrelated and the simulations of vertical correlation of ambient noise have a good agreement with the experimental data by using the correlation function of noise sources derived from the ocean wave spectrum under the situation of high wind speed.展开更多
Physiological and behavioral systems exist to reduce the stress that the intertidal fauna may face during the unsuitable tidal phase. Cerithidea decollata is a common western Indian Ocean mangrove gastropod. It feeds ...Physiological and behavioral systems exist to reduce the stress that the intertidal fauna may face during the unsuitable tidal phase. Cerithidea decollata is a common western Indian Ocean mangrove gastropod. It feeds on the ground at low tide, and climbs the trees two-three hours before the water arrival to avoid submersion. Moreover, it regularly settles on the trunk roughly 40 centimeters above the level that the water will reach, in spite of the irregular East African tidal pattern. Migration usually takes place about twice a day unless at Neap Tide, when snails may remain on the dry ground. Biological clock cannot account for water level foreseeing while direct visual cues or chemical information from the water itself or from previous migrations have already been experimentally discarded. Indirect cues could be hypothesize related to the effect of the oceanic wave reaching the coast and the barrier reef (seismic noise), or alternatively related to changes in ground resistivity (self potential) caused by the sea water moving close. To verify these hypotheses a seismic noise and self potential survey was carried out at Mida Creek (Kenya). This paper presents the first results of the seismic noise measurements. A significant correlation between the time evolution (mean value) of the low frequency seismic signal, tides, and snails movements has been identified.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.62171148)。
文摘Accurately estimating the bearing of a target with two hydrophones requires knowing the precise distance between them.However,in practice,it is difficult to measure this distance accurately due to the influence of current.To solve this problem,we propose a method for extracting the time-domain Green's function between two points in multi-ship scenarios and for extracting the time-domain waveform arrival structure between two hydrophones in real-time based on long samples of ship radiation noise cross-correlation.Using the cross-correlation function of the radiated noise from any ship located in the end-fire direction of the two hydrophones,we can estimate the distance between the hydrophones in real-time.To verify the accuracy of our estimation,we compare the result of azimuth estimation with the actual azimuth based on the azimuth estimation of a cooperative sound source in the maritime environment.Our experimental results show that the proposed method correctly estimates the distance between two hydrophones that cannot be directly measured and estimates the position of a cooperative sound source 4 km away with an average deviation of less than 1.2°.
基金supported by the Natural Science Foundation of Fujian Province of China(2016J01019)the Public Science and Technology Research Funds Projects of Ocean(201305038)
文摘By investigating the effects on deep ocean ambient noise of typhoon ＂KAI-TAK＂ which passed the north area of the South China Sea,it is shown that the wind speed,the rainfall intensity and the long wave swell caused by typhoon affect the ocean ambient noise significantly.The correlation between the ocean ambient noise and the wind speed during the typhoon is much better than that in the non-typhoon period in the same Beaufort scale.Analysis of the correlation between the 415 h ocean ambient noise measured data and wind speed shows that,when the frequency is greater than 300 Hz,the correlation coefficient between the ocean ambient noise and the wind speed is greater than 0.5,achieving a moderate correlation;when the frequency is greater than 630 Hz,the correlation coefficient is between 0.8 and 0.9,achieving a high degree of correlation.The correlation between the ocean ambient noise and the wind speed is better than that between the ocean ambient noise and the significant wave height when the frequency is greater than 300 Hz.The correlation between the ocean ambient noise and the wind speed in infrasonic band from 10 Hz to 20 Hz is poor in the South China Sea,because the shipping is busy in this sea area and the ocean ambient noise is contaminated by the ship noise even during the typhoon.
基金supported by the National Natural Science Foundation of China(11304342)
文摘The effect of the correlation function of noise sources derived from the ocean wave spectrum on the vertical spatial correlation of ocean ambient noise is investigated. The spatial correlation models of ocean ambient noise usually assume that the surface noise sources are uncorrelated. This assumption can be used to explain some physical phenomena, but it is not consistent with the real situation. Considering the relation between the ocean wave motion and the ambient noise generated by wind, the spectrum of ocean wave is introduced to calculate the vertical correlation of ocean ambient noise as the correlation function of noise sources by using the Kuperman-Ingenito （K/I） noise model. The comparison of the simulations and the experimental data shows that the simulations of vertical correlation of ambient noise have some differences with the experimental data by assuming the noise sources are uncorrelated and the simulations of vertical correlation of ambient noise have a good agreement with the experimental data by using the correlation function of noise sources derived from the ocean wave spectrum under the situation of high wind speed.
文摘Physiological and behavioral systems exist to reduce the stress that the intertidal fauna may face during the unsuitable tidal phase. Cerithidea decollata is a common western Indian Ocean mangrove gastropod. It feeds on the ground at low tide, and climbs the trees two-three hours before the water arrival to avoid submersion. Moreover, it regularly settles on the trunk roughly 40 centimeters above the level that the water will reach, in spite of the irregular East African tidal pattern. Migration usually takes place about twice a day unless at Neap Tide, when snails may remain on the dry ground. Biological clock cannot account for water level foreseeing while direct visual cues or chemical information from the water itself or from previous migrations have already been experimentally discarded. Indirect cues could be hypothesize related to the effect of the oceanic wave reaching the coast and the barrier reef (seismic noise), or alternatively related to changes in ground resistivity (self potential) caused by the sea water moving close. To verify these hypotheses a seismic noise and self potential survey was carried out at Mida Creek (Kenya). This paper presents the first results of the seismic noise measurements. A significant correlation between the time evolution (mean value) of the low frequency seismic signal, tides, and snails movements has been identified.
文摘通过对噪声测量潜标系统测得的94 d海洋环境噪声数据及相应的气象数据进行联合时频、相关性、统计特性分析,得到试验海区风速、降雨等自然现象与噪声谱级之间的关系。分析结果表明,海洋环境噪声谱级与风速变化在低频段相关性较低,高频段相关性较高,同时1 k Hz以上频段谱级值分布接近呈正态分布;降雨对环境噪声的影响主要分布在500 Hz以上频段。
