Vertical Correlation of the Acoustic Field in Deep Water Measured with Explosive Sources

Li, Hui; Yang, Kunde; Lei, Zhixiong; Duan, Rui

doi:10.1007/s40857-017-0117-4

Cited by 5 publications

(5 citation statements)

References 20 publications

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“…It can be seen that the horizontal coefficient oscillates with range and horizontal separation, consistent with the findings of previous studies. [18,19] The sound field in the direct zone is strongly correlated and the HCR is greater than 1 km. The direct zone appears at the edge of the eddy, so the effect of eddies on the HCR in the direct zone is very weak.…”

Section: Horizontal Coherencementioning

confidence: 99%

Effects of mesoscale eddies on the spatial coherence of a middle range sound field in deep water

Gao¹,

Xu²,

Li³

2022

Chinese Phys. B

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The mesoscale eddies have a remarkable influence on the sound field underwater, and many previous studies investigate the effects of eddies on transmission loss (TL), convergence zone, time delay, etc. However, the effects of eddies on spatial coherence are less studied and remain unclear. In this paper, the effects of eddies on spatial coherence at the subsurface in deep water is investigated. The eddy environments are simulated with Gaussian eddy equations, the complex pressure field is obtained using a range dependent parabolic equation (PE) model, and the associated mechanism is analyzed based on ray theories and models. The results show that the cold/warm mesoscale eddies affect the spatial coherence in high intensity zone, by changing the locations and width of the convergence zone. In the shadow zone, the horizontal correlation radius (HCR) and the vertical correlation radius (VCR) increases with range and decreases with depth, and they are increased by warm eddies and decreased by cold eddies, mainly caused by variation of multipath structure.

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Section: Horizontal Coherencementioning

confidence: 99%

Effects of mesoscale eddies on the spatial coherence of a middle range sound field in deep water

Gao¹,

Xu²,

Li³

2022

Chinese Phys. B

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“…The vertical correlation coefficient describes the similarity of the signal received at the same horizontal range but different depths. It is a critical factor which greatly affected the AG [19]. The vertical correlation coefficient in the time domain can be expressed as…”

Section: Vertical Correlation Coefficientmentioning

confidence: 99%

Vertical Correlation and Array Gain Analysis for Vertical Line Array in Deep Water

et al. 2020

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Array gain (AG) is significant in evaluating the detection performance of the vertical line array, which is directly determined by the correlation of signal and noise, respectively. In this paper, we analyze the vertical correlation for a 16-element vertical line array experimented in the deep ocean in 2016. The ray interference theory is utilized to interpret the mechanism of the vertical correlation of the sound field in different zones. In the direct-arrival zone, the direct rays and once-surface-reflected rays are two dominated components, whose arrival time difference for each element are nearly the same, and the vertical correlation is high. In the shadow zone, the sound field is mainly dominated by bottom-reflected rays and the vertical correlation decreases due to different grazing angles and arrival times of each ray. Different from the previous assumption of noise independence, the effect of noise correlation on the AG is analyzed through the measured marine environmental noise. Results indicate that the noise correlation coefficients in two zones are low but not 0. In the direct-arrival zone, AG is about 10 dB, very close to the ideal value of 10 log M . AG even exceeds it when NG is negative. Moreover, AG in the direct-arrival zone is higher than the one in the shadow zone.

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“…Hence, the SNR s of the received sound pressure in the RAP can be very high. Second, the RAP has good stability in the time/space/frequency domain [ 4 ], and the SSP fluctuations and surface scattering have little effect on its acoustic propagation. The major reason is that the D received in RAP has a relatively large grazing angle.…”

Section: The Direct-arrival Zone and The Reliable Acoustic Pathmentioning

confidence: 99%

“…It is worthwhile to note that the theoretical solution of the vertical correlation coefficient based on the ray model can also be used to interpret the decline. According to [ 4 ], the vertical correlation coefficient in the frequency domain can be written as:

where

and

are the complex spectra of the acoustic signals

and

, respectively. In addition, ω 1 and ω 2 are the lower and upper angular frequencies of the filtered acoustic signals, respectively.…”

Section: Analysis Of the Signal Gain And Noise Gain Based On The Dmentioning

confidence: 99%

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Reliable Acoustic Path and Direct-Arrival Zone Spatial Gain Analysis for a Vertical Line Array

Qiu

Chen

et al. 2018

Sensors

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A method is developed in this paper to calculate the spatial gain of a vertical line array when the plane-wave assumption is not applicable and when the oceanic ambient noise is correlated. The proposed optimal array gain (OAG), which can evaluate the array’s performance and effectively guide its deployment, can be given by an equation in which the noise gain (NG) is subtracted from the signal gain (SG); hence, a high SG and a negative NG can enhance the performance of the array. OAGs and SGs with different array locations are simulated and analyzed based on the sound propagation properties of the direct-arrival zone (DAZ) and the reliable acoustic path (RAP) using ray theory. SG and NG are related to the correlation coefficients of the signals and noise, respectively, and the vertical correlation is determined by the structures of the multipath arrivals. The SG in the DAZ is always high because there is little difference between the multipath waves, while the SG in the RAP changes with the source-receiver range because of the variety of structure in the multiple arrivals. The SG under different conditions is simulated in this work. The “dual peak” structure can often be observed in the vertical directionality pattern of the noise because of the presence of bottom reflection and deep sound channel. When the directions of the signal and noise are close, the conventional beamformer will enhance the correlation of not only the signals but also the noise; thus, the directivity of the signals and noise are analyzed. Under the condition of having a typical sound speed profile, the OAG in some areas of the DAZ and RAP can achieve high values and even exceed the ideal gain of horizontal line array 10 logN dB, while, in some other areas, it will be lowered because of the influence of the NG. The proposed method of gain analysis can provide analysis methods for vertical arrays in the deep ocean under many conditions with references. The theory and simulation are tested by experimental data.

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Vertical Correlation of the Acoustic Field in Deep Water Measured with Explosive Sources

Cited by 5 publications

References 20 publications

Effects of mesoscale eddies on the spatial coherence of a middle range sound field in deep water

Effects of mesoscale eddies on the spatial coherence of a middle range sound field in deep water

Vertical Correlation and Array Gain Analysis for Vertical Line Array in Deep Water

Reliable Acoustic Path and Direct-Arrival Zone Spatial Gain Analysis for a Vertical Line Array

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