The sound-speed gradient and refraction in the near-ground atmosphere

2003 ◽  
Vol 113 (2) ◽  
pp. 750-757 ◽  
Author(s):  
D. Keith Wilson
Keyword(s):  
Sound Speed ◽  
Speed Gradient

Broadband Geoacoustic Deduction

1998 ◽  
Vol 06 (01n02) ◽  
pp. 45-59 ◽  
Author(s):  
R. M. Hamson ◽  
M. A. Ainslie
Keyword(s):  
Sound Speed ◽  
Test Cases ◽  
Data Sets ◽  
Sediment Layer ◽  
Frequency Data ◽  
Transmission Losses ◽  
Vertical Array ◽  
Starting Point ◽  
Versus Range ◽  
Speed Gradient

A two-stage approach to the geoacoustic inversion problems of selected Workshop '97 test cases is described. Initial parameters are deduced by inspection of transmission losses versus range, depth and frequency, and comparison with the calibration case. These provide a starting point for a conventional matched-field inversion applied to individual frequency data sets for a vertical array at 5-km range using the normal mode model SUPERSNAP and the standard Bartlett processor. Grid searches are carried out over pairs of parameters using: 500-Hz data to establish the sediment density and top sediment sound speed, 100-Hz data to estimate the sound speed gradient in the sediment layer and 25-Hz data for the remaining parameters. Results and error bounds are presented for two realizations of the SD workshop case. Partial results are presented for the SO case. Issues regarding SUPERSNAP/SAFARI mismatches are also discussed.

scholarly journals A three-dimensional bistatic reverberation model of underwater explosion by interface scattering at variable sound speeds

2018 ◽  
Vol 38 (2) ◽  
pp. 427-440
Author(s):  
Guo Rui ◽  
Lei Liu ◽  
Sheng Zhen-Xin ◽  
Song Pu
Keyword(s):  
High Intensity ◽  
Sound Speed ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Interference Effects ◽  
High Intensity Zone ◽  
Interface Scattering ◽  
Proposed Model ◽  
Lower Magnitude ◽  
Speed Gradient

Underwater reverberation is a main limitation of the sonar performance and thereby the reverberation level estimation becomes crucial. In this study, based on the Lambert law and ray theory, a model for predicting 3D bistatic reverberation performance by interface scattering at linear sound speed profile is established and then verified through the underwater explosion experiments. The Influences of source and receiver positions, and relative sound speed gradient on reverberation performance are further investigated. The results indicate that: (1) the proposed model can predict the short-range mean reverberation level effectively, with the deviation 2–4 dB and describe the whole reverberation level distribution in some details; (2) at the early reverberation phase, the interference effects between the interface scattering sounds are considerable and a dominating interface exists; the counterbalance between the losses by scattering, spreading and medium absorption results in the local high-intensity zones close to corresponding interfaces, respectively; (3) as the sound source moves towards some interface, associated local high-intensity zone gradually expands, while the other one shrinks; if the sound speed approaches are constant, an extra local high-intensity zone will appear between the previous two but with a lower magnitude.

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