Effects of source distribution in depth on ocean ambient noise field

2012 ◽  
Author(s):  
Jianheng Lin ◽  
Pengfei Jiang ◽  
Baoyou Yin ◽  
JiaLiang Li ◽  
Li Ma
Keyword(s):  
Ambient Noise ◽  
Source Distribution ◽  
Noise Field

A Method for Noise Source Levels Inversion with Underwater Ambient Noise Generated by Typhoon in Deep Ocean

2018 ◽  
Vol 26 (02) ◽  
pp. 1850007 ◽  
Author(s):  
Qiulong Yang ◽  
Kunde Yang ◽  
Shunli Duan
Keyword(s):  
Ambient Noise ◽  
Noise Source ◽  
Surface Wind ◽  
Deep Ocean ◽  
Noise Sources ◽  
Noise Field ◽  
Sea Surface Wind ◽  
Source Level ◽  
The Western Pacific ◽  
Good Agreement

Sea-surface wind agitation can be considered the dominant noise sources whose intensity relies on local wind speed during typhoon period. Noise source levels in previous researches may be unappreciated for all oceanic regions and should be corrected for modeling typhoon-generated ambient noise fields in deep ocean. This work describes the inversion of wind-driven noise source level based on a noise field model and experimental measurements, and the verification of the inverted noise source levels with experimental results during typhoon period. A method based on ray approach is presented for modeling underwater ambient noise fields generated by typhoons in deep ocean. Besides, acoustic field reciprocity is utilized to decrease the calculation amount in modeling ambient noise field. What is more, the depth dependence and the vertical directionality of noise field based on the modeling method and the Holland typhoon model are evaluated and analyzed in deep ocean. Furthermore, typhoons named “Soulik” in 2013 and “Nida” in 2016 passed by the receivers deployed in the western Pacific (WP) and the South China Sea (SCS). Variations in sound speed profile, bathymetry, and the related oceanic meteorological parameters are analyzed and taken into consideration for modeling noise field. Boundary constraint simulated annealing (SA) method is utilized to invert the three parameters of noise source levels and to minimize the objective function value. The prediction results with the inverted noise source levels exhibit good agreement with the measured experiment data and are compared with predicted results with other noise sources levels derived in previous researches.

scholarly journals Ambient noise field and propagation in an Arctic fjord Kongsfjorden, Svalbard

Polar Science ◽  
2018 ◽  
Vol 17 ◽  
pp. 40-49 ◽  
Author(s):  
M.C. Sanjana ◽  
G. Latha ◽  
A. Thirunavukkarasu ◽  
R. Venkatesan
Keyword(s):  
Ambient Noise ◽  
Noise Field ◽  
Arctic Fjord

The effect of monomolecular films on the underlying ocean ambient noise field

1988 ◽  
Vol 84 (S1) ◽  
pp. S122-S122
Author(s):  
Jim Rohr ◽  
Ray Glass ◽  
Brett D. Castile
Keyword(s):  
Ambient Noise ◽  
Noise Field ◽  
Monomolecular Films

Source-structure trade-offs in noise correlation functions in 3-D

2020 ◽  
Author(s):  
Korbinian Sager ◽  
Christian Boehm ◽  
Victor Tsai
Keyword(s):  
Correlation Functions ◽  
Ambient Noise ◽  
Hessian Matrix ◽  
Seismic Wave Propagation ◽  
Source Distribution ◽  
Earth Structure ◽  
Noise Correlation ◽  
Noise Sources ◽  
Trade Offs ◽  
Source Structure

<p>Noise correlation functions are shaped by both noise sources and Earth structure. The extraction of information is thus inevitably affected by source-structure trade-offs. Resorting to the principle of Green’s function retrieval deceptively renders the distribution of ambient noise sources unimportant and existing trade-offs are typically ignored. In our approach, we consider correlation functions as self-consistent observables. We account for arbitrary noise source distributions in both space and frequency, and for the complete seismic wave propagation physics in 3-D heterogeneous and attenuating media. We are therefore not only able to minimize the detrimental effect of a wrong (homogeneous) source distribution on 3D Earth structure by including it as an inversion parameter, but also to quantify underlying trade-offs.</p><p>The forward problem of modeling correlation functions and the computation of sensitivity kernels for noise sources and Earth structure are implemented based on the spectral-element solver Salvus. We extend the framework with the evaluation of second derivatives in terms of Hessian-vector products. In the context of probabilistic inverse problems, the inverse Hessian matrix in the vicinity of an optimal model with vanishing first derivatives and under the assumption of Gaussian statistics can be interpreted as an approximation of the posterior covariance matrix. The Hessian matrix therefore contains all the information on resolution and trade-offs that we are trying to retrieve. We investigate the geometry of trade-offs and the effect of the measurement type. In addition, since we only invert for sources at the surface of the Earth, we study how potential scatterers at depth are mapped into the inferred source distribution.</p><p>A profound understanding of the physics behind correlation functions and the quantification of trade-offs is essential for full waveform ambient noise inversion that aims to exploit waveform details for the benefit of improved resolution compared to traditional ambient noise tomography.</p>

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