Effect of frequency dependence of complex sound speed on impulse response in littoral seas

2005 ◽  
Vol 117 (4) ◽  
pp. 2503-2503
Author(s):  
David Knobles
Keyword(s):  
Frequency Dependence ◽  
Impulse Response ◽  
Sound Speed ◽  
Complex Sound

Frequency dependence of sound speed and attenuation in marine sediments

2006 ◽  
Vol 120 (5) ◽  
pp. 3099-3099
Author(s):  
William M. Carey ◽  
Ji‐Xun Zhou ◽  
Allan D. Pierce
Keyword(s):  
Frequency Dependence ◽  
Marine Sediments ◽  
Sound Speed

3D numerical modeling of induced-polarization electromagnetic response based on the finite-difference time-domain method

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. E385-E398 ◽  
Author(s):  
Yanju Ji ◽  
Yanqi Wu ◽  
Shanshan Guan ◽  
Xuejiao Zhao
Keyword(s):  
Frequency Dependence ◽  
Impulse Response ◽  
Time Constant ◽  
Time Domain ◽  
Characteristic Time ◽  
Induced Polarization ◽  
Order System ◽  
Ohm’S Law ◽  
Ohm's Law ◽  
Cole Model

Induced-polarization (IP) effects have a significant influence on transient electromagnetic (TEM) data, which commonly manifest a reversed sign. Polarization media usually have a very high economic value. To study the IP effects, a new method for modeling the time-domain electromagnetic signals of 3D dispersive materials is developed. Due to the fractional time derivatives, two main difficulties are needed to be conquered: the derivation of Cole-Cole model impulse response function and the discrete recursion of convolution in Ohm’s law. We use a frequency-domain rational approximation method and the linear programming technique to transfer the fractional order system into an integer order system. This method enables us to achieve a relatively simple and high-precision solution of the Cole-Cole model impulse response. A discrete recursion method for Ohm’s law convolution is proposed to realize an efficient numerical simulation of 3D polarization media by eliminating the prohibitive computing demands. Comparisons with published methods demonstrate the accuracy and efficiency of our algorithm. The characteristic time constant and chargeability have monotonic influences on the IP effects, whereas the frequency dependence indicates a nonmonotonic influence on the IP effects. The negative response is more significant when the frequency dependence is in the midrange. For a 3D low-resistivity chargeable body, a larger size reduces the decay rate of the induced field, which contributes to the obscuration of the polarization field. The middle-sized chargeable body can be detected under certain conditions: high chargeability, millisecond characteristic time constant, and middle frequency dependence. Small-sized chargeable bodies cannot be recognized at all by using the current forward-modeling method and instrument, which highlights the significance of precision improvement.

Computing Where Perturbations Affect the Acoustic Impulse Response in the Ocean

2018 ◽  
Vol 26 (02) ◽  
pp. 1850004
Author(s):  
John L. Spiesberger ◽  
Dmitry Yu Mikhin
Keyword(s):  
Wave Equation ◽  
Acoustic Wave ◽  
Impulse Response ◽  
Sound Speed ◽  
Acoustic Signals ◽  
Technological Advance ◽  
Propagation Model ◽  
Acoustic Wave Equation ◽  
Finite Frequency ◽  
The One

We compute accurate maps of oceanic perturbations affecting transient acoustic signals propagating from source to receiver. The technological advance involves coupling the one-way wave equation (OWWE) propagation model with the theory for the Differential Measure of Influence (DMI) yielding the map. The DMI requires two finite-frequency solutions of the acoustic wave equation obeying reciprocity: from source to receiver and vice versa. OWWE satisfies reciprocity at basin-scales with sound speed varying horizontally and vertically. At infinite frequency, maps of the DMI collapse into rays. Mapping the DMI is useful for understanding measurements of acoustic perturbations at finite frequencies.

Frequency dependence of sound speed and attenuation in fine-grained sediments from 25 to 250 kHz based on a probe method

2018 ◽  
Vol 160 ◽  
pp. 45-53 ◽  
Author(s):  
Jingqiang Wang ◽  
Baohua Liu ◽  
Guangming Kan ◽  
Guanbao Li ◽  
Jiewen Zheng ◽  
...  
Keyword(s):  
Frequency Dependence ◽  
Sound Speed ◽  
Probe Method ◽  
Fine Grained

scholarly journals On the technique of the inversion of helioseismological data

1988 ◽  
Vol 123 ◽  
pp. 137-140
Author(s):  
M.A. Brodsky ◽  
S. V. Vorontsov
Keyword(s):  
Phase Shift ◽  
Frequency Dependence ◽  
Sound Speed ◽  
Numerical Results ◽  
Speed Profile ◽  
Sound Speed Profile ◽  
Inversion Technique ◽  
Independent Determination ◽  
Effective Phase

The asymptotic inversion technique is developed, including independent determination of the sound speed profile and frequency dependence of the effective phase shift. Numerical results are presented.

High frequency dependence of sound speed and attenuation in coral sand sediments

2021 ◽  
Vol 234 ◽  
pp. 109215
Author(s):  
Jingqiang Wang ◽  
Guanbao Li ◽  
Guangming Kan ◽  
Zhengyu Hou ◽  
Xiangmei Meng ◽  
...  
Keyword(s):  
Frequency Dependence ◽  
High Frequency ◽  
Sound Speed ◽  
Coral Sand ◽  
Sand Sediments
Sign in / Sign up

Export Citation Format

Share Document