Spectral analysis of bistatic scattering from underwater elastic cylinders and spheres

Abstract

Far field sound scattering from underwater elastic spheres and finite cylinders is considered over the full range of scattering angles. Three models for the frequency response of the scattered field are evaluated: a hybrid finite element/propagation simulation for a finite cylinder with broadside illumination, an approximate solution for the finite cylinder, and the exact solution for a sphere. The cylinder models are shown to give comparable results, attesting to the strength of the finite cylinder approximate solution. Interference and resonance structure present in the frequency response of the targets is identified and discussed, and the bistatic spectra for a variety of elastic sphere materials are presented. A thorough understanding of the complicated angle and frequency dependence of the scattering from simple elastic targets is helpful for interpretation of backscattering data from targets at or near an interface, or for scattering data taken by moving automated underwater vehicles, acoustic arrays, or other forms of data collection involving bistatic scattering.

Underwater Spherical Shell Classification and Parameter Estimation Based on Acoustic Backscattering Characteristics

“…Researchers have proved that the incident wave frequency c f with the maximum amplitude of the first 0 A  wave is related to the radius-thickness-ratio, which can be used to estimate the radius and thickness of the object, whereas it is difficult to obtain the c f in practical application. In response, Li proposed two approximate equations to evaluate the radius and thickness of a thin spherical shell [28] as shown in (8) and (9). .…”

“…In this section, we train the regression model based on CNN to estimate the radius and thickness of the object, and compare the performance to the baseline method [28]. The parameters in (8) and (9) need to satisfy two conditions:…”

“…With the improvement of calculation and experiment, it becomes possible to obtain the characteristics of scattered echoes under different incident angles of sound waves. By comparing the consistency between the experimental and calculated results in the time and the frequency domain, researchers used the time-angle spectrum and frequencyangle spectrum to analyze the scattering characteristics of the target [8]. Since the backscattered echo varies with the incident angle of the sound wave, different components appears under the condition of different incident angles, thereby the type of echo component can be identified according to the transformation law [9].…”

Rayleigh scattering of a cylindrical sound wave by an infinite cylinder

“…[1][2][3][4][5] However, knowledge of the full Green's functions is necessary for many problems of current interest for which the physical spacing between the scatterers themselves or the scatterers' separation from a source or boundary is comparable to their size. In underwater acoustics, such problems can arise in dense multi-scatterer configurations, 6 radiation by finite sources, [7][8][9][10] target classification, [11][12][13] source localization, 14 scattering suppression, 15,16 and when calculating the radiation and scattering of sound due to objects located near the ocean surface 17,18 or the seafloor. [19][20][21] No simple analytic solutions are readily available for such problems, and numerical methods have to be used.…”