Geoacoustic inversion by mode amplitude perturbation

Abstract

This paper introduces a perturbative inversion algorithm for determining sea floor acoustic properties, which uses modal amplitudes as input data. Perturbative inverse methods have been used in the past to estimate bottom acoustic properties in sediments, but up to this point these methods have used only the modal eigenvalues as input data. As with previous perturbative inversion methods, the one developed in this paper solves the nonlinear inverse problem using a series of approximate, linear steps. Examples of the method applied to synthetic and experimental data are provided to demonstrate the method's feasibility. Finally, it is shown that modal eigenvalue and amplitude perturbation can be combined into a single inversion algorithm that uses all of the potentially available modal data.

Inversion of ocean environmental variations via time-reversal acoustics

“…they are evaluated via the SSP measurement or directly measured. Recent research shows that the mode functions can also be estimated via SSP perturbation [34], which will be investigated in future work.…”

“…, Q, using a priori geoacoustic parameters. These geoacoustic parameters can also be inverted combined with w by equation (34). (iii) Calculate φ (2) n (z sq ), n = 1, 2, .…”

“…. , Q, with the SSP at the PS location (by a measurement made at the PS) or invert both φ (2) n (z sq ) and w by equation (34). (iv) Measure the focusing signals ptr and invert w by equation (34).…”

“…, Q, with the SSP at the PS location (by a measurement made at the PS) or invert both φ (2) n (z sq ) and w by equation (34). (iv) Measure the focusing signals ptr and invert w by equation (34). (v) Estimate the variation of the SSP along the range between the PS transmission and the SRA retransmission by equation (36).…”

“…Full-wave synthetic pressure fields were generated using the coupled normal mode code [33]. Figure 9 plots J 1 ( w1 ) as a function of w1 /r s , where J 1 ( w1 ) is evaluated by equation (34). Figure 9 shows that the estimated value is very close to the true one for the SNR greater than 0 dB.…”