Analysis and application of the acoustic interfered field distortion for acoustic forward-scattering detection of underwater targets

The signal to direct-blast ratio SDRF in acoustic forward-scattering detection can measure the relative magnitudes of the forward scattered wave and the direct-blast, but it does not consider the interference between the two waves. These two waves interfere together actually and are difficult to separate, so SDRF is difficult to apply in target detection and analysis directly. Based on the signal to direct-blast ratio and considering the interference effect of the forward scattered wave and the direct-blast, a new parameter called the acoustic interfered field distortion ∆FTL is developed, and the corresponding calculation formula is also deduced. Compared with SDRF, ∆FTL can be obtained directly from data, which has the advantage of not relying on prior information to a certain extent. Based on this formula and combined with data from the Qiandao Lake scaled-target detection experiment, (1) the acoustic wave is found to be spherical wave by estimating the geometric expansion loss coefficient, and the results are consistent with the simulation results of ray sound field model based on the measured hydrological parameters, (2) the relation between ∆FTL and the target crossing position is quantitatively confirmed, which proves the effectiveness of the ∆FTL formula, (3) a performance evaluation scheme independent of prior information is established for direct-blast suppression techniques and then applied to the adaptive direct wave suppression method. The influences from acoustic leakage and attitude-angle disturbance of the target on the results can be ignored. These results show that ∆FTL can effectively replace SDRF, providing theoretical references for conducting performance evaluations on the acoustic forward-scattering detection analysis or the direct-blast suppression effect. © 2021 Acta Acustica.