Validity of the sonar equation and Babinet's principle for scattering in a stratified medium.

摘要: The sonar equation rests on the assumption that received sound pressure level after scattering can be written in decibels as a sum of four terms: source level, transmission loss from to target, target strength, and receiver. This is generally not valid for shallow water waveguide lead large errors inconsistencies estimating target’s properties well its limiting range detection. By application coherent theory, found become approximately when object’s complex scatter function roughly constant over equivalent horizontal grazing angles ±Δψ spanned by dominant modes. true (1) all objects spatial extent L wavelength λ 2Δψ<λ/2L (2) spheres certain other rounded nonforward azimuths, even does hold. may made lowering active frequency operation waveguide. often desirable because it greatly simplifies analysis necessary classification localization. Similarly, conditions are given Babinet’s principle becomes