Backscattered acoustic intensities are studied analytically for manganese nodule deposits excited by a normally incident plane wave. The primary objective is to use this remote-sensing technique to infer the nodule concentration as well as its size distribution from the frequency spectrum of the acoustic response.For sparse distributions of scatterers, multiple scattering theory has been used to obtain the coherent reflection and transmission coefficients from the sea floor covered with manganese nodules. The derived equations can also be used for densely distributed configurations when considering higher-order statistics between scatterers. The validity of the formalism is examined by using the principle of conservation of energy and considering both the coherent and the incoherent intensities.Numerical results of acoustic intensities are highly frequency-dependent, especially when the nondimensional frequency ka is greater than 1. The strength of the acoustic intensity is proportional to nodule concentration. Different size distributions of nodules can be distinguished through use of the intensity measurements. However only a minor difference is observed in the low-frequency range between uniform and Rayleigh size distributions.

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