The variability in shape and amplitude of bottom echoes affects the resolution of geoacoustic parameter estimation techniques that match measured bottom-echo envelopes with envelope models derived from incoherent acoustic backscatter theory at the sediment–water interface and in the sediment volume. Following earlier echo envelope matching work carried out with data collected at 10–100 kHz in San Diego Bay [Sternlicht and de Moustier, J. Acoust. Soc. Am. 105, 1206 (1999)], coarse- and fine-grain substrates are identified by estimates of their mean grain size (Mφ) and of the strength (w2) of their power-law roughness spectrum describing the spatial statistics of the interface. Statistics of the (Mφ, w2) estimates are combined with those from Monte Carlo simulations, based on the data covariance matrices, to demonstrate that in sandy substrates, echo variability has little effect on estimates of w2, and a pronounced effect on estimates of Mφ. The reverse pattern is observed for fine-grain substrates. However, the parameter estimation technique used introduces a degree of correlation between Mφ and w2, which is especially large for sand substrates. These observations are consistent with nature, where relief spectra of coarser sediments contain more energy than those of fine-grain substrates. [Work supported by ONR.]
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