Attenuation in marine sediments: In situ measurements versus propagation‐loss inversions.

Abstract

Acoustic attenuation in marine sediments may be measured either in situ, from the difference in signal level at two embedded probes, or from an inversion of transmission loss in the water column. Most in situ measurements are performed above 10 kHz and return an attenuation that scales as the first power of frequency, whereas transmission‐loss inversions are performed at lower frequencies, returning a near‐square‐law variation with frequency. The difference between the in situ and transmission‐loss estimates could be due to a combination of factors, including bottom roughness, which may lead to an enhanced attenuation from the transmission‐loss inversions. The nonoverlapping frequency bands of the two techniques could also account for the differences in the estimated scalings of attenuation with frequency. Thus, the attenuation could scale roughly as the square of the frequency below a few kilohertz, transitioning to a linear dependence above 10 kHz. Such behavior would be consistent with the recently dev...