Propagation and reverberation implications of seabed dispersion

Abstract

The significance of the seabed geoacoustic properties to shallow water acoustic propagation is well established, and consequently the dispersion, or frequency dependence of the sound speed and the attenuation may be significant to the performance of broadband acoustic systems, whether for acoustic sensing or for communication. On the other hand, it is equally well established that the seabed significance is highly dependent on the system configuration, e.g., source and receiver depths, and the same will therefore obviously be the case for the dispersion. This paper will review the propagation effects of frequency dependent seabed geoacoustics, under characteristic seasonal environmental conditions, and typical system configurations. The associated implications to the acoustic system performance will be discussed in the context of theoretical performance bounds, such as the Cramer-Rao lower bounds, using established wave theory propagation models for range-independent and -dependent environments. Among the specific examples will be the effect of strong sediment dispersion in sandy sediments on buried target detection by low-frequency SAS systems operating in the 1–10 kHz regime, and broadband acoustic communication systems, including the effect of dispersion on seabed reverberation. [Work supported by ONR.]