Entry Date:
December 2, 2001

Statistical Theory of Ocean-Acoustic Measurements

Principal Investigator Nicholas Makris

Natural disturbances, such as underwater turbulence and passing surface or internal waves, cause the ocean-acoustic medium to be in such a state of flux that a signal, deterministic when transmitted from its source, becomes randomized by the time it reaches a receiver that is only several water-column distances away. When not properly accounted for, such randomization can severely degrade the accuracy of an experimental measurement, as well as any parameter estimates based upon that measurement. Professor Makris has merged concepts of temporal-coherence theory and information theory to describe ocean-acoustic intensity measurements when the signals are completely randomized. This initial work, done while he was at NRLI has been generalized at MIT to include the case where a deterministic component also survives the propagation, along with the otherwise randomized signal. Some primary results include general forms for the standard deviation and bias of estimates made with sonar equations. This is significant because the sonar equation is one of the primary analytic tools available to researchers in underwater acoustics.