LONG-TERM GOALS • To evaluate feasibility and determine physical limits of performance of a passive acoustic system for characterization of a time-varying ocean where ambient acoustic noise is utilized as a probing signal. • To develop a passive remote sensing technique for acoustic characterization of oceanic currents. OBJECTIVES 1. To demonstrate theoretically emergence of the deterministic G...

Automatic recognition of an acoustic signature in underwater environments is an important and active field with multiple applications, one of which is vessel recognition. When a vessel moves through the sea, its engine and the cavitation generated by its propellers produce an acoustic wave of unique characteristics that allow for its individual identification. The problem of identification invo...

Water is very effective at propagating sound waves and as a result there is significant concern that as ships increase in terms of size and effective power their impact on the underwater sound scape is causing real environmental harm (Tasker et al., 2010). While of course there are multiple sources of noise in the Oceans, natural and anthropogenic alike, shipping as a whole contributes to a lar...

Underwater acoustic orthogonal frequency division multiplexing (OFDM) enables simple frequency domain equalization, but its performance is often limited by intercarrier interference (ICI) that is induced by channel variation, in addition to the ambient noise. As the signal itself, the variance of the ICI is frequency dependent as (i) the transmitter often has a nonideal transmit voltage respons...

In recent years, underwater acoustic (UWA) communications have received much attention as their applications have begun to shift from military toward commercial. Digital communications through UWA channels differ substantially from those in other media, such as radio channels, due to severe signal degradations caused by multipath propagation and high temporal and spatial variability of the chan...

This paper describes a prediction method for the contribution of the main onboard machinery to the underwater acoustic signature of steel surface vessels that can be used during the design stage. There are two reasons for the development of this method. Firstly, a small acoustic signature is important for naval and research vessels, due to operational requirements concerning detection and inter...

Today, underwater acoustic communication is developing for its various applications. For signal transmission in underwater using ocean/ sea/lakes/rivers as a medium an appropriate underwater acoustic system is required. The significant characteristic of ocean makes the underwater communication difficult using electromagnetic waves. The characteristics of an acoustic signal make a good candidate...

An underwater robot is one of the important ocean equipment, and especially its stealth performance has influenced on the vitality in naval warfare. Structure radiation noise as the main source of underwater robot noise, so analysis on vibration and noise radiation is a topic of great concern. The way is used widely that based on fluid-solid coupling modal analysis combined with simulation on v...