Reduction in the dynamical complexity of the ocean ambient noise in the presence of target

Abstract

In this paper, we intend to quantify the dynamical complexity ofunderwater acoustical signals (UAS) based on multiscale sample entropy (MSE). MSE is calculated for three types of UAS which were measured in the South China Sea: ambient noise, and near and distant experimental vessels moving at constant velocity. [The analysis of real UAS exhibit high entropy values were assigned for ambient noise and low values for target signals.][NOTE: it is not clear what this means] This result suggests that the ambient noise is dynamically more complex than the target signals within the ambient noise. [It is also shown that dynamical behavior of far target approaching ambient noise behavior due to the weak ship noise.][NOTE: it is not clear what this means] This affirms that ship noise is regular and, when present in ambient noise, can be detected by the change in their dynamical complexity.