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Pulse propagation in the surface duct with the source far below the duct is analyzed. Experimental results show that through the duct, the sound can propagate to the range much farther than that predicted by the ray theory. Besides, the propagation range is strongly related with the signal frequency. This propagation path is reproduced using the normal mode model. Furthermore, the ray representation...
This paper addresses the problem of automatic learning of statistical models of clicks for odontocete species classifications, particularly focusing on improving accuracy of the classifier by iteratively identifying click-like sounds that are likely to be noise and removing these from the model training set. The algorithm is weakly supervised in that no hand-labeled click regions are available, but...
Performance of an underwater acoustic communication is affected by the characteristics of the underwater channel. Especially, an important feature of the underwater channel is the multipath propagation caused by the surface and bottom reflections. These interference effects lead to the Inter-Symbol-Interference. To determine the transmitted data at the receiver, the receiver needs the channel estimator...
Study results derived from global tide gauge data indicate that the global waters were simultaneously subject to the modulation of lunar nodal tide showing a period of 18.6 years and rose at a rate of about 2 mm per year in the past century. In contrast to other regions, those sitting along the east Atlantic Ocean coastal lines show strong semi-diurnal pattern and seemly do not suffer from extraordinary...
T waves excited by earthquakes propagate along the SOFAR channel with low transmission loss, and therefore can be recorded on land-based seismic stations and hydrophones located thousands of kilometers away from earthquake epicenters. Early T-wave observations are mostly based on recordings by land-based stations due to the mechanics of the energy conversion of acoustic waves into seismic phases....
In the shallow water environment, detecting and classifying buried objects is a challenging problem with high operational importance. Acoustical wave becomes an important tool in the detection of objects in underwater systems due to its effectiveness of propagation in the water. Later on, the acoustic scattered field modal for fluid-loaded and thin spherical shell have been determined by the shell's...
Detecting underwater objects is an important application in marine applications. Most of the techniques are based on the amplitude related techniques, whereby the amplitude of the received echo is used to detect objects within specified bounds. Amplitude techniques however are prone to interference and attenuation, thus limiting the capabilities of such systems. Hence, the aim of this paper is to...
This paper introduces a stochastic approach that considers the distributed classification problem for a network of underwater acoustic sensors. The proposed classifier applies the third order polynomial regression to the instantaneous frequency extracted from time-frequency representation of different classes of signals and represent the polynomial's coefficients in a three-dimensional representation...
This paper addresses the problem of underwater acoustic signal denoising. This field has been mainly investigated as it allows signal-to-noise ratio enhancement, a prerequisite to any data interpretation. Underwater acoustic signal denoising shares similarities with speech signal processing since both deals with acoustic signals, consequently it is possible under some manipulations to use speech processing...
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