This study evaluates the impact of underwater ambient noise using seven real noise samples; Dolphin, Rain, Ferry, Sonar, Bubbles, Lightning, and Outboard Motor in three frequency ranges in extremely low frequency (ELF) band. The ELF band is the most significant bandwidth for underwater long-range communication. ELF band which is extended from 3 to 3000 Hz clearly, faces bandwidth limitation. Me...

in this paper, for the purpose of investigating horizontal sound propagation, based on the results obtained from practical measurements in the strait of hormoz and available data on sound speed variations at different depths, a comprehensive model for shallow water multipath underwater acoustic channel is presented. mathematical modeling of multipath effect is based on ray theory and the image ...

the mixture of natural and artificial seismic sources with random distributions cause diffuse wave field with random amplitudes and phases called noise. when noise is analyzed in a long-term process, it contains surface waves which are spread in all directions. thus, ambient noise contains data relevant to the surface waves. in recent years, as broadband seismic networks have been distributed v...

INTRODUCTION Signal transmission underwater is a challenging task. Generally, low frequency acoustic signals are used for transmission underwater as electromagnetic signals are highly attenuated. Any modulated signal transmitted in water, undergoes various losses due to attenuation, reverberation, spreading and internal waves etc apart from ambient noise due to natural and manmade sources. The ...

Predicting underwater detection capabilities as well as vulnerabilities depends strongly on the characteristics of the ocean acoustic propagation channel. Operational advantages can be obtained by exploiting the ambient noise field to characterize the channel. The long term goal of this research is to determine methods that take advantage of the ambient noise field to extract useful information...

This paper considers extrapolation of the vertical coherence of surface-generated oceanic ambient noise to simulate measurements made on a longer sensor array. The extrapolation method consists of projecting the noise coherence measured with a limited aperture array into the domain spanned by prolate spheroidal wave functions, which are an orthogonal basis defined by array parameters and the no...

The main focus of this paper is denoising of underwater acoustic signal to improve the performance of underwater acoustic instruments. The major sources of underwater ambient noises are distant shipping, wind, rain and biological activities. In this paper we have considered wind driven noise, which occupies wide bandwidth,as ambient noise source. A lot of research work has been done on denoisin...