Abstract Underwater acoustics signal is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water and its boundaries The water may be in the dam ocean a lake or a tank There are some frequencies affiliated with underwater acoustics are between 10 Hz and 1 MHz There are some major steps for underwater signal de noising The first step deals with signal preprocessing which including amplifying filtering and take use of analogy digital AD technique to save signals as digital file The underwater acoustic signal is affected by ocean interference and ambient noise disturbance during its propagation in ocean Acoustic waves are the most important characteristic to convey data in underwater domain as a practical method But the oceans are increasingly exposed to sounds from human activities such as shipping and the building of foundations for offshore construction projects and other different noise Keyword underwater acoustic signal wavelet transform signal processing denoising noise reduction
1 Introduction Because of the activities of people in the ocean are expanded the field of underwater acoustics has been extensively developed in a variety of applications including acoustic communication the detection and location of surface and subsurface objects depth sounders and sub bottom profiling for seismic exploration l underwater acoustic signals that received from ocean are the signal of ships radiated when it sails on the ocean The aim of this paper is to develop a de noising system and evaluate the effect of wavelet de noising processing for underwater acoustic signals Noise hampers sonar data collection and related processing of the data to extract information since many of the signals of interest are of short duration and of relatively low energy Underwater signal transmission is a challenging task since the usable frequency range is limited to low frequency and the transmission of electromagnetic waves is impossible due to its high attenuation nature The types of attenuation that affects the sound signal are transmission loss Spreading Loss Attenuation Loss Background noise like Self Noise Machinery Noise Flow Noise etc 1 1 Motivation Human interaction is the study in underwater acoustic signal which is the rapidly growing topic everywhere Communication purpose Commercial Warship Acoustic communications form an active field of research with significant challenges to overcome especially in horizontal shallow water channels 1 2 Objective Reduce noise in underwater for acoustic signal Sound propagation losses Self noise and ambient noise SNR Mixed Gaussian noise
Underwater noise has been divided into two main types Impulsive Loud intermittent or infrequent noises such as those generated by piling and seismic surveys Continuous Lower level constant noises such as those generated by shipping and wind turbines These two types of MSFD related noise have different impacts on marine life In addition mid frequency naval sonar may be harmful to marine mammals The frequency or pitch of the noise is also important as animals are sensitive to different frequencies
5 The underwater acoustic signal is affected by ocean interference and ambient noise disturbance during its propagation in ocean Therefore the signal reveal random process and time varying characteristics The procedure consists of three parts First wavelet transformation of the underwater acoustic signals Secondly threshold of wavelet coefficients Thirdly inverse wavelet transformation of reconstructing modified signals 6 Because of the activities of people in the ocean are expanded the field of underwater acoustics has been extensively developed in a variety of applications including acoustic communication the detection and location of surface and subsurface objects depth sounders and sub bottom profiling for seismic exploration 7 The Ultrasonic signal is most commonly used for the depth estimation This signal is affected by various underwater noises which results in inaccurate depth estimation The objective of this paper is to provide noise reduction methods for underwater acoustic signal In present work the signal processing is done on the data collected using TC2122 dual frequency transducer along with the Navy sound 415 echo sounder There are two signal processing techniques which are used The first method is denoising algorithm based on Stationary wavelet transform SWT
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