International Journal of Computer Engineering and Sciences (IJCES) Vol. 1, Issue 7, July-2015, Available at: www.knowledgecuddle.com/index.php/IJCES 1 eISSN: -2394-6180 A Literature Survey on Ambient Noise Analysis For underwater Acoustic Signals Sauda Sadaf, Yashaswini P. 1 , Soumya Halagur 2 , Fazil Khan 3 , Dr. Shanta Rangaswamy 4 1234 Department of Computer Science and Engineering R.V. College of Engineering, Bangalore-560060 Abstract- Transmitting data with water as the medium is called underwater communication. Electromagnetic signals are better attenuated in water than sound. Hence it is the most reliable and versatile means of communication underwater. The acoustic signals will be affected by ocean driven noise during transmission. Ambient noise is the background noise which has to be subtracted from the acoustic signal for smooth transmission. Hence the recognition and reduction of ambient noise is the essential part of underwater signal transmission. Studies and research are being carried out extensively in this area. There are many works reported and the research is still in progress. This literature survey presents the work done on the research front of ambient noise affecting acoustic signals. Key Words: - Underwater communication, Ambient noise, SNR, MSE, Noise Reduction, Signal. I. INTRODUCTION Transmitting data considering underwater as the medium is called underwater communication. Acoustic wave is the best suitable optimum medium for signal transmission in ocean, because the electromagnetic waves scatter due to the high frequency [1]. Acoustic signal transmission is the most versatile and also widely used technique for transmission in underwater environments due to the low attenuation of sound in water; especially in thermally stable and deep water settings. Underwater acoustics signals are affected by ambient noise during transmission. Hence, identification and also recognition for acoustic signals is the essential part of underwater technologies. Transmitting signal under ocean considering water as a channel is a challenge because of the effect of spreading, reverberation, attenuation and absorption adding to contribution due to ambient noises. Ambient noises in ocean can be classified into two types: 1. Man made (Shipping, motor on boat, aircraft over the ocean.) 2. Natural noise (Rain, seismic, wind and marine animals.). Ambient noises have more effect towards reducing the acoustic signal quality. Sound received by an Omni-directional sensor which is not from the sensor itself or the manner in which it is mounted is called ambient noise [2]. It is the background noise in the sea from either natural or man-made sources, and may be divided into 4 categories: hydrodynamic, seismic, ocean traffic and biological [11][12]. o Hydrodynamic Noise: It is caused by the movement of water itself because of tides, winds, currents and storms. Level of hydrodynamic noise present in sea is directly related to the condition of the surface of sea. When the surface is agitated by wind or storm, the noise level increases which reduces the capability of detection. Very high hydrodynamic noise levels which are caused by storms in the general area of the ship may result in complete loss of all reception of signal.