Using analytic models and simulation results, we examine spatial reuse and the effectiveness of RTS/CTS MAC protocols in underwater acoustic networks. We are not looking at the question of network throughput, which is affected mostly by propagation delay, but rather the protocol’s ability to prevent collisions. RTS/CTS-based collision-avoidance protocols require successful detection of the hand...

Using acoustic sensors for detecting, localizing and classi@ng noise sources of any kind and in particular related to potentially adverse activities is an already well established technique applied in underwater activities. It now appears also as a significant multiplier for airborne automatic detection and localization of warning sounds such as: blasts, gunshots or shouts in public buildings s...

Underwater acoustic channels are recognized for being one of the most difficult propagation media due to considerable difficulties such as: multipath, ambient noise, time-frequency selective fading. The exploitation of sparsity contained in underwater acoustic channels provides a potential solution to improve the performance of underwater acoustic channel estimation. Compared with the classic l...

— Snapping shrimp dominate the high frequency soundscape in the warm shallow waters around Singapore. The noises produced by these small creatures are a result of the collapse of cavitation bubbles they produce. During the rapid collapse, the temperatures in the bubble can momentarily reach the surface temperature of the sun, and produce impulsive noise with source levels higher than 190 dB re ...

In recent years, underwater acoustic wireless sensor networks have been used in many areas. There have been many field trials of acoustic propagation models and statistics for shallow water conditions. However, field trials are limited environmentally and, hence, not widely accepted. Simulations of the impulse response of a shallow underwater acoustic channel allows less expensive system tests ...

Snapping shrimp noise is thought to be a major component of ambient noise at high frequencies (2 kHz 300 kHz) in warm shallow water. We have designed an experiment to investigate its temporal and spatial distribution and variability. This information has application to many underwater acoustic systems in providing background knowledge about the structure of this class of noise. The experiment r...

Practical application of underwater target echo signal usually get disturbed a Gaussian noise and non-Gaussian noise, in view of the signal recognition problem, this paper proposes a double spectrum analysis based on wavelet transform domain method of weak signal and D-S data fusion algorithm. Through the study of double spectrum of the wavelet transform domain analysis to the signal processing...

Image filtering algorithms are applied on images to remove the different types of noise that are either present in the image during capturing or injected in to the image during transmission. Underwater images when captured usually have Gaussian noise, speckle noise and salt and pepper noise. In this work, five different image filtering algorithms are compared for the three different noise types...