Wind dependence of ambient noise in shallow water of Arabian sea during pre-monsoon

Abstract

Underwater acoustics is a part of many marine projects. some scientists use sound to track ocean currents,identify potential obstacles,or quantify fish distributions.other part of research don't directly ise sound,but listen to ocean noise or investicate how marine animals produce and hear sounds.The noise level does not depend on the direction in which the wind is blowing. Waves do not break at lower wind speeds. Wind is one of the most important components of weather and climate. Winds are the primary driver of large-scale ocean currents. They are responsible for the formation of the Gulf Stream, for example. Improved understanding of the global pattern of wind is needed to improve weather and climate forecasting. Information on wind over the ocean helps meteorologists, oceanographers, and climatologists. Ambient noise data were collected for the period of six months in the shallow water of Arabian sea.Datas were collected for different wind speed ranges between 0.5 m/s to 7 m/s and the analysis were performed for frequencies ranging from 500 Hz to 7 KHz. The relative spectral energy distribution of sea noise is presented for a number of wind speeds .Linear relationship between the sea noise spectrum levels and the wind speed were found for the entire frequency range.

Topography and biological noise determine acoustic detectability on coral reefs

“…Snapping shrimps (Alpheus and Synalpheus), mantis shrimps (Stomatopoda), and occasionally larger crabs (Cancer and Portunus), triggerfishes and grazing fish and urchins are able to produce sound in a broad frequency range that includes 69kHz. Snapping shrimps, in particular, can be the dominant source of background noise in shallow tropical waters (Vijayabaskar and Rajendran 2010) and are found in coral reefs worldwide (Kennedy 2007). They are more active in darker periods like night and new moon, when they are less susceptible to predation (Radford et al 2008) producing noise 2-5 dB higher (Morisaka et al 2005).…”

Frequency Domain Based Approach for Denoising of Underwater Acoustic Signal Using EMD

“…The output of hydrophone is a voltage signal, which converts the acoustic pressure into voltage, based on the sensitivity of the hydrophone. The input signal also converted into sound pressure, that is measured in micropascal, which depends on the sensitivity of the hydrophone [10]. Proposed frequency domain thresholding approach worked well for different wind noises, i.e., noise collected for various wind speed.…”

Tropical littoral ambient noise probability density function model based on sea surface temperature

“…[3][4][5] SST is the most important factor controlling wind and hence surface waves. Various studies have been proposed representing a linear relationship between SST and thermally driven wind speed.…”

“…1 The site-specific spatio-temporal fluctuations of the ambient noise due to wind, wave, and currents, which are driven by the corresponding SST fluctuations in these regions, preclude the possibility of designing generalized mitigation strategies. [2][3][4][5][6][7][8][9][10][11][12] The SST determines the thermally driven wind and thus the ambient noise levels in the region, yet among the sea surface parameters, it is the least explored. [10][11][12] The wind driven ambient noise, manifest dominantly in the spectral band of 3-10 kHz, that has a direct impact on the mid-frequency sonar used for military and non-military applications like anti-submarine warfare (ASW) missions, fisheries, geological exploration, navigation, and surveillance.…”

“…[10][11][12] The wind driven ambient noise, manifest dominantly in the spectral band of 3-10 kHz, that has a direct impact on the mid-frequency sonar used for military and non-military applications like anti-submarine warfare (ASW) missions, fisheries, geological exploration, navigation, and surveillance. [3][4][5][6][7] The novelty of this work is an estimation of ambient noise statistical characteristics in the frequency band of 3-10 kHz based on the probability distribution function (pdf) of the SST. A detailed analysis of the relationship between sea surface parameters like SST and wind speed has also been carried out to support the conclusions.…”