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Ocean Ambient Noise Study in the Vicinities of Taiwan: Data Analysis and Numerical Modeling
Date Issued
2007
Date
2007
Author(s)
Chan, Hsiang-Chih
DOI
zh-TW
Abstract
This study is to survey the variant characteristics of ocean ambient noise in the vicinities of Taiwan and to understand their effects on detection ranges of active and passive sonar system. The data from the experiments of ASIAEX, VANS, and OAJEX are analyzed by statistical methods to obtain varying characteristics of noise levels. The first study is to analyze the ASIAEX data that were measured on the continental shelf, which indicates the minimum frequency-dependence of wind-wave noise is about 500 Hz. The noise level slopes in noise spectrum are changed with sea states. The standard deviations decrease significantly while wind speeds are over 5 m/s. The uncertainty from noise variance may increase due to the statistical duration. There are some distribution variations of ocean ambient noises in the vicinities of Taiwan. The second study is to develop a noise numerical modeling to simulate the sea surface noise fields. The results show the changes of noise source strength from sea surface are the main factor, and the changes of sound speeds due to nonlinear internal waves in ocean are the second factor. The comparisons of resultes on simulation and data have provided good confidence in this noise modeling, which can be applied to predict noise levels. Moreover, the ASORPS study cases explain the prediction errors and the uncertainty of noise levels on detection ranges of sonar. The results show the errors in the noise levels prediction in the vicinities of Taiwan by using the present empirical formula are a little high. So this study provides a development method that is to construct a database of ocean ambient noise, which integrates with statistical results of measurement data and simulations of numerical model. The mean and standard deviation of noise levels would be provided for ASORPS to improve the prediction performance of sonar.
Subjects
海洋環境噪音
聲納偵測距離
噪音數值模式
風浪
非線性內波
Ocean ambient noise
Sonar detection range
Noise numerical modeling
Wind-wave
Nonlinear internal waves
Type
thesis
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Name
ntu-96-D91525003-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):168b75319a9be3e47c048ef91690f209