本研究之目的乃在於探討各種隨機聲源對海表面所產生環境噪音的影響。環境噪音的來源包含天然與人為因素，天然的噪音來源包括地震活動、風浪對海面的擾動等；人為噪音來源主要乃由船隻的活動所引起。以上所提及之噪聲源各有其特殊的頻率與強度，依聲源的結構大致可分成兩大類，一為離散式聲源，一為連續式聲源。離散式聲源乃如船隻及生物噪音，其所發出之聲源可視為單點聲源；而風浪於海面所造成的噪音則屬連續隨機聲源，此種聲源即為本研究主要探討之環境噪音來源。本研究引用 Kuperman 和 Ingenito 於 1980 年提出一海洋環境噪音模擬簡化模式，作為環境噪音模擬的基礎。該模式將海面所產生的噪音用一接近海面的連續單點聲源（continuous monopoles）來表示，並使用白噪音（white noise）譜來做模擬，經由理論的推導，建構一環境噪音強度與空間分佈特性之運算公式。
本研究乃基於白噪音譜並不符合真實海洋環境，故引進較廣為使用之頻譜－高辛（Gaussian）頻譜與符合真實環境之頻譜－皮爾生-莫斯考維茲（Pierson-Moskowiz）頻譜。本研究與過去研究不同之處，乃在於本研究建立了更符合實際海洋環境的模式，來探討海表面不同噪聲源分佈對於海洋環境噪音的影響。為簡化環境，本研究將水層與底床中聲速與密度皆假設為常數分佈，沉積層中聲速則為符合真實環境之反平方(inverse-square)分佈，密度為廣義指數(generailzed exponential)分佈。本研究中我們分別探討了白噪音譜、高辛頻譜以及皮爾生-莫斯考維茲頻譜三種模式，利用不同頻率、不同風速、不同相關長度等相關參數，來模擬及分析海洋環境噪音場，探討不同噪聲源對於環境噪音強度及空間關聯函數的影響，並將計算結果與現有文獻及研究結果做比較。

Ambient noise generated by surface random processes is the primary contribution to the noise-field energy in the intermediate frequency band, and thus is important in many applications of underwater sound. In this study, the noise field is analyzed with respect to the effects of random source spectrum, waveguide structure of the water column, and seabed stratification upon the noise-field intensity as well as spatial correlation. Based upon a noise-generation model due to continuous random sources, incorporating several analytical models for seabed stratification, a formulation may then be derived to facilitate the numerical implementation. Many results shall be generated and analyzed.
In this study considers the noise field generated by surface random processes in an oceanic environment with a sediment layer possessing a continuously varying density and sound-speed profile. This model closely resembles the oceanic waveguide environment and therefore enables the simulation of surface noise generation. Many results of the noise field were generated, including the noise intensity distribution, vertical and horizontal correlations. It is demonstrated that the noise intensity may be affected by the stratification mainly through the continuous spectrum, in that the continuous spectrum is equally important as the normal modes in the present analysis. Moreover, the results for the correlations show that the noise field in the horizontal direction becomes more coherent when the noise sources are more correlated, while in the vertical direction, the results tend to reverse. The horizontal correlations of the noise field due to surface random sources with non-isotropic power spectrum, such as nonisotropic Gaussian and Pierson-Moskowitz, were generated and analyzed.

第一章 緒論 1
1.1 研究主題與研究動機.................................1
1.2 文獻回顧...........................................4
1.3 研究方法...........................................5
1.4 論文範疇...........................................6

第二章 理論模式 7
2.1 簡介...............................................7
2.2 聲波方程式.........................................8
2.2.1 均勻介質....................................8
2.2.2 非均勻介質.................................10
2.2.3 整理.......................................11
2.3 聲波方程式之通解..................................12
2.4 海洋隨機聲源所產生之噪音場........................13
2.4.1 噪聲強度...................................16
2.5 結語..............................................17

第三章 海表面之隨機聲源 18
3.1 隨機過程與隨機場..................................18
3.1.1 高度概率密度函數與分佈.....................20
3.1.2 波譜.......................................21
3.2 波數譜與隨機場....................................24
3.3 高辛波譜模式......................................32
3.4 皮爾生-莫斯考維茲波數譜模式.......................36

第四章 噪聲場數值模式 43
4.1 各層聲波方程式的解................................43
4.1.1 均勻介質...................................44
4.1.2 非均勻介質.................................45
4.1.3 整理.......................................49
4.2 邊界條件..........................................49
4.3 基準驗證..........................................51

第五章 結果與討論 55
5.1 噪聲強度..........................................55
5.2 空間相關性........................................61
5.2.1 水平相關...................................61
5.2.2 垂直相關...................................66

第六章 結論與建議 68
6.1 結論..............................................68
6.2 建議..............................................69

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