海床地音參數之反算與資料庫建立

Abstract

台灣周邊海域由於水面聲速高，聲波折射強，水深淺於5000公尺以下的深度聲波都會在海底反射，因此在台灣周邊海域做聲學研究時，地音參數就變的格外重要。 過去之研究主要使用3.5kHz之窄頻脈波訊號以頻譜比對法反算底質參數(壓縮波之衰減係數)，目前底質探測方面，海研一號及達觀艦都已進步到使用連續變頻聲納(Chirp Sonar)系統。惟國內尚未使用以上兩種系統資料使用頻譜比對法作反算，因此本文第一部份為建立一快速反算聲波衰減程式，應用於海研一號Chirp Sonar之資料分析。資料分析所取點位均為不同之底質類型，其結果分析與實測資料比對，誤差範圍均在15%以內。 另外，本文亦提供台灣周遭海洋環境之地音模型建立的方式，再導入聲波衰減係數以建立聲學地音參數之能量。最後一部分為提出地音參數資料庫之架構，利用第一部份頻譜比對法的方式將衰減係數K值求出，進而將其值導入地音模型之中，以獲得聲學所需之地音參數，支持地音參數資料庫的建立。

The fast sound speed at sea surface in the waters surrounding Taiwan causes strong refraction of sound waves. If water depth is less than five thousand meters, the sound waves will be reflected at the seafloor. Therefore, geo-acoustic properties are important to the acoustic study in the water surrounding Taiwan. This thesis composes of two major works. Part I is the inversion of pressure wave attenuation coefficient from chirp sonar data. Part II is to establish the geo-acoustic model for different sediment types, thus to provide for the Advanced Sonar Range Prediction System (ASORPS). In the past, has been used spectral ratio technique obtain geo-acoustic parameters from 3.5 kHz sonar data. Now the sediment exploring technique has already advanced using chirp sonar system on Ocean Researcher I and Ta Kuan’s TOPAS system. The data of chirp sonar collected in Ocean Researcher I has not been analyzed to retrieve the geo-acoustic parameters yet. Therefore, one part of this study presents the estimation of attenuation coefficient of the seafloor sediment obtained by analyzing the Ocean Researcher I chirp sonar data. The results are compared with the core data, and the error is within 15%. Another purpose of this research for the geo-acoustic model of Taiwan's surrounding sea was to establish information needed. Also, the concept and framework of a geo-acoustic database is proposed.