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NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS ACOUSTIC PROPAGATION LOSS MODELING FOR DABOB BAY, WA by John R. Mitchell September, 1991 Thesis Advisor: 0. B. Wilson, Jr. Approved for public release; distribution is unlimited. Unclassified SECURITYCLASSIFICATIONOFTHIS PAGE REPORT DOCUMENTATION PAGE UNCLASSIFIED a Report Security Classification 1b Restrictive Markings 2a Security Classification Authority 3 Distribution Availability of Report 2b Declassification/Downgrading Schedule Approved for public release; distribution is unlimited 4 Performing Organization Report Number(s) 5 Monitoring Organization Report Number(s) 6a Name of Performing Organization 6b Office Symbol 7a Name of Monitoring Organization Naval Postgraduate School (IfApplicable) 3A Naval Postgraduate School 6c Address (city, state, and ZIP code) 7b Address (city, state, and ZIP code) Monterey, CA 93943-5000 Monterey, CA 93943-5000 8a Name of Funding/Sponsoring Organization 8b Office Symbol 9 Procurement Instrument Identification Number (7/ Applicable) 8c Address (city, state, and ZIP code) 10 Source of Funding Numbers V ProgramElementNumber | ProWjecAtNo TaskNo WorkUnitAccession 1 1 Title (Include Security Classification) Acoustic Propagation Loss Modeling For Dabob Bay. 12 Personal Author(s) Mitchell, John R 13a Type of Report 13b Time Covered 14 Date of Report (year, month, day) 15 Page Count Master's Thesis From To September 1991 16 SupplementaryNotation The views expressed in this thesis are those ofthe author and do not reflect the official policy or position ofthe Department ofDefense or the U.S. Government. 17 Cosati Codes 18 Subject Terms (continue on reverse ifnecessary and identiWfyAby block number) Field Group Subgroup Acoustic Propagation Loss Modeling, Dabob Bay, I 19 Abstract (continue on reverse ifnecessary and identify by block number) An analysis ofthe acoustic sound propagation in a multipath environment in an ocean at short ranges has been conducted using a Modified Time Delay Spectrometry (TDS) and an experimental continuous-wave technique. WA Data from the acoustic range at Dabob Bay, were analyzed to determine the relative amplitudes ofthe direct- and surface-reflected signals. The results show that, at moderate ranges and typical source and receiver depths, the surface-reflected sound is a significant contributor to the received sound level. The theory supporting both techniques is presented. Discussions and conclusions are drawn. Recommendations for future investigation are made. 20 Distribution/Availability of Abstract 21 Abstract Security Classification X| unclassified/unlimited same as report DTTCusers Unclassified | J 22a Name of Responsible Individual 22b Telephone (IncludeArea code) 22c Office Symbol Prof. O. B. Wilson , Jr. (408) 646-2894 PH/W1 DD FORM 1473, JUN 86 Previous editions are obsolete. SFCURrTYCLASSIFICATIONOFTHIS PAGE S/N 0102-LF-014-6603 Unclassified Approved for public release; distribution is unlimited. Acoustic Propagation Loss Modeling For Dabob Bay, Wa. by John R. Mitchell Lieutenant, United States Navy B.S., Clemson University Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN APPLIED SCIENCE from the NAVAL POSTGRADUATE SCHOOL September 1991 ABSTRACT An analysis of the acoustic sound propagation in a multipath environment in an ocean at short ranges has been conducted using a Modified Time Delay Spectrometry (TDS) and an experimental continuous-wave technique. Data from the acoustic test range WA at Dabob Bay, were analyzed to determine the relative amplitudes of the direct- and surface-reflected signals. The results show that, at moderate ranges and typical source and receiver depths, the surface-reflected sound is a significant contributor to the received sound level. The theory supporting both techniques is presented. Discussions and conclusions are drawn. Recommendations for future investigation are made. ... 111 . n TABLE OF CONTENTS INTRODUCTION I. 1 A. Background 1 B. Objective 2 MULTIPATH PROBLEM DESCRIPTION II. 4 A. The Multipath Problem 4 B. Assumptions 4 C. Multipath Geometry 5 MEASUREMENT TECHNIQUES III. 8 A. TDS Technique 8 1 The Excitation Signal 8 2. Dynamic Signal Analyzer Operation 10 B. Continuous-Wave Method 12 MULTIPATH MEASUREMENT SYSTEM IV. 14 A. Test Configuration 14 B. Data Processing System 17 IV