An analysis of the effects of energy spreading loss and transmission loss on low frequency active sonar operations in shallow water
By: Brian S. Adams
Contributors: Naval Postgraduate School (U.S.) ; Naval Postgraduate School (U.S.) 
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1997
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 65
Description: Energy Spreading Loss (ESL) is qualitatively defined as the reduction in peak power level due to energy      spreading of a transmitted acoustic pulse in tune. An analysis of the impact of bathymetric geometry and      sediment type on ESL and TL associated with the Low Frequency Active/Compact Low Frequency Active      (LFA/CLFA) sonar operations was conducted utilizing the FEPE, FEPE_SYN and EXT_TD programs to      model the time spreading of the acoustic pulse due to multipath propagation in shallow water. Both a      Blackman windowed pulse and a Continuous Wave (CW) pulse were used in this analysis. The Blackman      pulse had a center frequency of 244 Hz with a bandwidth of 24 Hz. The CW pulse had a center frequency      of 244 Hz with a bandwidth of 0.0625 Hz. Model inputs were a geoacoustic description of the Tanner Bank      region off the coast of San Diego and a typical late summer sound speed profile taken from the MOODS      database. ESL and TL's impact on low frequency active sonar operations was determined as a function of      bathymetry, sediment type, sound speed profile, and pulse length. The results showed that ESL is inversely      related to pulse duration and at low frequencies is relatively uninfluenced by sediment type. When pulse      lengths were reduced to less than 1 second, ESL became appreciable ( > 6 dB one way) and was an      important segment of the active sonar equation. TL was found to be the dominating factor in LFA/CLFA      operations for pulse lengths greater than 1 second and was greatly influenced by sediment type and sound      speed profile.
Notes: "September 1997."

Thesis advisor(s): Robert H. Bourke, James H. Wilson.

Thesis (M.S. in Physical Oceanography) Naval Postgraduate School, September 1997.

Includes bibliographical references (p. 63-64)

Approved for public release; distribution unlimited.

Also available online.

Mode of access: World Wide Web.

System requirements: Adobe Acrobat reader.

US Navy (USN) author.

dk/dk cc:9116 04/17/98.