Accession Number:

ADA230010

Title:

Source Imaging and Sidelobe Suppression Using Time-Domain Techniques in a Shallow-Water Waveguide

Descriptive Note:

Abstract

Corporate Author:

NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS

Personal Author(s):

• Feuillade, C.
• Clay, C. S.

Report Date:

1990-01-01

Pagination or Media Count:

1.0

Abstract:

Source localization in a shallow-water waveguide, using harmonic cw techniques, is typically complicated by the repetitive sidelobe structure of the acoustic field. For this reason, much interest has been shown recently in the development and implementation of time-domain methods, which should achieve better performance because of their additional frequency-averaging capability. In a previous publication C. S. Clay, J. Acoust. Soc. Am. 81, 660-664 1987, the basis for optimum signal transmission and source localization in a waveguide using time-domain techniques was described. In the work reported here, using a simple two-layer model with shallow water depth 20 m and short range 1500 m, the variation in time-domain source image resolution and sidelobe suppression as a function of frequency bandwidth, mode selection, and hydrophone receiver emplacement has been investigated. the results indicate that source localization performance is most strongly dependent upon the bandwidth and number of modes available to carry the signal transmission. The physical mechanism for narrowing the source image and suppressing sidelobes is spatial averaging of the acoustic field due to variation of the horizontal wave numbers for the modes as a function of frequency. Improvements in mode sampling, by increasing the number of receivers, also served to reduce the level of sidelobes, but did not improve the resolution of the image. jhd

Descriptors:

• *FREQUENCY
• SPATIAL DISTRIBUTION
• OPTIMIZATION
• PHYSICAL PROPERTIES
• RESOLUTION
• WAVEGUIDES
• SHALLOW WATER
• WAVE PROPAGATION
• IMAGES
• SAMPLING
• CLAY
• SHORT RANGE(DISTANCE)
• HORIZONTAL ORIENTATION
• MEAN
• HYDROPHONES
• BANDWIDTH
• NUMBERS
• TIME DOMAIN
• SELECTION
• WAVES
• SUPPRESSION
• SIDELOBES
• ACOUSTIC FIELDS
• SHALLOW DEPTH
• SOURCES

Subject Categories:

• Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE