Accession Number:

AD0753200

Title:

Some Measurements of Acoustic Normal Mode Propagation in Shallow Water

Descriptive Note:

Interim rept.

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

• Schuetz, A. E.

Report Date:

1972-11-16

Pagination or Media Count:

24.0

Abstract:

Experiments were conducted in the northern Gulf of Mexico during July 1969 and March 1970 to study propagation characteristics of acoustic normal modes. This shallow-water area had a constant depth 31 plus or minus 2.5 m over a propagation path of at least 20 km along a bearing line of 285 degrees T. Short-pulse, 3 cycle signals were emitted from 400- or 750-Hz center frequency sources. The vertical distributions of pressure amplitude of each of the two lowest order normal modes of these signals, measured by a vertical line of hydrophones, agreed well with distributions calculated by computer using a two- layer fluid model. Temporal variations of modal intensity averaged over depth for both the first and the second modes were observed for 7-min runs.

Descriptors:

• *UNDERWATER SOUND
• *MEXICO GULF
• MATHEMATICAL MODELS
• SHALLOW WATER
• UNDERWATER SOUND SIGNALS
• EXTREMELY LOW FREQUENCY
• ATTENUATION
• HYDROPHONES

Subject Categories:

• Physical and Dynamic Oceanography
• Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE