A Multipath Calculation of Surface-Generated Underwater Acoustic Ambient Vertical Directivity
Abstract
A general calculation of the spatial correlation function due to a distributed acoustic source near the water surface has been done previously using normal mode theory. In this paper a multiple ray path analysis is used to calculate the acoustic ambient vertical directivity function. Multipath propagation and ambient directional functions are physically intuitive concepts to underwater acoustic theory, and direct application of these notions has advantages in the interpretation of data. Existing procedures and computer code were used to expand the received pressure field, from a distributed source, into a sum of terms interpreted as multiple propagation paths. Standard forms for the source function and a geometric transformation were used to convert the pressure field to a solid-angle density function. Surface roughness, bottom geoacoustic parameters, and sound velocity/depth profiles measured in the Tongue of the Ocean in The Bahamas, were used in the calculations to predict hydrophone array performance in that area. Directivity function versus elevation angle and frequency are displayed for observers above and below a surface duct. A path-by- path contribution to the vertical distribution of energy is discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 18, 1988
- Accession Number
- ADA203770
Entities
People
- Robert M. Kennedy
- Thomas K. Szlyk
Organizations
- Naval Undersea Warfare Center