Variability of Acoustic Transmissions in a Shallow Water Area,
Abstract
A series of experiments on the variability of acoustic transmissions in a shallow-water area is described. The variables considered have been time (short period and seasons), frequency of transmission (1 to 6 kHz), and space (location and depth of source, depth of receiver). The variability has been studied mainly in terms of transmission-loss fluctuations and spreading in frequency and delay of phase-coherent pulse signals. Short-period transmission-loss fluctuations have generally been found to be within + or 3 dB of the mean, with some few significant exceptions in summer. Delay spreading (3 dB) was found to be rather small, mostly near 5 ms, because there was usually only one strong arrival/arrival cluster. The measured frequency spreading can be classified in two groups, one showing very little spreading, Delta f sub epsilon (0.05 to 0.1) Hz, the other being much more spread, Delta f > 1 Hz. This is interpreted as the result of internal-wave action under the existing sound-propagation conditions, however, lack of environmental data prevents the provision of conclusive evidence for this explanation. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1981
- Accession Number
- ADA103278
Entities
People
- Erik Sevaldsen
Organizations
- SACLANT ASW Research Centre