Effects of Medium Fluctuations on Underwater Acoustic Transmissions in a Shallow Water Area

  • Erik Sevaldsen
Part of the NATO Conference Series book series (NATOCS, volume 5)


The paper describes a series of measurements in a shallow water area south of Elba, Italy, in 1977–78. The purpose of the experiment was to study the variability of one-way transmitted signals in shallow waters with
  • time (duration of individual experiments and season of the year)

  • space (source location, source and receiver depth)

  • center frequency of transmission (1 to 6 kHz)

Fluctuations are observed both in amplitude, frequency and phase (delay) of a signal. As a combined measure of fluctuations we used spreading functions and their widths in frequency and time. We also measured transmission loss and transmission loss time variations over the duration of individual experiments (30 minutes). The results showed small spreading in time. Three different classes of frequency spreading ranging from less than 50 mHz to more than 1 Hz were observed. Sea surface roughness has been identified as one source of fluctuations. Mean transmission loss is found to be rather high and seems to be more dependent on bottom properties than on range.


Internal Wave Transmission Loss Sound Field Small Spreading Shallow Water Area 


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Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • Erik Sevaldsen
    • 1
  1. 1.Norwegian Defence Research EstablishmentDiv. UHortenNorway

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