SPINDEL: PHASE FLUCTUATIONS, COHERENCE AND INTERNAL WAVES 



frequency cut-off is quite clear and dramatic. This is only one illus- 

 tration of our present lack of understanding and consequent inability 

 to predict and forecast. 



A firm connection between oceanographic effects and acoustic 

 effects must be established to allow the most effective exploitation 

 of ocean transmission paths. Well controlled experiments are necessary 

 to sort out the host of contributing factors such as microstructure, 

 internal waves, cyclonic and anti-cyclonic eddies. Experiments must 

 be conducted in a variety of locations to learn whether results at 

 one point can be extrapolated to another. Similarly, experiments 

 must be conducted at a variety of frequencies and ranges to establish 

 the scaling laws so necessary for accurate prediction. Perhaps most 

 important of all, however, is the need to coordinate acoustic experi- 

 ments with strong physical oceanographic programs, so we can signifi- 

 cantly increase our understanding of acoustic variability. 



REFERENCES 



Baer, R. N., and M. J. Jacobson, "Analysis of the Effect of a Rossby 

 Wave on Sound Velocity in the Ocean," J. Acoust. Soc . Am. 55, 

 1178-1189, 1974. 



DeFerrari, H. A., "Effects of Horizontally Varying Internal Wave 

 Fields on Multipath Interference for Propagation Through the 

 Deep Sound Channel," J. Acoust. Soc. Am. 56, 40-46, 1974. 



Franchi, E. R. , and M. J. Jacobson, "An Environmental-Acoustics Model 

 for Sound Propagation in a Geostrophic Flow," J. Acoust. Soc. Am. 

 53, 835-847, 1973. 



Garrett, C, and W. Munk, "Space Time Scales of Internal Waves," 

 Geophys. Fluid Dynam. 2, 225-264, 1972. 



Porter, R. P., R. C. Spindel, and R. J. Jaffee, "CW Beacon System 

 for Hydrophone Motion Determination," J. Acoust. Soc. Am. 53 

 1691-1699, 1973. 



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