- 1^2 - 



aligned with arm 2 whereas there are relatively large slope (and 

 pressure) differences along the wave ray — aligned with arm 3. (See 

 Figure VI-15.) 



As is illustrated in Figure 



VI-14, one expects that the wave 



frequencies of greatest energy should 



be the same for both the water 



surface displacement and slope terms. 



It is instructive to note, however, 



that greater energy appears in the 



higher frequency bands of the slope 



spectra than in those of the wave piGURE VI-15: Wave crest ap- 

 proximately aligned with 

 spectrum. This too is an expected .p2 arm 



result since the energy spectrum of 



of slope (developed from a differential pressure signal) differs from 



that of water surface displacement (generated from the absolute 



pressure signal) by a factor of wavenumber-squared. The energy 



spectrum of the water surface displacement is developed through the 



frequency-by-frequency division of the dynamic pressure energy 



spectrum by the specific gravity of seawater (squared) and the square 



of the pressure response function, Kp. The water surface slope 



energy spectrum is similarly developed through the division of the 



differential pressure energy spectrum by the squares of the specific 



gravity of seawater and the pressure response function. The energy 



