In this paper some techniques are presented which have not been 

 considered before for use in the theoretical and experimental investiga- 

 tions of fluctuations in pressiire at the bottom of the ocean. Ihe limita- 

 tions of such procedures are discussed and some sample results are shown* 



B. PRESSUR3 POWER SPECTEUM 



It is assumed that the pressure variations at a given depth are essen- 

 tially reflections of the features existing at the surface of the ocean« 

 Consider then, the energy spectrumj namely the pressure power spectrum, 

 formed as a result of the wave action on the surface. If the formation is 

 governed purely by attenuation of the surface profiles, the pressure varia- 

 tions will be given by 



where A (A) is the power spectrum of the sea surface, K is the attenua- 

 tion factor, and Ap(jU,) is the residual energy at depth d. Theoretically, 

 a family of curves can be derived from equation (l) by var;ving the depth. 

 i/iThen the depth considered is equivalent to the depth from the still-water 

 level to tlie bottom, the attenuating factor is 



K^ . [ _ a) 



where L. is the wave length associated with the spectral period, \ ^ and 

 a is the depth of water. 



In practice, i^TTu / L is obtained from a knowledge of d / Lo j, 

 where L = 5.V5lT^s ^^'^ deepwater vrave length. These quantities and other 

 related factors have been tabulated by Wiegel (1948). 



The functional relationship between Ap( Lt) and A ijU-) defines the 



2 



