According to McCann and McCann (1969), the attenuation for sediments 

 of mean diameter less than 0.0017 cm may be calculated from the equation 

 below assuming that the clay particles and water behave together as a 

 fluid of density 1.35 gm/cnw and viscosity of 0.015 poise. 



2a = cknCaj-l)^ —~z o"- 



n d { S 2 + (a d +T) 2 } 



where c = volume concentration of particles 



a = attenuation coefficient 



k n = (jj/c = wave number 



^d = Ps/Pf 



where p s = density of particles 



Pf = density of suspending fluid 



9 



(31) 





4r p /gj/2v * r„ /uj/2\ 



T = 0.5 + 9/(Ar p /oj/2v) 



rp = particle radius 



v = kinematic viscosity of the fluid 



co = angular frequency 



c c = velocity of compressional waves through the 

 suspension 



Therefore, viscous dissipation of the compressional waves occur. The 

 theory is valid from experimental evidence for the frequency range 

 30-370 kHz. 



For sediments of mean diameter greater than 0.0017 cm, the attenua- 

 tion coefficient is given by the sum of a viscous term plus a solid friction 

 term as 



2a = Kj_f + K 2 f 1/2 (32) 



where K^ , K 2 are constants and f is the frequency (kHz) 



21 



