h x (0) 

 (a) a = t 



r 



i p uu(0)-t i 



(b) Aft 



-fr, (0) 



K o 1 



Relation (69a) shows that the spatial attenuation factor 

 a is directly proportional to the resistive factor r , the 

 proportionality factor being dependent upon the resonant 

 mode and cavity dimensions. Using k (0) = n x n/^ yields 



P„«>(0) I 



(69) 



(70) 



where n is the integer characterizing the cavity mode in 

 the x direction. 



Relation (69b) expresses the change in k (0) due to the 

 fact that the wall takes part in the vibration. The equation 

 can be expressed in the form 



Afc x = -—. M 1 (71. 



where A I = m^ /p which represents the thickness of a 

 layer of the contained fluid, which has the equivalent mass 

 per unit area as the stainless steel sheet. Using the pre- 

 vious expression for k (0), the corrected k x is then given 

 by 



71, TT 



* = -7 7- (72) 



i I + A-t, 



in which the conventional relation for k is employed with 

 the actual t augmented by the correction A l ± . 



52 



