1447 
disturbance travelling with speed a of sound in the medium 
behind the shockfront which flows with flow velocity wu has 
propagated from P to P, and this distance ds can be de- 
de = Vdt « dt {x vw @D + fa*- uw Am’ O 5 
The angle @ between ds and dr just has to be the 
termined as 
critical angle, derived in Section IV: if a free surface would 
have been produced along ds, the attenuation by the reflected 
wave would just have the same speed of propagation in this direc- 
tion as the point of intersection between incident wave and the 
imagined surface. Therefore it is easy to derive the following 
equations: 
[ : 
a t- & aa - say (17) 
Wh 
a= 
r 
N) 
fron = @ D-uye 
ESA i o Sy i-(®) 
(17a) 
Since a, u, and D are known as functions of the pressure 
7 , equation (17) can be considered as differential equation for 
y = y(r), that is, for the boundary of the range of distortion; 
the charge depth d is acting as parameter. 
A general solution of (17) will be difficult. However, 
simpler solutions can be obtained for the case 7 < 500 at, because 
the approximations(2), (4), and (5) can be used. If (9) and (14) 
19 
