1497 
Combining equations (25) and (26) we have: 
oy 2 par (27) 
on (28) 
4.2 Considering the situation in which Co > Ci there are 
three distinct cases for which the equations must be solved: 
Case (1) : / PQS HF 
Case (e)) ba te ee Se See 
Cases) > foS> | .= Cyes 
Comparison with the previous derivations shows 
that , corresponds to the sine of the angle of incidence, i.e. 
g = sin 8 - In case (1) both equations (27) and (28) are of 
the hyperbolic type; physically this corresponds to the situation 
in which 8 is less than the critical angle since i is less than 
C,/Cp- The solution for case (1) must therefore prove to be the 
usual undistorted acoustic reflection. 
In case (2) eauation (27) is hyperbolic while 
equation (28) is elliptic. This corresponds to the situation in 
which @, lies between the critical angle and 77/5, and the 
solution corresponds to that developed in Section 2 above. 
In case (3) both equations (27) and (28) are 
elliptic, and do not describe any real physical situation since 
sin 6, exceeds unity. (It can be shown also that the only 
