1399 
Poi 
cing, of agneeees 
Angle o 
incidence 
Tension 
front 
Fig. 3. Schematic Diagram of S -R os 
Wave Paths. g urface-Reflection Shock 
This measurement was chosen in preference to the time 
between the arrival of the wave fronts at the front edge of 
the gauge because the dropeoff due to the tension wave becomes 
gradual for increasingly oblique incidence and the choice of 
the point at which the normal free~water decay ceases becomes 
correspondingly unreliable, 
Even in the acoustic region, the time, Tp, of the tension 
cut-off is longer than the crossing time, Tg, of the initial 
pressure wave. 
(A) (B) 
Fig. 4+. Typical Pressure-Time Curves 
yn 
