This method, illustrated in Figure 5-74, is effective for laminate, doubler, and skin-to-closure-member bonds when
access to the backside is available. If the inspector can dampen the multiple echoes from the far side of the bonded
structure with a wet finger, then the bond is good. Otherwise the sound is being reflected by an unbond and is not
reaching the far surface, so it cannot be damped. Unbonds equal to or larger than the size of the search unit are easily
Figure 5-74. Damping Method.