Relationship between surface dynamics
and emitted sound
Comparing the results in the two tables, we notice that
while the distributions of normal skin and patched
skin have a large overlap for supported areas (underskin
condition A) in Table 1, a very similar situation exists
for the unsupported areas in Table 2. This means that the
coin-tap test method, either with force measurement only
or with sound measurement only, cannot always distinguish
different airplane skin conditions for some underskin
supporting structure conditions, and the discrimination capabilities of the force-only method and sound-only
method are very similar.