Data Collection. To evaluate the effectiveness of
the currently most popular coin-tap methods and to seek
possible improvements, we compare the test results on
patched versus normal airplane skin, with different underskin
structure conditions. We name two typical types of
under-skin structure conditions: condition A as those points
close to some supporting joists and condition B as those
points relatively far away from any supporting components.
Through the dual-channel audio input port of the SGI
Indy workstation, we recorded both the acceleration and
corresponding sound data simultaneously, of some chosen
typical normal airplane skin and typical patched skin, with
under-skin structure condition A and condition B respectively.
The sampling rate is 48 kHz