Enclosing damage diagnosis, this pape studies modal experiment in ambient excitation, optimal placement of sensors and structural damage alarming using wavelet packet energy spectrum.

At last, the experiment to testing is finished. The test indicates that the packet filter based on NDIS intermediate driver have the advantages of high efficiency and practicality.

Dynamic signals measured from experiment beams are first decomposed into wavelet packet components, then the wavelet energy rate index is computed and used to detect location of damage.