*2.3. Impact Localiaztion Process*

The implementing process of the impact location method based on the proposed method is shown in Figure 2. The fast HHT with an optimized EEMD algorithm is introduced to extract IMFs from impact signals. The spatial spectrum **P**MUSIC of each IMF is evaluated versus all (*r*, *θ*) in the *r* − *θ* plane to find the steering vector **A**(*r*, *θ*) which matches the actual impact signal vectors. When the right steering vector is found, the denominator of Equation (2) approaches zero due to the orthogonal properties, resulting in a peak in the spatial spectrum which corresponds to the estimated impact position.

**Figure 2.** The impact localization process.
