An improved signal envelope estimation method for analysis of acoustic signals emitted by remotely piloted helicopters

This study presents a new signal envelope estimation method in order to improve the performance of the Empirical Mode Decomposition (EMD), especially in dealing with transient signals. An important application of this method is the analysis of signals containing spikes such as acoustic signals. For this purpose, both the spline interpolation and control point selection algorithm are adapted. To construct signal envelopes, the Catmull-Rom spline interpolation is employed due to its desired features. Also, a new algorithm is utilized in order to select control points prior to the iterative sifting process. Afterward, the proposed method is verified by some benchmark signals. Performance indices indicate that the proposed EMD outperforms the traditional one in handling transient signals. Finally, the proposed method is applied to acoustic signals gathered during some flight tests of a remotely piloted helicopter. The results demonstrate that the proposed method is able to isolate acoustic signals emitted by dissimilar sources.