*4.3. Ensemble EMD*

EMD is often used as a signal disassembly method. EMD is used to decompose mixed signals of different scales into different IMF components. However, a limitation of this approach is the phenomenon called 'mode mixing'. Specifically, during the EMD process, a low-amplitude oscillation or an intermittent signal may exist in several IMF components; for example, a single modal component may be decomposed into different IMF components, or a single IMF component may contain two different modal signals, resulting in mode mixing within the IMF component. To solve this issue, Ensemble EMD (EEMD) is proposed [61]. When EEMD is performed, a white noise *wi*(*t*) signal with a limited amplitude is added to the original signal *X*(*t*); thus, the original signal is transformed as

$$X\_i(t) = X(t) + w\_i(t) \tag{16}$$
