Hilbert-Huang transf..

40 H. Ding et al. / Flow Measurement and Instrumentation 18 (2007) 37–46
Fig. 2. Comparison between the IMF components and wavelet components of the differential pressure fluctuation signals from the 25 mm-diameter pipeline: (a)–(d)
the IMF components; (e)–(h) the wavelet components.
a series of scales that cannot reveal precisely the relationship
between time and instantaneous frequency [4]. The smaller
scales represent the high-frequency information in the signal
and the larger scales represent the low-frequency information
in the signal.
In this study, the energy distribution H j of different
frequency bands is defined as
H j = E j
E
( j = 1, 2, 3) (15)