Figure 1
From: Seizure classification in EEG signals utilizing Hilbert-Huang transform

Comparison between Hilbert-Huang Transform (left) and wavelet Transform (right). Comparison between Hilbert-Huang Transform (left) and wavelet Transform (right) when applied to the same signal (black). Frequency modulation is tracked precisely by Hilbert-Huang (yellow curve) while the resolution constraints and resultant harmonics prevent accurate tracking of frequency modulation by wavelet transform.