Study on the marginal spectrum in Hilbert-Huang transform

To further understand and correctly master the notion of marginal spectrum in Hibert-huang Transform (HHT), the linear property of marginal spectrum is demonstrated, an mistake to the notion of marginal spectrum in some documents is pointed out, and a new viewpoint about the essential difference between marginal spectrum and Fourier frequency spectrum is put forward by which the amplitude of Fourier frequency spectrum only represents the probability that a frequency objectively exists in a signal while the amplitude of marginal spectrum decides whether a frequency objectively exists in a signal. According to the linear property of marginal spectrum, the physical meaning of marginal spectrum is further given by which a amplitude of marginal spectrum is the sum of amplitudes of the corresponding frequency at all time. The advantage of marginal spectrum in application is validated by an actual vibration signal.