THE INTERPRETATION OF THE BISPECTRA OF VIBRATIONAL SIGNALS .1. THEORY

Bispectral analysis is emerging as a new powerful technique in signal processing, offering insight into non-linear coupling between frequenc ies and having potential applications in many areas where traditional linear (i.e. power spectral) analysis provides insufficient informatio n. However, it is more difficult to interpret bispectral features than power spectral features, and this has hindered the applications of th e theory. In this paper a normalised bispectral measure is used in the analysis of vibration signals containing periodic components and nois e. In Part I the bispectral features associated with various signal ty pes are derived, and practical considerations regarding the choice of sampling rate are considered. Part II describes the application of thi s theory to experimental data from a variety of vibration sources, and discusses the possible applications of bispectral analysis in machine condition monitoring.