Improved analysis of noise emitted by reciprocating machinery

摘要

Reciprocating machinery as, e.g., engines, gearboxes, and compressors represent an important class of noise sources. A traditional approach to the analysis of these sources is to assume that the noise they emit is stationary. However, in this waya certain amount of information on noise sources, regarding, e.g., events timing, is lost. Due to cyclic working process of the reciprocating machinery the noise they emit is nonstationary with periodic structure. This nonstationary periodic structure, which is partially suppressed in the traditional approach, can be exploited for obtaining amore detailed description of the noise source. Noises with periodic structure can be considered to be a special subclass of cyclostationary signals. Cyclostationary signals have been studied in communications [1-4] and in geophysics [5] extensively for years. Unfortunately, not too much attention has been paid to them by noise engineering community, though they can be exploited conveniently even here, as shows an example of diagnosis of car engines [6]. In the paper a suitable statistical characteristics of cyclostationary signals are reviewed and methods for their computation are mentioned. As a concrete example, passenger car gearbox vibration is analysed and the results of both stationary andnonstationary approach are compared.