The Measure And Identify On Engine Surface Radiate Noise

The first task for noise control purposes is to identify the part which radiate noise well and the major noise sources. In order to control the noise level, it is important to take the corresponding methods depending on the characteristics of major engine noise sources . The acoustic signals which obtained from a diesel engine contain many useful major noise sources information which often exists in the form of short duration transients to reflect the engine operating conditions. Because of the complex multi-excitations caused by engine structural and energy transform procedure, its non-steady working process and non-liner system behavior, the traditional analytic theory and methods in acoustic signals not suit to describe this complex situation.The major noise sources of engine and the bringing causation are analyzed in this paper. The theory and method of sound intensity are also introduced. In addition to, a measure project is set for one engine and sound intensity is measured.The acoustic signals obtained from engine are non-stationary transient. Compared with the FT, the wavelet transform has many distinct advantages for acoustic signal analysis. In this part, we make detailed discuss on the excellence of the wavelet analyze. A method to determine the maximal and the minimal scale parameters in the wavelet transform calculation is put forward. Based on the practical problems of engine acoustic source identification, describing method which apply to the actual application for wavelet analysis is put forward and the wavelet transform in engine acoustic source identification and acoustic field analysis for one engine is made. In addition to, some important acoustic sources are identified. Then it offers gist for controlling of engine noise.