Test Analysis And Loudness Identification Of Bus Interior Speed-changing Noise

Automobile noise increasingly become the main factor of city environmentpollution, human physical and mental health damage and the reduction of workefficiency. Now the noise reduction is taken by enterprises to improve their productcompetitiveness, and is the government’s main strategy of solving the pollution of noise.It is well known that the primary condition of noise control is effectively implement ofnoise source identification. Thus the reasonable noise reduction measures can be givenand then should evaluate the effect of the measures. The traditional signal analysis tonoise identification can now not effective reflection the subjective feeling of noise, alsocannot obtain straightforward results of noise evaluation. But the identification methodwhich based on the ear hearing mechanisms can get a real and quantitative reaction ofnoise’s energy which likes in the human ear.To solve the problem of abnormal noise which obvious appeared in some drivingconditions of a domestic hybrid electrical bus, we used two methods to analyze thenoise mechanism: first is the traditional signal analysis method based on the physicalcharacteristics of noise; second is specific loudness method which accord with thehuman hearing mechanisms. The results found that those two methods can successfulprove that the transmission vice box’s bevel gear is source of abnormal noise, buttraditional identification method can only achieve the equal effort of loudness’ bycombining with interactive filtering technology. Based on the result of identification,measures such as improving gear processing technology and so on were proposed. Atlast the A-weighting level and total loudness were used to evaluate the effort of noisecontrol. The evaluation result shows that the noise control measures get a good noisereduction effect, and the loudness’ identification results is more straightforward. Themain contents includes：1) In order to acquire the abnormal noise signal of HEB, the noise testing plan forroad test and transmission bench test, and the software and hardware for noise testsystem were established. Thus the noise tests for particular condition were completed.2) A preliminary analysis which aimed to the noise frequency characteristic ofdifferent condition to noise signal were proceed, including short-time Fourier transformmethod and interactive filtering method. The results found that the reason fortime-varying noise is primary related to the bevel gear in the transmission vice box. 3) Consider to the issue that only rely on physical property of signal to noiseidentification can’t fully reflect the human subjective feeling to noise, the steady andinstantaneous Moore’ loudness model for noise analysis were established based on theAmerican national standards ANSI_S3.4₂005. And those model were used to analysisand verify the result of noise identification. Then the subjective and quantitativeevaluation for noise control were proceed by means of A-weighting level and Mooreloudness, the feature of those two method was also analyzed.4) A rapid and effective noise signal analysis system which integrated the signalanalysis method as above-mentioned was built on FAMOS software platform. Thismodularization software can be easily used to process mass noise signal, which cangreatly improve the efficiency of data processing.