Methods For Pass-by Noise Measurement And Contribution Analysis Of Sound Sources Of Vehicles

The measurement standard of pass-by noise emitted by accelerating road vehicles requires that the vehicles must meet the requirements on the pass-by noise limits before being approved for the market.The Chinese national standard(GB 1495-2020)for the measurement of pass-by noise has been officially promulgated and implemented on 1 July,2020.The new standard puts forward more stringent requirements on the pass-by noise measurement of vehicles.It increases the difficulty of the outdoor pass-by noise measurement and reduces the qualification rate of measurement data,which results in more labor and time.And the outdoor pass-by noise measurement is easily influenced by the climatic conditions,which leads to a poor repeatability of the measurement results.Moreover,in order to strengthen the management and control of traffic noise,the new standard has further reduced the pass-by noise limit,which undoubtedly brings a big challenge to the homologation of new vehicle for automotive manufacturers.Therefore,the research on the measurement methods and the contribution analysis of sound sources of pass-by noise of vehicles can provide technical guidance to the outdoor pass-by noise measurement and has important theoretical value to quickly evaluate the pass-by noise in the early stages of design and formulate corrective measures to reduce the pass-by noise.In recent years,although the domestic and foreign scholars have proposed a variety of methods for the measurement of pass-by noise and contribution decomposition of sound sources,these methods still have some inadequacies in the evaluation accuracy or efficiency.Therefore,in this dissertation,problems existing in the measurement methods of pass-by noise and the sound source contribution analysis based on the Operational path analysis with exogenous inputs(OPAX)method are deeply investigated and discussed.The specific requirements and difficulties in the outdoor measurement of pass-by noise based on the new standards(GB 1495-2020)are analyzed.A series of indoor measurement methods of pass-by noise of vehicles are proposed.And the contribution decomposition model of sound sources of pass-by noise is established.The main contributions and achievements of this dissertation are summarized as follows:(1)The differences in the measurement requirements,measurement aspects and calculation methods of pass-by noise between GB 1495-2020 and GB 1495-2002 are compared and investigated.And the problems and challenges of pass-by noise measurement under the new standard are analyzed.Subsequently,the outdoor pass-by noise measurement experiment according to GB 1495-2020 is carried out,and the differences on the pass-by noise measurement results between the new and old standards are compared,which provide standard reference results for the following research on the indoor pass-by noise measurement methods and have important guiding significance to the outdoor pass-by noise measurement.(2)An indoor measurement technique based on the drum coast-by experiment approach is proposed,which solve the problem of the influence on the measurement accuracy of pass-by noise.The effectiveness of the proposed method is verified by the indoor pass-by noise measurement.And the superiority of the proposed method is demonstrated by comparing with the experimental results of the shielding method and slick-tyre experiment method advised in the ISO 362-3 standard.(3)An approach for the indoor measurement of pass-by noise based on interpolated time-domain equivalent source method(TESM)is proposed,which avoids the problem that the indoor pass-by noise measurement method based on the microphone array technique depends upon the dedicated large-scale semi-anechoic chamber.The influence of equivalent source arrangement scheme on the calculation results of pass-by noise is investigated through the numerical simulation,and the feasibility of the proposed approach is demonstrated by numerical simulations and experiments.Considering that the vehicle is moving in the measurement process of pass-by noise,the sound emission calculation of moving sources is introduced into the TESM,and an approach for the indoor measurement of pass-by noise based on TESM is proposed in which the influence of vehicle movement is considered.It can directly obtain the pass-by noise which eliminate the truncation and recombination error of the array signals,and also can naturally incorporate the Doppler effect caused by the vehicle motion.This can help to improve the measurement accuracy of the pass-by noise.And its validity and advantages are demonstrated respectively by numerical simulations and the real vehicle experiment.(4)An OPAX method based on the moving multi-band model is developed to analyze the source contribution of pass-by noise.In this method,a statistical metric is introduced to quantitatively evaluate the estimation uncertainty,which realizes the stable iterative solution of the load parameters and further improves the contribution decomposition accuracy of sound sources of pass-by noise.The validity of the proposed method is confirmed by the numerical simulation and experiment carried out with the real vehicle experiment.