Study On The Formation Mechanism And Noise Reduction Function Evaluation Of Vibration/Pumping Noise Of Porous Elastic Road Surface

With the continuous improvement of urban road network and the sharp increase of car ownership,the problem of traffic noise pollution is becoming more and more serious.Its impact has gradually expanded from the single field of environmental noise pollution to the health of the whole society.Porous elastic road surface(PERS)is one of the most effective low-noise pavements to reduce traffic noise.However,the research on porous elastic road surface mostly stays in material gradation design and indoor mixture performance evaluation,and lacks in-depth research on the noise generation mechanism of the pavement.In addition,there are few application examples of porous elastic road surface engineering in China,so there are great limitations in the evaluation of its noise reduction function.Therefore,based on a series of indoor and outdoor acoustic tests and finite element numerical simulation methods,this thesis studies the noise reduction mechanism of porous sound absorption and damping vibration reduction of PERS pavement materials,analyzes the noise generation process of ’vibration/pumping’ noise of PERS pavement,and relies on physical engineering to conduct on-site noise test to evaluate the noise reduction performance of PERS pavement.The specific research contents are as follows :Firstly,the generation and enhancement process of tire road noise are analyzed theoretically,and the acoustic related tests of PERS pavement materials are carried out.The sound absorption coefficient,dynamic elastic modulus and phase angle of the specimens are obtained by standing wave tube and MTS mixture performance testing machine respectively.The noise reduction level of PERS pavement materials is quantified from the perspective of sound absorption effect and damping vibration reduction.The results show that the average sound absorption coefficients of PERS,PAC and AC are0.391,0.320 and 0.096 respectively.The dynamic modulus of PERS is also much lower than that of PAC and AC mixtures,and the PERS mixture exhibits a unique phase lag characteristic under high frequency load conditions.Secondly,based on the finite element method,the ’ tire-road-air ’ vibration / pumping noise model of the porous elastic road surface is constructed,and the distribution law of the sound field is analyzed.The vibration / pumping noise of the porous elastic road surface and the tire road noise characteristics superimposed by the two are evaluated.The results show that both vibration and pumping noise are generated in the tire-road contact area and spread outward in the form of spherical waves.Vibration noise mainly exists in the low frequency band,while pumping noise mainly appears in the high frequency band.When the initial vehicle speed is 60 km / h,compared with PAC and AC pavement,the near-field tire noise level of PERS pavement is reduced by 2.568 d B and 5.165 d B respectively,and with the increase of vehicle speed,PERS pavement performs better in noise reduction.At medium and low speeds,vibration noise accounts for a large proportion of tire road noise,but when the vehicle speed increases to 90 km / h,the proportion of pumping noise gradually exceeds that of vibration noise,which becomes the main contribution factor of tire road noise.Finally,the field noise test was carried out by paving the PERS test section,and compared with the measured values of PAC and AC pavement noise.The results show that the PERS traffic noise level is positively correlated with the vehicle speed,and the acceleration of the vehicle speed increases the proportion of high-frequency noise in traffic noise.Compared with PAC and AC pavement,the average noise reduction of PERS pavement is 2.3 d B and 4.5 d B,and the maximum noise reduction can reach 4.2 d B and7.2 d B,and PERS pavement has obvious advantages in suppressing full-band tire noise.The difference between the measured results and the predicted values of PERS is less than 1d B,which confirms the consistency of the conclusions of indoor and outdoor tests and prediction models,and verifies the excellent characteristics of PERS pavement in noise reduction.