A Study On Low Frequency Noise Of Vehicle Exhaust Muffler

With the social progress, people’s awareness of environmental protection is stronger and stronger. As a major part of environmental pollution, noise pollution has got more and more attentions from society. With the gradual increase of the number of vehicles, the traffic noise generated by vehicles has become the main source of urban noise, and low frequency noise as the most important but also most difficult to be eliminated is more and more extensively researched. Low frequency noise will not only seriously affect people’s lives and works, but also affect people’s healths. Thus reducing the vehicle exhaust low frequency noise has become an important part of field of automotive research.With the increasing of the number of vehicles, the traffic noise produced by the vehicles has become the main source of the city noise. The low-frequency noise is the uppermost but also the most difficult to eliminate of the vehicle noise, and now it’s researched more and more extensive. Low-frequency noise can not only affect people’s health, but also have important influence on people’s subjective perception characteristics. As the main power source of the vehicle, the engine is also the main noise source of the vehicle. The most part of the engine noise is spread through exhaust system, so controlling exhaust low-frequency noise effectively and reducing the low-frequency noise largely are more and more important. Thus reducing vehicle exhaust low-frequency noise has become an important content in the research field of the vehicle.In this paper the method of combining software simulation and experimental testing is used to research the low frequency noise control of vehicle exhaust muffler. The method of reducing low frequency noise is concluded and applied to the positive muffler design. Then the accuracy of the conclusion is verified.Firstly, the GT-Power software is used to calculate the transmission loss of several main kinds of mufflers by changing the parameters of their structures. Then the factors of increasing low frequency noise deadening capacity are identified. Combined with theoretical analysis, the conclusion of reducing low frequency noise is identified.Secondly, after the experimental tests of the exhaust noise of a cross country vehicle and the exhaust system simulation in GT-Power, combined with the test results and the simulation results, it’s explained that the exhaust noise in67Hz is oversize.Finally, based on the conclusion of reducing low frequency noise and combined with simulation and calculation results in GT-Power software, a new muffler program is designed to reducing67Hz low frequency noise. Then the sample mufflers are manufactured and tested. The result shows that the noise elimination performance of the new program mufflers is satisfactory. It’s proved that the method of reducing low frequency noise is feasible.