Research And Analysis Of Acoustic Coupling Of Vehicle Muffler

With the increasing of vehicle population in China, noise pollution problem has become more seriously, attention to noise issues are becoming more highly than before. Engine noise is the main source of noise pollution, Engine vibration and noise reduction has been a hot academic research.Now, the internal combustion engine exhaust noise control measures are mainly two aspects.First, from the propagation mechanism of noise sources start to control the noise source. Second, to install exhaust muffler in the exhaust port, this method is simple and effective, so become the most widely used method at home and abroad.In the design phase, according to the design data to predict performance muffler, which has important guiding significance for the optimization of the design phase.Research shows that between actual performance and design phase conditions muffler theoretical simulation data has some bias. Scholars believe that these deviations may be associated with acoustic coupling, the actual testing environment, data measurement and data processing errors, acoustic coupling is one of the main factors.The actual calculation of muffler start from the basic equation, the muffler wall made of rigid handle, and does not consider the flow rate of the medium.But the result of this calculation is generally with the actual situation is obviously different, there is a big difference between the muffler performance and theoretical simulation.When the need for accurate calculation of attenuation performance and considering the influence of acoustic solid coupling, wall vibration will serve as boundary condition for acoustic equation, increased the difficulty of solving differential equation.For solving the acoustic coupling problems, generally using the finite element method, wall vibration will serve as boundary condition, boundary vibration change into the sound pressure wave.Correction of acoustic stiffness matrix by using the boundary vibration, Solving effect of sound structure coupling.Acoustic performance computing are generally starting from the basic equations of acoustics, derive acoustic performance of muffler considering acoustic coupling, And calculated using acoustic software. Study structure, thickness, material, and constraints effect acoustic structure coupling. Starting from the modal concept, analyzes the relationship between structural vibration and internal pressure, structure vibration and sound pressure to change the acoustic characteristics of mufflers.Get in some frequency band is not negligible acoustic solid coupling, In the design phase to analyze it sound coupling,and give advice to improve the acoustic structure coupling.