Sound Quality Design Of Exhaust Noise And Its Application In Muffler Improvement

With the rapid growth of the automobile industry,Vehicle noise control is more stringent.The traditional lower sound pressure level has been unable to meet the demand,so people’s attention began to turn to the sound quality of vehicle noise.And exhaust noise is the main noise source of vehicle noise.Improving the sound quality is very important for improving the NVH performance of the whole vehicle.In this paper,Sound Quality Design of Exhaust Noise and its application in muffler improvement.Firstly,an acoustic test of exhaust noise is carried out. And acquise the exhaust noise signal by microphone that are arranged in the exhaust port.Analyse sound quality of sound samples by using LMS Test.lab.Then the test results are analyzed under the condition of rapid acceleration.Including the sound pressure level, loudness,sharpness, roughness and fluctuation change with the speed.Secondly,combined with comprehensive evaluation of sound quality results and the composition of the sound power of the 24 Bark scales. We find out the impact of the Bark scales on the exhaust noise. To improve noise reduction in different frequency bands,The effect of the frequency change on Psycho acoustic parameters is studied.Results show that the sound quality of exhaust noise can be significantly improved as long as the sound power of the frequency band is changed;the sound quality of exhaust noise can be significantly ameliorated as long as the amount of noise reduction in 1600Hz-3200 Hz band is increased at 1000 rpm,2000rpm,3000 rpm and the amount of noise reduction in 2400Hz-4000 Hz band is increased only at5000 rpm.The main distinctions of sound energy on different frequency bands was analysed between the target muffler and improved muffler thought 1/3 octave comparative analysis.Determine the final target band to provide an important basis for the improvement of muffler.Finally,in the light of conclusion of sound quality. The noise reduction performance of the original muffler is analyzed.Starting with the insertion tubeparameters, the expansion ratio, the separator parameters and the sound absorption material,combined with the sound quality of exhaust noise,muffler improvement program is proposed.By comparing the transmission loss curve before and after the muffler improvement,We can know that the transmission loss in the medium high frequency has been evidently improved and a lot of passing frequency is eliminated.At last, the improved muffler is replaced by the original muffler,exhaust noise signal is collected under acceleration conditions.By comparing the sound quality curve before and after the muffler improvement,We can know that the sound quality of the improved muffler has been ameliorated obviously.After calculating the pressure loss of exhaust,showed that the improvement of the muffler is feasible and effective.