Research On Sound Insulation Properties Of Vehicle Multi-layered Materials Based On A Standing-wave Tube

With the continuous improvement of people’s living standard, vehicles are chosen bymore and more people as daily transport. In addition to the convenience, more and moreconsumers pay attention to the ride comfort of a vehicle. In order to reduce the interiornoise, vehicle acoustic engineers continue to carry out new designs of muffler materialsand its multi-layered structure and new researches of new method and equipment ofacoustic materials test. In this thesis, based on standing wave tube system, measurement oftransmission loss of multi-layered samples which made of steel panel of vehicle bonnetand soft material of inner garnish will be researched.First, sound insulation properties of vehicle flexible interior materials are analyzedand a transfer matrix is deduced based on standing wave tube testing theory. The originalsound pressure signal is processed by Matlab, insulation characteristic curve of variousmaterial samples can be derived combined with the above transfer matrix formula. Thesound insulation characteristic of multi-layered can be predicted based on the transfermatrix of multi-layered material measured with standing wave tube. The predicted resultsare consistent with the experiment results. For the steel panel, the plate vibration should beconsidered when the transmission loss is measured because of the impact of physicalattributes. Based on the theory of plate vibration and the reduction of the sound insulationperformance due to the greatly enhancement of sound radiation ability of panel, the criticalfrequency of the plate and consistent effect on sound insulation performance are discussedin a fixed frequency band. According to the continuous sound pressure and speed in theincident surface and transmission surface and the use of Euler-Bernoulli Formula, thetransfer matrix of single-layered steel panel can be deduced.At the end of this thesis, different types of steel panel plus flexible material are chosento be studied. Compared with the measurement values, the prediction results oftransmission loss are very close to the test results. Thus, this forecasting method discussedin this thesis is accurate and feasible. At the same time, the type of the same steel panel plus various flexible materials is chosen to be studied in a specific frequency band, theimpact of different flexible materials on multi-layered structure is discussed.