| As expects sales continue to increase, the noise of the car is driving personnel, and by the road side a lot of complaints from residents, manufacturers are also very concerned about, and indoor acoustics lab evaluation and research and development car acoustic quality is necessary means, a lot of construction manufacturers and research institutions at home and abroad. Auto transmission NVH test bench is an objective evaluation of vehicle power transmission mechanism and assembly of key equipment. The device’s power often require external acoustic experiment in the outside, through the shaft power is passed to the acoustics of the assembly being tested in the laboratory, it also will be introduced to the outdoor noise acoustic experiment indoor, so that greatly influence the assembly test results to be tested. Acoustic experiments indoor and outdoor, therefore, need to have sound insulation and noise reduction, sound insulation structure to implement in order to meet the indoor acoustic measurement and related standards at home and abroad.Research of this paper is commissioned this research comes from a research institutions set up auto transmission NVH test bench and develop a noise enclosures;. This paper according to the measurement noise in the transmission test bench for the input conditions, based on one dimensional plane wave theory, the panel resonance structure is simplified to quality-spring resonance system, establish its inherent frequency calculation method, the design of broadband large amount of acoustic noise enclosures;, the drive test rig noise control within the scope of the relevant standards, solved the dynamic system noise band wide value in sound insulation noise reduction of the noise of the big problems.First of all, through the analysis of the acoustic structure of existing features, based on the panel resonance sound insulation structure in low frequency narrowband has good sound absorption performance, as well as the micro hole structure have multiple audio band absorption, combination of fiber and porous foam in high frequency has a good sound absorption effect, multistage composite board resonance type acoustic structure are put forward. This paper studies the sound insulation structure of resonance plate material and thickness will effect the performance of the acoustic parameters, such as, found resonance plate thickness is thin, the farther low frequency sound absorption performance of its direction, adopt different plate in parallel resonance structure at the same time, you can get a wider frequency sound absorption effect; Found the micro-perforated sound absorption bandwidth structure can be extended in parallel. On this basis, to harshness (NVH) testing of auto transmission system to design noise enclosures;. According to the measured noise acoustic characteristics of the power system, the design has two levels of resonance plate composite structure of noise enclosures;, effectively reduce the noise elimination of indoor low-frequency noise.Secondly, based on one dimensional plane wave theory, the GT-POWER software analysis micro perforation rate, absorption material and structure’s influence on acoustic performance. Found micro perforation rate of increase has certain significance to the high frequency noise, but the low frequency sound insulation effect is not big, but in the depth of sound insulation structure is larger, can have an effect on low frequency noise; Inside and outside the room in the simulation of interlining is simplified to cavity structure, interference sound absorption structure formation, get good sound absorption effect. For the perforated pipe noise enclosures; design has a certain guiding significance. On this basis, the optimization of the structure, increased the low-frequency noise sound insulation quantity.Finally, for the validation of multi-level composite board type of resonance sound absorption structure of acoustic performance, in a semi-anechoic chamber for noise enclosures; and install noise enclosures; not installed after a series of experimental study. Through the analysis of the test results the parallel than single micro perforated panel of microperforated panel has wider bandwidth of sound absorption; Multistage composite board type of resonance sound absorption structure of sound insulation quantity is much better than a single sound absorption structure, size and structure is more compact and suitable for application in acoustic test device of sound transmission, measured pieces in the anechoic room sound field distribution as the research laid the foundation. |
