三通管路管壁声传递损失测试方法

针对汽车进气系统三通管路的特点,提出了多通管路的管壁传递损失测试方法。并以某车型的双涡轮增压发动机进气三通管道为例,采用该方法评价其用塑料代替铝后的声学性能,主要以声传递损失来评价涡轮增压器噪声通过三通连接管路管壁的辐射和透射特性。测试过程中,三通管道的两个连接涡轮增压器端口分别用声源两次发声,靠近进气歧管端口采用两种不同反射末端,然后在每段管路布置两个压力场扬声器进行测试,并基于平面波分离入射波和反射波,同时在三通管道外用声功率半球面十点分布法自由场扬声器测试,经过3次测量来计算管道管壁的声传递损失。由于声传递损失是管道本身特性决定,所以该测试方法能够准确找出塑料件和金属件在不同频率的声学特性差异。而后,在声传递损失测试结果的基础上,结合近场声全息方法和波束形成原理进行声源识别,可知该三通管路材质改为塑料后主要噪声来自焊缝薄弱处的中高频透射声和管壁结构的低频辐射声。

Duct wall transmission loss test method of three channels

Multi-channel duct wall transmission loss test method is researched. Vehicle twin turbo engine multi-channels duct sound property is tested including plastics duct and aluminum duct. Duct wall natural sound property judgement uses transmission loss, two sound sources are used in the turbo engine ducts two inlet pipes and two different reflection terminal condition are used in the outlet pipe; each pipe uses two pressure microphones to get inject and reflect wave based on plane wave, ten free field microphones are ranged as hemisphere sound power test position outside the duct, three times tests with different duct sound source or terminal are done to calculate the transmission loss. Transmission less shows the natural property of duct wall and clearly identify the difference between plastics and metal duct on frequency domain. Near field acoustical holography and beamforming are used to find the sound source of engine duct, plastics duct major noise comes from welding area for entrant sound in high frequency range and duct structure sound radiation in low frequency range.