Abstract: This paper presented the background noise measurement technology scheme of 0.55m×0.4m aeroacoustic pilot wind tunnel newly designed in China.It made some comparative tests and data analysis of condenser microphone,piezoresistive transducer,prepolarized microphone,externally polarized microphone,free-field microphone,pressure-field microphone,sensor installing methods and acoustic frequency spectrum algorithm.According to the obtained data,some measures were taken to optimize the noise reduction performance of the wind tunnel.It showed that condenser microphone is more accurate than piezoresistive transducer used for background noise measurement.After correction,pressure-field microphone and free-field microphone could be replaced by each other.Spectrum linear average algorithm should be used to calculate the muffler noise transmission loss for the sake of repetitive precision.The conclusion is helpful for background noise measurement of low speed aeroacoustic wind tunnel.