The noise reduction characteristics of chevron nozzles was investigated in separate flow system. All the experiments were carried out on the jet noise rig in the anechoic chamber. The effect of the structural parameters and distribution of chevron nozzles on cold jet noise reduction was explored in which shear velocity ratio was 0.92. The results show that chevron nozzles reduce jet noise at low frequencies

but increase jet noise at high frequencies. Besides

chevron nozzles has a best low-frequency noise reduction at downstream with lowest high-frequency noise penalty. The noise is decreased at the low frequencies and the peak noise reduction is 5dB when penetration angles of chevron nozzles are increased. The chevron nozzle only on fan has a good low frequency noise reduction and an ability of noise suppression at high frequencies. Although slight differences are observed with varying number of chevron

it seems that the effect is less significant than that of the penetration angles. The sound pressure level downstream is reduced significantly by chevron nozzles.