Noise reduction laws for turbofan engines require effective configurations to reduce jet engine noise. Lobed mixers are known to be effective for noise reduction in high bypass ratio turbofan engines. In this study, a mixture of hot and cold flow is simulated in a lobed mixer for a high bypass ratio turbofan engine. Navier-Stokes equations are considered three-dimensional, compressible, steady, and turbulent. To solve the turbulent flow, the turbulent model has been used; besides, to investigate the acoustic power, the Broadband noise source model was applied. In this research, first, the simulation method was validated and the results were compared with the experimental data of previous studies. Then, the impact of the lobed mixer was investigated on mixing hot and cold flow and noise reduction in a high-bypass ratio turbofan engine. The results of this study show that the maximum acoustic power was obtained at about 72 dB at a distance of 14 meters from the nozzle, decreasing by moving away from the engine nozzle; also, the maximum amount of acoustic power in the central body at nozzle exit has decreased from about 90 dB to 72 dB. The maximum acoustic power was observed at about 95 dB on the mixer surface next to the central body flow. Finally, we can conclude that a mixture of flow reduces the acoustic power and improves its uniformity at the nozzle exit while increasing the acoustic power near the central body.