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2.There is a current sound when the notebook connects the projector and the power amplifier at the same time, the notebook is not connected to the power adapter, and there also be alternating sound with its own battery, but as long as the projector is unplugged, there be no current sound. 4.Computer connected to headphones is normal, connected to the mixer or stereo has noise. 3.When we start the car engine, we install the horn of the car power amplifier, or the active subwoofer produce current noise, noise, etc., and the noise of some models increase with the increase of the throttle. 1.Pickup to DVR stereo, there is a loud buzzing current sound. 5.When the computer is connected to the projection, it is normal to use headphones, but there is noise as soon as the mixer is connected.