Most computers will have buzzing AC noise when they are plugged into the projector. The reason is difficult to analyze. Is there ground wire interference? Neutral interference? Projector bulb current interference? Voltage difference? Anyway, the reason is hard to judge. First, try to disconnect the ground wire of the computer power supply. The noise disappears and the interference comes from the ground wire. If the noise still exists, it is recommended to disconnect the cable from the projector first. If the noise disappears, try to disconnect the ground wire of the projector. If the noise still exists, it is recommended to add an audio isolation transformer or an audio noise canceller.