At present, the motherboard of the new machine can adjust the voltage of the cooling fan according to the use of hardware such as CUP by software in the computer. The fan speed is high when the computer is busy and low when the computer is idle. When you first start up, your computer is running at full load due to system startup, software loading and other factors (which is also the reason why you feel slow when you start up), so the fan speed reaches the highest, and some fans with low quality will make noise when the lubricating oil is not fully lubricated. After the machine is started, it enters a relatively idle state. On the one hand, it reduces the rotation speed of the fan, on the other hand, it is basically fully lubricated, so the noise is small. Restarting after antivirus is a hot start. The hardware of the machine is not powered on at all, but the operating system will restart. From the hardware point of view, your machine is still in a normal boot state, and you won't hear abnormal sounds again. If you turn it off and turn it on again, the abnormal sound should not be too obvious in a short time, but it will be obvious when the interval is long.

Solution: the fundamental solution is to see which fan makes abnormal noise and change it-no matter how high the speed of a high-quality fan is, there will be no big abnormal noise; Another idea is to reduce the burden of machine startup, slim down the operating system, reduce unnecessary startup items, and choose antivirus software that takes up less machine resources. In this way, your machine can be started lightly and this problem will be alleviated.