In the summer my CPU fan sound screams very loud, but after turning on the air conditioning will not make a loud sound, may I ask how to solve such a problem?

The CPU fan sounds loud because the temperature is high, resulting in the internal temperature of the case is also higher, the CPU cooling slow, the temperature sensor will automatically adjust the fan speed, increase the air volume to the radiator, so the resulting noise. The air conditioner reduces the room temperature, which helps to reduce the internal temperature of the case.

You can replace the CPU cooler with a heat-pipe cooler that dissipates heat more efficiently, and a cooling fan that uses a large diameter and low RPM.