"220V Cooling Fan" noise is usually measured in a special isolation room semi-anechoic carried compartment all the ceilings and walls are installed in each sound-absorbing material. In our special isolation room, the ambient background noise has been significantly reduced to an amount sufficient to test all products work fine noise. Traditionally, the "220V Cooling Fan" area of ??expertise is the sound pressure of the indicators to assess the value of the size of the fan noise. However, only the sound pressure data is not enough to understand the real life of human auditory perception of a particular sound, so the importance of this indicator in recent years, in the heat "220V Cooling Fan" in the field has become increasingly decline.