Micro Cooling Fan loud what is the reason?

Under normal circumstances, "Micro Cooling Fan" The higher the rotational speed, the noise will be greater. If the non-prolonged abnormal noise, then that fan itself is not the problem. The reason that the fan noise after another, from the temperature-controlled cooling. When the CPU tasking frequently, the temperature will gradually, "Micro Cooling Fan" will take the initiative to enhance the speed, and thus play a cooling effect. The strength of the human ear to hear the sound, actually sounds with frequency vary, for example, when 1000Hz particularly sensitive ear, so the two different frequencies identical sound pressure will be so great frequency of 1000Hz its volume. The so-called "Micro Cooling Fan" the difference between noise and music just sounds comfortable or not, and no two in sonic terms.