220V Cooling Fan sound principles

Allowed to produce electricity for air flow acting "220V Cooling Fan", with air blowing produces mechanical rotation is called turbines, water turbines why some fans called loud, why some fan sound small, the same fan Why the big noise generation fighter, and "220V Cooling Fan" does not have the sound. The sound is acoustic effect to the results of your eardrum, a fan in what way, sound waves generated to get your eardrums sound waves is a certain frequency the vibration generated in the air, your "220V Cooling Fan" is what produced the band's sound, the sound of low frequency to high frequency hum harsh, loudness, expressed in decibels, represents the intensity of the sound. in the end how much sound.