Abstract
It is known that a rapid change of rotation sometimes results in an unpleasant or unnatural noise from the cooling fans affixed to the rotors of the alternator. This noise is often referred to by the imitated or onomatopoeic expression "myah" in Japanese. It was found that the primary cause of this "myah" sound is the frequency change at the maximum 1/3-octave-band noise level, and that sound quality can be improved by controlling this frequency within a specific range.
