An electric-motor which uses electric energy to dry laundry in a dryer generates wind by rotating a fan. The roles of electric motor and fan are crucial for drying. To reduce the noises or vibration, their performances should be improved. However, it requires a relatively high cost to redesign them. In this case, redesigning the fan case rather than the motor or the fan would be easier and cheaper. This paper is to apply Taguchi dynamic characteristic concept with the ideal function of energy conversion to redesign the fan case. Not only the increase of the wind power but also the decrease of noise, vibration and the other side effects are resulted. †