The gear sound was reduced by reducing the meshing transmission error to decrease the gear noise up to now. However, there is no research that considers even human aural characteristic yet. Therefore, we aim to investigate and propose the design method of the low noise gear, which considers even human aural characteristic. The proposed technique is a gear design according to controlling the frequency of the gear sound not heard on human aural. First of all, human aural characteristic was shown in a special acoustic environment in the car. In addition, the relation between the number of gear teeth and the sound pressure level of the gear sound was shown. Finally, it was clarified that this technique was effective to the design of an advantageous number of gear teeth on the aural characteristic.
