Modification of impact sound by adjusting the excitation input for comfortable design of punch press machine sound

The effectiveness of adjusting the excitation input as a method for modifying impact sound was investigated. The radiation from the impact can be described using a convolution of an impulse response function for a vibro-acoustic system and the corresponding impact excitation function. Therefore, the radiated sound can be changed by modifying both the impact excitation function and the structural response. Excitation with complicate shapes of input which is required to make an arbitrary shape of wave form, such as selective excitation or rejection of a specific frequency component, is not easy for manually operated traditional system. However, the modification of excitation input is useful for the automated system with an electrically controlled impactor, such as a servo-motor. As a practical application, a punching process of a punch press machine was designed to not only reduce the overall sound pressure level but also improve the perceived sound quality. Sound from a punch press can be improved by dividing the punching process into several steps with different stroke speeds without substantially reducing the cutting surface quality.