Active Control of Impact Sound

Impacts are an important noise source of today's society. From a control standpoint, solutions to problems related to impacts are commonly based on passive methods. In this paper, an active method to control the radiated sound from a sphere impacting a simply supported plate attached to an infinite baffle is proposed. The contact force between sphere and plate is modeled by Hertzian contact, this force is then convoluted with the plate's impulse response. From this, the radiated sound field is calculated by the Rayleigh integral in the time domain. In a following step, an active force is used to act on the plate with the purpose of minimizing the radiated sound power. This control force is estimated using a method based on the LMS algorithm formulated in the time-domain. For different positions of the impact between the sphere and the plate, the position of the active force is varied and for each case, the LMS algorithm obtains the optimal time record of the force. For non-trivial cases, where the acting force is not in the same position as the impact, examples of preliminary results present reductions of up to 6 dB in the simulations of the radiated sound power.