Near-field sensing strategies for the active control of the sound radiatedfrom a plate

When designing an active control system to globally control the far-field s ound radiation from a vibrating surface, a challenging problem is to proper ly define the near-field acoustic sensing strategy and the type of cost fun ction to be minimized by the controller. The strategy of sensing and minimi zing the near-field active intensity at discrete locations in the active co ntrol of free field radiation from a vibrating plate is investigated in thi s paper. The optimal minimization of the sum of the near-field, normal acti ve sound intensities at the error sensor locations using acoustic control s ources is derived for this problem, and the results obtained are compared t o the minimization of the sum of the near-field squared pressures. Some of the difficulties associated with sound intensity minimization are pointed o ut. (C) 1999 Acoustical Society of America. [S0001-4966(99)05211-X].