Abstract:

The active control of sound radiated from structures using two near-field sensing strategies is investigated theoretically. The two sensing strategies involve minimizing the sum of the sound intensities and minimizing the sum of the squared sound pressures in the acoustic field close to the surface of a rectangular panel. A new quadratic expression is derived for the minimization of the sum of the sound intensities in the near-field. The formulation is expressed in terms of the primary sound field and the measured or calculated transfer functions from the control inputs to the error sensor outputs. Thus, the expression given here can be used to solve any complex problem where the control source to error sensor transfer functions and primary sound field pressures can be determined. In this example, a flat panel is modeled with harmonic point force excitation and several point force control sources. To compare the control performance achieved by the proposed near-field sensing strategies, the radiated sound field is minimized in the near-field, and then the control results are evaluated in the far-field for each test case.