A COMPARISON OF NEAR-FIELD ACOUSTIC ERROR SENSING STRATEGIES FOR THE ACTIVE CONTROL OF HARMONIC FREE-FIELD SOUND RADIATION

A theoretical comparison of a number of near-field acoustic error sens ing strategies is undertaken for active control of harmonic free-field sound radiation. Error sensing strategies investigated include the mi nimization of acoustic potential energy density, acoustic kinetic ener gy density, total acoustic energy density and mean active sound intens ity at a point and the minimization of the sum of each cost function a t a number of points in the near field. The error sensing strategies a re analyzed for harmonic sound fields radiated by a monopole primary s ource and a dipole-like pair of primary sources. The control source is a monopole radiating at the same frequency and the criterion used to assess the error sensing strategies is the minimization of the total r adiated acoustic power. It was found that the most appropriate near-fi eld acoustic error sensing strategy for the active control of harmonic free-field sound radiation is minimizing the sum of the weighted mean active intensity in the direction normal to the surface surrounding a ll the primary and control sources. (C) 1998 Academic Press.