Kyle Martini
John E. Cole, III
Cambridge Acoust. Assoc., Inc., 200 Boston Ave., Ste. 2500, Medford, MA 02155
Enclosures are used to control the noise radiated by industrial machines such as pumps and internal combustion engines. The passive transmission loss of enclosures at low frequency can yield negative insertion loss occurring at resonances of the enclosure panels backed by the internal air cavity. Active noise control provides a means to enhance low frequency performance by eliminating enclosure resonances. Because it is not feasible to use far-field acoustic measurements for control, the surface vibrational response of the enclosure is used to control the noise radiated. Enclosure response characteristics are obtained from a finite element model of the three-dimensional enclosure. A vibrated surface within the enclosure is used to represent a machine. When coupled with a boundary element formulation of the Helmholtz integral equation, the model calculates the surface response of the enclosure as well as the far-field radiated pressure. Transfer functions between the excitation and both surface and far-field responses are obtained. Results of the finite element model are compared with analytical models of enclosure performance. [Work supported by the National Science Foundation.]