Narrow-band and broadband active control in an enclosure using energy density sensors

Abstract

An active control system has been constructed based on the minimization of the energy density at discrete points within an enclosure. Though most control systems for use in enclosures are based on squared pressure as a cost function, a system based on energy density is more capable of sensing modes contributing to the acoustic field. The enclosure used is lightly damped and measures 1.5×2.4×1.9 m. A measurement system within the enclosure is capable of spatially sampling the pressure field and decomposing the field into complex modal amplitudes, which yield insight into the control phenomena. The control system can use squared pressure as well as energy density as a cost function for comparisons of the two methods. The squared pressure and energy density control are consistent with predictions of active control performance in the case of single-frequency multiple sensor/source configurations. Global control of up to 18 dB is achieved. Broadband control results using a single sensor and control source are also presented.

Active control of energy density in a one-dimensional waveguide: A cautionary note (L)

“…[10][11][12][13][14][15][16][17][18][19] Acoustic energy density, defined as the sum of the acoustic potential and kinetic energy densities at a point, is commonly estimated using the two-microphone method 1 and is given by ͑see the Appendix͒…”