Young C. Park
Scott D. Sommerfeldt
Appl. Res. Lab. and Graduate Program in Acoust., Penn State Univ., P.O. Box 30, State College, PA 16804
Previous work on active noise control in enclosures has indicated that one can often achieve improved global attenuation of deterministic signals by minimizing the acoustic energy density, rather than the squared pressure. The purpose of this work is to present numerical results that compare the global attenuation of broadband noise achieved by minimizing energy density with the attenuation achieved by minimizing squared pressure in a one-dimensional enclosure. A theoretical approach based on the frequency domain enables one to establish the basic physical limitations of active noise control systems. However, this approach cannot necessarily be applied when controlling a broadband random noise, since it often yields optimal control solutions that are noncausal in the time domain, even though such a frequency domain approach is entirely satisfactory for deterministic signals. Analyses reported here are undertaken in the time domain in a manner that yields the form of the causally constrained optimal controller. Numerical results are presented to predict the performance of the active noise control system designed to control a broadband noise, and to indicate the improved global attenuation of broadband noise that can be achieved by minimizing energy density, rather than squared pressure.