### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 1pNS1. Active control of broadband random noise using energy density
control.

**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.