*** ABSTRACT 9660605 Sofge This Small Business Innovation Research Phase I project will develop and test a new approach to active interior noise control in a three-dimensional enclosure. The new thrust in the proposed research is a digital adaptive system that makes use of both analyses and directly measured data from a three-dimensional enclosure to card out active noise control by using smart materials located on flexible boundaries of the enclosure. The system is intended to track the changes in the acoustic information due to movement, changes in open apertures, etc. and carry out on-line minimization to realize the desired acoustic performance. Unlike most methods that assume that the acoustic field inside the enclosure can be modeled by using standing waves, the proposed method is designed to accommodate diffuse sound fields in the enclosure. Furthermore, the noise is not assumed to be harmonic and nonperiodic sound fields are to be considered. The neural network based filter proposed herein can make use of analytical and experimental data to assign initial weights that are to be adapted to carry out (locally) on-line minimization of sound pressure in the enclosure. Noise reduction in aircraft is a subject of serious commercial concern in the industry. The techniques developed in this effort will be widely applicable to noise reduction in rotorcraft cabins of commercial helicopters, and may be adapted for use in commercial airline cockpits, as well as in factory settings and other vibration critical manufacturing environments. ***
