QUELLING CABIN NOISE IN TURBOPROP AIRCRAFT VIA ACTIVE CONTROL

Cabin noise in turboprop aircraft causes passenger discomfort, airfram e fatigue, and employee scheduling constraints due to OSHA standards f or exposure to high levels of noise. The noise levels in the cabins of turboprop aircraft are typically 10 to 30 decibels louder than commer cial jet noise levels. However, unlike jet noise the turboprop noise s pectrum is dominated by a few low frequency tones. Active structural a coustic control is a method in which the control inputs (used to reduc e interior noise) are applied directly to a vibrating structural acous tic system. The control concept modeled in this work is the applicatio n of in-plane force inputs to piezoceramic patches bonded to the wall of a vibrating cylinder. The goal is to determine the force inputs and locations for the piezoceramic actuators so that (1) the interior noi se is effectively damped; (2) the level of vibration of the cylinder s hell is not increased; and (3) the power requirements needed to drive the actuators are not excessive. Computational experiments for data ta ken from a computer generated model and from a laboratory test article at NASA Langley Research Center are provided.