Title page for ETD etd-11012008-063701
|Type of Document
||Mahnken, Brian W.
||Active structural acoustic control of aircraft interior flow noise via the use of active trim panels
||Master of Science
|Fuller, Christopher R.
|Burdisso, Ricardo A.
|Cudney, Harley H.
|Date of Defense
Modem jet aircraft interior noise can be categorized into two main types: tonal noise
caused by engine imbalance or blade passage, and mid frequency broadband noise
resulting from turbulent flow. This project addresses aircraft interior flow noise caused by
a flow separation over the crown of the aircraft. The noise control approach is to mount
piezoelectric actuators to the aircraft interior cockpit crown trim panel and use them to
actively control aircraft interior noise with feed-forward adaptive LMS control algorithms.
The experiments were performed on a Cessna Citation III fuselage with the production
crown interior trim panel in place. Flow noise was simulated by three speakers mounted
above the crown of the aircraft producing random noise with a frequency range of 500-1000 Hz. Several piezoelectric (PZT) actuators were mounted on the interior crown trim
panel as control outputs. Sixteen microphones served as error/global attenuation sensors.
Microphones and PZTs were selected from off-line optimizations. The control reference
signal was obtained from either an accelerometer mounted on the skin of the aircraft or
from the signal generator itself. Control was executed on a personal computer digital
signal processing. Single frequency control experiments were performed to judge the
feasibility of control. The main broadband tests were performed with a variety of
controller configurations. The results using the active panel are compared with more
traditional acoustic control utilizing speakers as control actuators instead of PZT's. The
project concludes that a 2 dB reduction over the frequency range is obtainable at the
pilot's ears in a 2I20 configuration with an accelerometer reference signal. Acausality and
slow controller speeds were found to be the main causes which limit further reduction.
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