Date of Award
Doctor of Philosophy
Mechanical and Aeronautical Engineering
Dr. James Kamman
Dr. Koorosh Naghshineh
Dr. Dennis J. VandenBrink
Dr. Hossein Mousavinezhad
An active noise control apparatus is developed. The device reduces the sound radiated from a vibrating clamped beam. The attenuation of the sound field is obtained through minimization of local volume displacements of the vibrating beam. Two single-input/single-output cancellation devices are used. Each device employs a motion sensor and an acoustic actuator. The actuator is a loudspeaker equipped with a pressure sensor to detect its volume displacement. The motion sensor signal is related to the local volume displacement of the structure which is then reduced by a loudspeaker driven with an equal but opposing volume displacement. The volume displacement sensors are developed and fabricated using Polyvinylidene Fluoride (PVDF). They measure the local volume displacements of the vibrating beam. The pressure sensor is mounted in the loudspeaker enclosure. It provides the feedback signal for the loudspeaker volume displacement control.
Previous work showed the successful implementation of this technique for uniformly vibrating radiators. This thesis presents the development of this technique for the reduction of sound radiated from a vibrating beam. First, a numerical local volume displacement cancellation experiment is performed using several loudspeakers, each canceling the volume displacement of a section of the beam. The finite element method is used to calculate the velocity distribution of the vibrating beam. A discretized form of the Rayleigh integral is then used to find the sound pressure and the sound power radiated before and after cancellation.
Second, the numerical results are verified by laboratory experiments using a beam divided into two sections. Two motion sensors for the beam and one pressure sensor for each loudspeaker are fabricated and thoroughly checked. The cancellation experiment is then performed on a broadband random noise using two independent Proportional-Derivative (PD) controllers.
Zahui, Marcellin, "Active Local Volume Displacement Cancellation of a Vibrating Baffled Beam" (1999). Dissertations. 1540.