Narrow band active control of sound radiated from a baffled beam using local volume displacement minimization

Further development of a control technique for reduction of sound radiated from vibrating structures is presented. This control technique is based on minimization of local volume displacement, velocity, or acceleration of a vibrating structure. Multiple, single-input/single-output cancellation devices are used. Each device controller employs a motion sensor and an acoustic actuator (loudspeaker). 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. Previous work showed the successful implementation of this technique for uniformly vibrating radiators. This paper presents the development of this technique for reduction of sound radiated from a vibrating beam. A PVDF sensor was used for measurement of local volume displacement of the beam. This sensor was used in conjunction with an internal pressure sensor mounted in the loudspeaker enclosure. Sound reductions of up to 20 dB were achieved within a narrow range of vibration frequencies (centered around the first beam mode). Finally, design of a single integrated sensor is suggested for implementation of many PVDF sensors on a beam.