Active control of sound transmission

Abstract

This thesis is concerned with the active control of sound transmission through structures. A particular emphasis of the work is the reduction of the complexity of the controller required to achieve good attenuations by the use of distributed sensors and actuators.

The theory of radiation modes, which is a technique for decomposing the velocity profile of a radiator into a set of independently radiating velocity distributions, is presented first. The first radiation mode of a structure is shown to be the dominant radiator of sound at low frequencies and to have an amplitude which is well approximated by the volume velocity of the structure. The cancellation of volume velocity is suggested as a good strategy for reducing the sound power radiation at low frequencies. Radiation mode theory is more generally shown to be a convenient method for determining the complexity of the control system required to reduce the sound radiation from a structure.

The design of a volume velocity sensor for beams and rectangular plates with fixed boundary conditions is suggested. This design uses a pattern of quadratically shaped strips etched into the electrode of a sheet of PVDF (piezoelectric) film.

The strategy of volume velocity cancellation is initially investigated using a computer simulation and is shown to perform well at low frequencies, when compared with the optimal strategy of sound power minimization. In controlling sound radiation a compact secondary actuator can increase the average velocity of the panel and thus increases the pressure generated close to the panel. The use of the matched actuator/sensor pair, consisting of a volume velocity sensor and a uniform-force actuator, is shown to reduce control spillover and thus avoid increasing the plate velocity when controlling sound radiation. The transfer response between such a matched actuator and sensor is also shown to be minimum phase, which has important implications for the performance of the control system. A distributed sensor and actuator would also be beneficial in the active control of sound transmission into a cylinder, which is also briefly examined.

More information

Identifiers

Catalogue record

Export record

ASCII CitationAtomBibTeXData Cite XMLDublin CoreDublin CoreEP3 XMLEndNoteHTML CitationHTML CitationHTML ListJSONMETSMODSMPEG-21 DIDLOpenURL ContextObjectOpenURL ContextObject in SpanRDF+N-TriplesRDF+N3RDF+XMLRIOXX2 XMLReferReference ManagerSimple Metadata