Acoustic Devices for the Active & Passive Control of Sound in a Payload Compartment

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dc.contributor.advisor Carneal, James P. en_US
dc.contributor.advisor Johnson, Marty E. en_US
dc.contributor.advisor Fuller, Chris R. en_US
dc.contributor.author Sacarcelik, Ozer en_US
dc.date.accessioned 2011-08-06T16:01:37Z
dc.date.available 2011-08-06T16:01:37Z
dc.date.issued 2004-05-05 en_US
dc.identifier.other etd-05242004-160125 en_US
dc.identifier.uri http://hdl.handle.net/10919/9950
dc.description.abstract The work presented in this thesis can be divided into two main subjects. First, lightweight designs for acoustic devices such as Helmholtz resonators and loudspeakers used for noise control in rocket payload compartments are developed. Second, active control using a hybrid control system (with structural and acoustic actuators) was tested experimentally. Due to the weight limitations for this application, Helmholtz resonators and loudspeakers are re-designed in order to reduce the device weight as much as possible while maintaining performance. For Helmholtz resonators, this is done by modeling the resonator for different structural shapes, wall materials and wall thicknesses using a finite element analysis software. The final design is then compared to the rigid resonators and is shown to perform effectively. These designs are then successfully applied to the full-scale fairing at Boeing facilities. In order to design a lightweight loudspeaker, a comparative approach was used. A standard 12" loudspeaker is taken as the reference loudspeaker and weight reduction solutions are applied to it while maintaining performance. The loudspeaker is characterized using mechanical, electrical and acoustical theories, and an optimization process is applied in order to minimize a defined cost function, which was taken as the total sound pressure output over a targeted frequency range per mass of the actuator. The results are used to build a lightweight loudspeaker together with a lightweight box, and the new designs are tested for comparison with the reference loudspeaker and shown to increase performance by 1.7 dB over 60-200 Hz band while reducing the mass by 78%. The second part of this thesis investigates the performance of a hybrid active control treatment featuring distributed vibration absorbers (DAVAs) and loudspeakers applied on a scale payload fairing. Several aspects such as causality, reference signals, and maximum controllable levels of this feedforward control scheme are the subjects of analyses. The results show that this active control approach can achieve significant amount of interior noise attenuation, and the total actuator weight required to control an external level of 138 dB can be reduced to 9.2kg using lightweight loudspeakers. However, it is shown that the attenuation levels can still be improved further by actuator positioning that gives more effective coupling of the actuators with the structural and acoustic modes and by using multiple references for the control system. en_US
dc.format.medium ETD en_US
dc.publisher Virginia Tech en_US
dc.relation.haspart OzerSacarcelik_thesis_revised.pdf en_US
dc.rights The authors of the theses and dissertations are the copyright owners. Virginia Tech's Digital Library and Archives has their permission to store and provide access to these works. en_US
dc.source.uri http://scholar.lib.vt.edu/theses/available/etd-05242004-160125 en_US
dc.subject active noise control en_US
dc.subject loudspeaker en_US
dc.subject Helmholtz resonator en_US
dc.title Acoustic Devices for the Active & Passive Control of Sound in a Payload Compartment en_US
dc.type Thesis en_US
dc.contributor.department Mechanical Engineering en_US
dc.description.degree MS en_US

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