This thesis presents a comprehensive methodology for predicting and minimising the noise radiated from a constant speed gearbox assembly by means of attaching optimally placed stiffening ribs on the casing. The procedure involves building an FE model of the gearbox, which is updated using modal parameters extracted from a modal test. This is followed by synthesis of the required FRFs with respect to the forcing degrees-of-freedom. The forces, which are assumed to act only at the bearings are identified from these FRFs and the measured operational velocities of the casing. The identified forces are then used to excite the updated FE model to re-calculate the vibration velocities. A boundary element method is used to calculate the final radiated sound power to be compared with that measured. The same forces are used later to excite the modified gearbox casing to determine the improvement given by optimised modification. The optimisation study minimises the vibration energy of the casing in 10% bands around critical frequencies, in this case the first two harmonics of the gearmesh frequency. To allow for errors in the model, the excitation is by white noise, so as to produce wide stop bands, rather than minimising the response at particular frequencies. The vibration energy is weighted for radiation efficiency, A-weighting, and relative source strength in the bands. The final optimal stiffener layout is validated through a final vibration and acoustic calculation on the updated gearbox model using the forces identified in the earlier steps. The study of one particular gearbox concludes that i) the proposed hybrid optimisation scheme produces a theoretical effective noise reduction of 3 dBA for the total sound power. ii) Because the gearmesh harmonics were targeted, a further 5 dB improvement was effectively gained by eliminating the tonal penalty which otherwise applied. iii) From plate studies it was demonstrated that the stiffening ribs could be attached using epoxy cement (to avoid welding) and that the properties of the cemented joint could be determined by model updating after attaching one rib, so as to obtain a better prediction of the final optimised result.

Local active noise control systems aim to create zones of quiet at specific locations within a sound field. The created zones of quiet generally tend to be small, especially for higher frequencies, and are usually centred at the error sensors. For an observer to experience significant reductions in the noise, the error sensors therefore have to be placed relatively close to an observer’s ears, which is not always feasible or convenient. Virtual sensing methods have been proposed to overcome these problems that have limited the scope of successful local active noise control applications. These methods require non-intrusive sensors that are placed remotely from the desired locations of maximum attenuation. These non-intrusive sensors are used to provide an estimate of the sound pressures at these locations, which can then be minimised by a local active noise control system. This effectively moves the zones of quiet away from the physical locations of the transducers to the desired locations of maximum attenuation, such as a person’s ears. A number of virtual sensing algorithms have been proposed previously. The difference between these algorithms is the structure that is assumed to compute an estimate of the virtual error signals. The question now arises as to whether there is an optimal structure that can be used to solve the virtual sensing problem, which amounts to a linear estimation problem. It is well-known that the Kalman filter provides an optimal structure for solving such problems. An optimal solution to the virtual sensing problem is therefore derived in this thesis using Kalman filtering theory. The proposed algorithm is implemented on an acoustic duct arrangement to demonstrate its effectiveness. The presented experimental results indicate that the zone of quiet was effectively moved away from the physical sensor towards the desired location of maximum attenuation. The previously proposed virtual sensing algorithms have been developed with the aim to create zones of quiet at virtual locations that are assumed spatially fixed within the sound field. Because an observer is very likely to move their head, the desiredlocations of the zones of quiet are generally moving through the sound field rather than being spatially fixed. For effective control, a local active noise control system incorporating a virtual sensing method thus has to be able to create moving zones of quiet that track the observer’s ears. A moving virtual sensing method is therefore developed in this thesis that can be used to estimate the error signals at virtual locations that are moving through the sound field. It is shown that an optimal solution to the moving virtual sensing problem can be derived using Kalman filtering theory. A practical implementation of the developed algorithm is combined with an adaptive feedforward control algorithm and implemented on an acoustic duct arrangement. The presented experimental results illustrate that a narrowband moving zone of quiet that tracks the desired location of maximum attenuation has successfully been created. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1291123 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007.

Manchester, in the first half of the nineteenth century, held great fascination to many as an example of a town being remade and transformed by the technological developments of the Industrial Revolution. The transformations experienced included the rapid physical expansion of the town and its population and the reordering of its society from a traditional, rigid class structure, involving a powerful aristocracy and working-class citizens, to a new social hierarchy with a numerous and influential middle class—an emerging ‘urban aristocracy’ of people involved in manufacturing, commerce and other professions. As these changes took place, the rest of England (and the Western world) looked on—horrified, shocked, awed, fascinated. It was a different world, and the rapid changes taking place in society created in observers a sense of urgency in describing the effects of those changes—particularly the social problems, which had been shaped by industrial life. / A trend in describing Manchester’s residents as ‘philistines’ and the town, generally, as a ‘cultural wasteland’ took hold at this time and has been perpetuated until fairly recently. This thesis explores this trend—Manchester’s nineteenth-century image—and the impact of contemporary opinion on constructions of social hierarchies and cultural reputations. It also aims to show that there was more to Manchester’s cultural life in the nineteenth century than is widely acknowledged, either by contemporaries from the period or by some scholars today, and that the pursuit and experience of music and certain noises was genuinely wanted by the manufacturing class for a number of key reasons. / Delving further, into studies of soundscapes and ‘noise,’ it becomes ever clearer that sound, and how individuals and societies interact with it and interpret it, acts as an important—though frequently overlooked—signifier of class relations and civic identity. Finally, this thesis aims to reconstruct how Manchester sounded in three principal regions of the town to show how a study of soundscapes helps to articulate how the town was psychologically constructed in the minds of inhabitants and visitors, and how it was sensed and experienced.

Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 62-63)

Thesis (Ph. D.)--University of Adelaide, Dept. of Mechanical Engineering, 1984. / A supplement to this thesis containing tabulations of all acoustic data is available from the Department of Mechanical Engineering, University of Adelaide. Includes bibliographical references (leaves 109-113).

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains iii, 44 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 42-44).

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1986. / Includes bibliographical references (leaves 221-232).

Thesis (M.S.) in Electrical Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 68-69).

Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999. / Copies of author's previously published articles inserted. One computer disc (CD-ROM) in plastic jacket pasted onto back cover. Bibliography: leaves 319-339. Also available electronically.

Thesis (Ph.D.) Dept. of Mechanical Engineering, University of Adelaide, 1979. / Typescript (photocopy).