Thesis-2008-Godbald.pdf (25.15 MB)
Investigating broadband acoustic adsorption using rapid manufacturing
thesis
posted on 2011-02-17, 11:53 authored by Oliver GodboldThe reduction of nuisance noise and the removal of unwanted sound modes within a room or component enclosure-area ccomplished through the use of acoustic absorbers. Sound absorption can be achieved through conversion of the kinetic energy associated with pressure waves, into heat energy via viscous dissipation. This occurs within open porous materials, or by utilising resonant effects produced using simple cavity and
orifice configurations. The manufacture of traditional porous and resonant absorbers
is commonly realised using basic manufacturing techniques. These techniques restrict
the geometry of a given resonant construction, and limit the configuration of porous
absorbers. The aim of this work is to exploit new and emerging capabilities of Rapid Manufacturing (RM) to produce components with geometrical freedom, and apply it to the development of broadband acoustic absorption. New and novel absorber geometric configurations are identified and their absorption performance is determined. The capabilities and limitations of RM processes in reproducing these configurations are demonstrated. The geometric configuration of RM resonant absorbers is investigated. Cavity
modifications aimed at damping the resonant effect by restricting the motion of cavity
air, and adding increased viscous resistance are explored. Modifications relating to cavity shape, the addition of internal perforations and increased cavity surface area have all been shown to add acoustic resistance, thereby increasing the bandwidth of
absorption. Decreasing the hydraulic radius of the cavity cross section and reducing
internal feature dimensions provide improved resistance over conventional
configurations.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© Oliver GodboldPublication date
2008Notes
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.497221Language
- en