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Active shielding based on difference potentials

Lim, H 2011, Active shielding based on difference potentials , PhD thesis, Salford : University of Salford.

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Active control of sound is a technique for altering acoustic fields to wanted ones in aimed domains by introducing controllable active secondary sound sources called controls. This thesis describes an active shielding methodology based on difference potentials for the control of noise and preservation of sound in domains. The main feature of this methodology is its ability to automatically preserve "wanted" sound within a domain while cancelling "unwanted" noise from outside the domain. This method of preservation of the wanted sounds by active shielding control is demonstrated with various broadband and realistic sound sources such as, human voice, music, etc in multiple domains in a one dimensional enclosure. Unlike many other conventional active control methods, the proposed approach does not require the explicit characterisation of the wanted sound to be preserved. The controls are designed based on the measurements of the total field on the boundaries of the shielded domain only, which is allowed to be multiply connected, and the controls are placed on the boundaries only. The cancellation and preservation can be achieved globally over a large area of the domain. The method is tested in a variety of experimental cases. The typical attenuation of the unwanted noise is found to be about 20 dB over a large area of the shielded domain and the original wanted sound field is preserved with errors of around 1 dB and less below through a broad frequency range up to 1 kHz. This thesis reports on the results of the validation for the methodology in detail, with particular emphasis on the volumetric noise cancellation and wanted sound preservation offered by the proposed methodology, which are unique features compared to other techniques available in the literature.

Item Type: Thesis (PhD)
Contributors: Lam, YLE (Supervisor)
Schools: Schools > School of Computing, Science and Engineering
Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre (SIRC)
Depositing User: Institutional Repository
Date Deposited: 03 Oct 2012 13:34
Last Modified: 30 Nov 2015 23:56

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