Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Active noise reduction (ANR) is a method of cancelling acoustic noise in a defined enclosure.
Two methods exist to implement ANR, they are the analog feedback method and the digital
feedforward method. Commercial ANR systems employing feedback methods have been around
since the 1980's. Feedforward methods have however only become practically implemental with
the age of fast real time digital signal processing. In current systems, feedback ANR is used to
attenuate broadband noise whilst feedforward methods are used to attenuate narrow band or
tonal noise [2].
This thesis investigates feedforward ANR to cancel broadband acoustic noise in aircraft
headsets. Different adaptive filters, optimal configuration of adaptive filters and practical
limitations to broadband attenuation for headsets are addressed.
Results from this thesis show that at least 10dS noise energy attenuation is attainable over a
bandwidth of 2.5kHz. A number of areas for further research are also identified. / AFRIKAANSE OPSOMMING: Aktiewe geraas beheer (AGS) is 'n metode om akoestiese geraas te kanselleer in 'n
gedefinieerde omgewing. Twee metodes bestaan om AGS te implementeer. Hulle is die
analoog terugvoer en digitale vorentoevoer metode. Kommersiële AGS wat die terugvoer
metode gebruik is al in gebruik van die 1980's. Vorentoevoer metodes is egter eers sedert
vinnige intydse digitale sein prosessering moontlik. In huidige stelsels word terugvoer AGS
gebruik vir die attenuasie van wyeband geraas terwyl vorentoevoer metodes gebruik word om
nouband of enkel toon geraas te kanselleer [2].
Die tesis ondersoek vorentoevoer AGS om wyeband akoestiese geraas te kanselleer in vliegtuig
kopstukke. Verskillende aanpasbare filters, optimale opstelling van aanpasbare filters en
praktiese beperkings tot wyeband attenuasie vir kopstukke word ondersoek.
Resultate van die tesis wys dat ten minste 10dS geraas energie attenuasie behaal kan word oor
'n bandwydte van 2.5kHz. 'n Aantal areas vir verder navorsing is ook geïdentifiseer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49761 |
| Date | 12 1900 |
| Creators | Smith, Corne J. |
| Contributors | Lourens, J. G., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 1 v. (various foliations) : ill. |
| Rights | Stellenbosch University |
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