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Modelling, measurement and optimization of passive and active custom-made hearing protectors

Annelies Bockstael UGent (2010)
abstract
In industry, hearing protectors are often implemented to prevent noise-induced hearing loss, but the use of protectors at the workfloor might substantially vary from laboratory conditions. Therefore it seems advisable to also verify the attenuation in situ, for instance with the MIRE (microphone in real ear) approach. The first aim of this research project is to investigate the implementation of the MIRE technique for custom-made hearing protectors designed with a test bore. In this channel, a MIRE measurement microphone can be slided to measure the sound pressure in the ear canal. This setup allows quick and stable measurements, but the issue is the difference in sound levels between the microphone and the eardrum. This relationship, henceforth called transfer function, is studied in different ways. First, the transfer functions are registered with a head-and-torso-simulator (HATS) and simulated with numerical FDTD (finite-difference time-domain) models. They appear to be stable, reproducible and depend on clearly distinguishable characteristics of earplug and ear canal. In the second stage, transfer functions are assessed for human subjects in a similar way. They vary substantially with respect to the exact configuration in function of the frequency, but this can be predicted with individualized FDTD simulations. Based on these findings, a filter approach is developed to allow implementation in practice. The second aim is addressing verbal communication with hearing protection. In this regard, new technologies are implemented in so-called augmented protectors so that the applied attenuation is automatically adapted to the background noise in contrast to the classical protectors with constant attenuation over a considerable range of input levels. This project compares speech intelligibility between those augmented and classical earplugs for normal-hearing subjects. The analyses show that certain innovations might indeed be beneficial depending on the type of background noise. Conversely, speech perception can only be ameliorated if distortion is avoided and if the positive effects of binaural listening are retained.
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author
promoter
UGent and UGent
organization
alternative title
Modelleren, meten en optimaliseren van passieve en actieve op-maat-gemaakte gehoorbeschermers
year
type
dissertation
publication status
published
subject
pages
XVI, 139 pages
publisher
Ghent University. Faculty of Medicine and Health Sciences
place of publication
Ghent, Belgium
defense location
Gent : UZ (auditorium C)
defense date
2010-01-18 17:30
language
English
UGent publication?
yes
classification
D1
additional info
dissertation consists of copyrighted materials
copyright statement
I have transferred the copyright for this publication to the publisher
id
1010005
handle
http://hdl.handle.net/1854/LU-1010005
alternative location
http://lib.ugent.be/fulltxt/RUG01/001/407/152/RUG01-001407152_2010_0001_AC.pdf
date created
2010-07-14 08:42:00
date last changed
2017-01-16 10:37:56
@phdthesis{1010005,
  abstract     = {In industry, hearing protectors are often implemented to prevent noise-induced hearing loss, but the use of protectors at the workfloor might substantially vary  from laboratory conditions. Therefore it seems advisable to also verify the attenuation in situ, for instance with the MIRE (microphone in real ear) approach.
The first aim of this research project is to investigate the implementation of the MIRE technique for custom-made hearing protectors designed with a test bore. In this channel, a MIRE measurement microphone can be slided to measure the sound pressure in the ear canal. This setup allows quick and stable measurements, but the issue is the difference in sound levels between the microphone and the eardrum.
This relationship, henceforth called transfer function, is studied in different ways. First, the transfer functions are registered with a head-and-torso-simulator (HATS) and simulated with numerical FDTD (finite-difference time-domain) models. They appear to be stable, reproducible and depend on clearly distinguishable characteristics of earplug and ear canal. 
In the second stage, transfer functions are assessed for human subjects in a similar way. They vary substantially with respect to the exact configuration in function of the frequency, but this can be predicted with individualized FDTD simulations. Based on these findings, a filter approach is developed to allow implementation in practice.  
The second aim is addressing verbal communication with hearing protection. In this regard, new technologies are implemented in so-called augmented protectors so that the applied attenuation is automatically adapted to the background noise in contrast to the classical protectors with constant attenuation over a considerable range of input levels. This project compares speech intelligibility between those augmented and classical earplugs for normal-hearing subjects. The analyses show that certain innovations might indeed be beneficial depending on the type of background noise. Conversely, speech perception can only be ameliorated if distortion is avoided and if the positive effects of binaural listening are retained.},
  author       = {Bockstael, Annelies},
  language     = {eng},
  pages        = {XVI, 139},
  publisher    = {Ghent University. Faculty of Medicine and Health Sciences},
  school       = {Ghent University},
  title        = {Modelling, measurement and optimization of passive and active custom-made hearing protectors},
  url          = {http://lib.ugent.be/fulltxt/RUG01/001/407/152/RUG01-001407152\_2010\_0001\_AC.pdf},
  year         = {2010},
}

Chicago
Bockstael, Annelies. 2010. “Modelling, Measurement and Optimization of Passive and Active Custom-made Hearing Protectors”. Ghent, Belgium: Ghent University. Faculty of Medicine and Health Sciences.
APA
Bockstael, A. (2010). Modelling, measurement and optimization of passive and active custom-made hearing protectors. Ghent University. Faculty of Medicine and Health Sciences, Ghent, Belgium.
Vancouver
1.
Bockstael A. Modelling, measurement and optimization of passive and active custom-made hearing protectors. [Ghent, Belgium]: Ghent University. Faculty of Medicine and Health Sciences; 2010.
MLA
Bockstael, Annelies. “Modelling, Measurement and Optimization of Passive and Active Custom-made Hearing Protectors.” 2010 : n. pag. Print.