Verifying the attenuation of earplugs in situ : Method validation on human subjects including individualized numerical simulations

The microphone in real ear (MIRE) protocol allows the assessment of hearing protector's (HPD) attenuation in situ by measuring the difference between the sound pressure outside and inside the ear canal behind the HPD. Custom-made earplugs have been designed with an inner bore to insert the MIRE...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2009-03, Vol.125 (3), p.1479-1489
Main Authors: Bockstael, Annelies, Van Renterghem, Timothy, Botteldooren, Dick, D'Haenens, Wendy, Keppler, Hannah, Maes, Leen, Philips, Birgit, Swinnen, Freya, Vinck, Bart
Format: Article
Language:English
Subjects:
Acoustics
Adolescent
Adult
Auditory Perception
Ear Canal
Exact sciences and technology
Female
Fundamental areas of phenomenology (including applications)
Hearing Aids
Humans
Male
Middle Aged
Noise: its effects and control
Physics
Reproducibility of Results
Young Adult
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Summary:The microphone in real ear (MIRE) protocol allows the assessment of hearing protector's (HPD) attenuation in situ by measuring the difference between the sound pressure outside and inside the ear canal behind the HPD. Custom-made earplugs have been designed with an inner bore to insert the MIRE probe containing two microphones, the reference microphone measuring the sound pressure outside and the measurement microphone registering the sound pressure behind the HPD. Previous research on a head and torso simulator reveals a distinct difference, henceforth called transfer function, between the sound pressure at the MIRE measurement microphone and the sound pressure of interest at the eardrum. In the current study, similar measurements are carried out on humans with an extra microphone to measure the sound pressure at the eardrum. The resulting transfer functions confirm the global frequency dependency found earlier, but also show substantial variability between the ears with respect to the exact frequency and amplitude of the transfer functions' extrema. In addition, finite-difference time-domain numerical models of an ear canal with earplug are developed for each individual ear by including its specific geometrical parameters. This approach leads to a good resemblance between the simulations and their corresponding measurements.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.3075603