From children to adults: how binaural cues and ear canal impedances grow [Elektronische Ressource] / vorgelegt von Janina Fels

Janina Fels

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• Gesundheit

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• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2008
• Nombre de lectures: 13
• Langue: English
• Poids de l'ouvrage: 13 Mo

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Aachener Beiträge zur
Technischen Akustik
In this thesis the growth-dependency of head-related transfer functions
JaninaFels
and their resulting parameters (interaural time and level differences) are
analyzed as well as ear canal impedances.
FromChildrentoAdults:
Differences in the anatomy of children and adults result in different
HowBinauralCuesand
binaural cues. The individual anthropometric parameters, however, affect
EarCanalImpedancesGrow
the binaural cues to a varying extent. In this thesis the most important
anthropometric parameter with regard to their influence on binaural cues,
are determined. Ear canal impedances are undergoing certain changes as
well while children are growing up and finally reach adulthood. This thesis
presents for the first time, the age-related development of data that is most
decisive for the impedances.
Thesenewfindingsopenupnewpossibilitiestodevelopartificialchildheads
and couplers for hearing aids that are suitable for children. Thus, improve-
ments in certain fields of applications such as the development and fitting
of hearing aids for children are now possible and measurement techniques
that are used for classroom acoustics can now be optimized significantly as
well. Moreover, these new findings are vital when it comes to re-evaluating
standardized artificial heads.
λογος
ISSN 1866-3052
λογος
ISBN 978-3-8325-1855-4
LogosVerlag Berlin
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5FROMCHILDRENTOADULTS:
HOWBINAURALCUESAND
EARCANALIMPEDANCESGROW
Von der Fakula¨t fu¨r Elektrotechnik und Informationstechnik der
Rheinisch-Westfalischen Technischen Hochschule Aachen¨
zur Erlangung des akademischen Grades einer
DOKTORIN DER INGENIEURWISSENSCHAFTEN
genehmigte Dissertation
vorgelegt von
Diplom-Ingenieurin
Janina Fels
aus Monchengladbach¨
Berichter: Universitatsprofessor Dr. rer. nat. Michael Vorlander¨ ¨
Universit¨atsprofessor Dr.-Ing. Peter Vary
Tag der mu¨ndlichen Pru¨fung: 30. Januar 2008
DieseDissertationistaufdenInternetseitenderHochschulbibliothekonlineverfugbar.¨Contents
Abstract – Zusammenfassung vi
Introduction 1
1 Basics 7
1.1 The Auditory System . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 Head-Related Transfer Functions and Binaural Cues . . . . . . . . . . 8
1.2.1 Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.2.2 Interaural Time and Level Differences . . . . . . . . . . . . . . 13
1.2.3 Artificial Heads . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.3 Ear Canal Impedances . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.3.1 Importance of the Ear Canal Impedance . . . . . . . . . . . . 17
1.3.2 Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
I Outer Ear (Blocked Ear Canal) 23
2 Determination of Head-Related Transfer Functions 24
2.1 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3 Comparison of Simulation and Measurement . . . . . . . . . . . . . . 33
3 Anthropometric Parameters and CAD Modeling 37
3.1 Photogrammetry – A Method to obtain Anthropometric Data . . . . 42
3.1.1 Basics of Photogrammetry . . . . . . . . . . . . . . . . . . . . 42
3.1.2 Calibration of the Cameras . . . . . . . . . . . . . . . . . . . 44
3.1.3 Image Orientation and Stereo Measurement . . . . . . . . . . 45
3.1.4 Definition of a Head-Related Coordinate System . . . . . . . . 48
3.2 CAD Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.2.1 Individual Model vs. Parametric Model . . . . . . . . . . . . . 50
3.2.2 Determination of a Parametric Model . . . . . . . . . . . . . . 51
3.3 Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
iii4 Anthropometric Data and its Influence on Binaural Cues and
HRTFs 57
4.1 Case Study – Infant’s HRTF vs. Adult’s HRTF . . . . . . . . . . . . 57
4.2 Statistics of the Anthropometric Data of the Head and Torso . . . . . 59
4.3 Parameter Variations of the Head and Torso Geometry . . . . . . . . 64
4.3.1 Effects on HRTF . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.3.2 Influence on HRIR . . . . . . . . . . . . . . . . . . . . . . . . 69
4.3.3 Influence on ITD . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.3.4 Influence on ILD . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.3.5 Additional Parameter Variations of Head and Torso Geometry
on basis of Young Adults . . . . . . . . . . . . . . . . . . . . . 73
4.4 Parameter Variations of the Pinna Geometry . . . . . . . . . . . . . . 75
4.4.1 Effects on HRTF and HRIR . . . . . . . . . . . . . . . . . . . 76
4.4.2 Influence on ITD . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.4.3 Influence on ILD . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
II Ear Canal 85
5 Determination of Ear Canal Impedances 86
5.1 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.2 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.3 Comparison of Simulation and Measurement . . . . . . . . . . . . . . 98
6 Anthropometric Data and its Influence on Ear Canal Impedances 101
6.1 Ear Canal Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.2 Ear Canal Impedances of Children and Adults . . . . . . . . . . . . . 104
6.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
III Applications and Summary 113
7 Applications 114
7.1 Pilot Study: Hearing Impairment . . . . . . . . . . . . . . . . . . . . 116
7.2 Pilot Studies: Room Acoustics . . . . . . . . . . . . . . . . . . . . . . 116
8 Summary and Outlook 123
9 Kurzfassung 129
9.1 Grundlagen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
9.2 Ermittlung von Aussenohrubertragungsfunktionen . . . . . . . . . . . 131¨
iv9.3 Datenerhebung der anthropometrischen Parameter und CAD-
Modellierung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.4 Analyse der anthropometrischen Daten . . . . . . . . . . . . . . . . . 133
9.5 Ermittlung von Geho¨rgangsimpedanzen . . . . . . . . . . . . . . . . . 135
9.6 Analyse der Gehorgangsparameter . . . . . . . . . . . . . . . . . . . . 137¨
9.7 Anwendungen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
9.8 Zusammenfassung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Glossary 142
Curriculum Vitae 143
Danksagung 144
Bibliography 146
vAbstract – Zusammenfassung
Abstract
In this thesis the growth-dependency of head-related transfer functions and their
resulting parameters (interaural time and level differences) are analyzed as well as
ear canal impedances.
Custom-designed measurements for children were developed which made it pos-
sible to obtain anthropometric data from different kinds of subjects, ranging from
infants to adults. The obtained data is statistically evaluated with regard to its influ-
ence on binaural cues and ear canal impedances with the help of suitable simulation-
and measurement techniques.
It becomes evident that children and adults differ tremendously as far as their
respective head-related transfer functions are concerned. Furthermore it turns out
that the head-related transfer function of a child cannot be obtained by scaling down
the dimensions of an adult head. Differences in the anatomy of children and adults
thus result in different binaural cues. The individual anthropometric parameters,
however, affect the binaural cues to a varying extent. In this thesis the most im-
portant anthropometric parameter with regard to their influence on binaural cues,
are determined. Ear canal impedances are undergoing certain changes as well while
children are growing up and finally reach adulthood. This thesis presents for the first
time, the age-related development of data that is most decisive for the impedances.
These new findings open up new possibilities to develop artificial child heads and
couplersforhearingaidsthataresuitableforchildren. Thus,improvementsincertain
fields of applications such as the development and fitting of hearing aids for children
are now possible and measurement techniques that are used for classroom acoustics
can now be optimized significantly as well. Moreover, these new findings are vital
when it comes to re-evaluating standardized artificial heads.
viZusammenfassung
In dieser Arbeit werden die Wachstumsabhangigkeiten von Außenohrubertragungs-¨ ¨
funktionen und daraus abgeleiteten Großen (Interaurale Zeit- und Pegelunterschiede)¨
sowie von Geho¨rgangsimpedanzen untersucht.
Fu¨r die Untersuchung an Kindern entwickelte Verfahren machen es mo¨glich, die
anthropometrischen Par