the impact of head and body postures on the acoustic speech signal

254 Pages·2015·3.99 MB·English

by  Yvonne Flory

THE IMPACT OF HEAD AND BODY POSTURES ON
THE ACOUSTIC SPEECH SIGNAL

YVONNE FLORY
CHURCHILL COLLEGE

THIS DISSERTATION IS SUBMITTED FOR THE DEGREE OF DOCTOR OF
PHILOSOPHY AT THE UNIVERSITY OF CAMBRIDGE.

SEPTEMBER 2014

Preface
This dissertation describes work undertaken at the Department of Theoretical and
Applied Linguistics between October 2011 and June 2014, under the supervision
of Prof Francis Nolan.
Part I, comprising chapters 1 – 5, lays out the motivation and empiric background
for the thesis.
Part II, which contains chapters 6 – 9, describes the original research I have
carried out to address the research questions of my PhD.
Part III, consisting of chapters 10 and 11, puts the original research described in
this dissertation in context with findings in prior research.
I hereby declare that this thesis is not substantially the same as any that I have
submitted for a degree or diploma or other qualification at any other university.
I further state that no part of my thesis has already been or is being currently
submitted for any such degree, diploma or other qualification.
This thesis is the result of my own work and includes nothing which is the
outcome of work done in collaboration.

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Statement of length
This thesis does not exceed the word limit of 80,000 words set by the Faculty of
Modern and Medieval Languages, including footnotes, references and appendices,

but excluding bibliographies.
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Abstract
“The impact of head and body postures on the acoustic speech signal”
by Yvonne Flory

This dissertation is aimed at investigating the impact of postural changes within
speakers on the acoustic speech signal to complement research on articulatory
changes under the same conditions. The research is therefore relevant for forensic
phonetics, where quantifying within-speaker variation is vital for the accuracy of
speaker comparison.
To this end, two acoustic studies were carried out to quantify the influence of five
head positions and three body orientations on the acoustic speech signal. Results
show that there is a consistent change in the third formant, a change which was
most evident in the body orientation measurements, and to a lesser extent in the
head position data. Analysis of the results with respect to compensation strategies
indicates that speakers employ different strategies to compensate for these
perturbations to their vocal tract. Some speakers did not exhibit large differences
in their speech signal, while others appeared to compensate much less. Across all
speakers, the effect was much stronger in what were deemed ‘less natural’,
postures. That is, speakers were apparently less able to predict and compensate for
the impact of prone body orientation on their speech than for that of the more
natural supine orientation.
In addition to the acoustic studies, a perception experiment assessed whether
listeners could make use of acoustic cues to determine the posture of the speaker.
Stimuli were chosen with, by design, stronger or weaker acoustic cues to posture,
in order to elicit a possible difference in identification performance. Listeners
were nevertheless not able to identify above chance whether a speaker was sitting
or lying in prone body orientation even when hearing the set with stronger cues.
Further combined articulatory and acoustic research will have to be carried out to
disentangle which articulatory behaviours correlate with the acoustic changes
presented in order to draw a more comprehensive picture of the effects of postural
variation on speech.
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Acknowledgements
I am grateful to everyone who has supported me while writing my dissertation. In
particular, I am indebted to my supervisor, Professor Francis Nolan, for all his
constructive criticism and support. His guidance was exceptional and fundamental
for the completion of my PhD. I would also like to thank my advisor, Dr Kirsty
McDougall, for continuous advice and feedback.
The Arts & Humanities Research Council, as well as Churchill College and the
University of Cambridge, deserve my gratitude for regular and emergency
funding respectively, without which I would not have been able to undertake my
research.
Completing an extensive project like this would not have been possible without
the support of the other members of the Phonetics lab, past and present, who have
been supportive through good and bad moments (in alphabetical order by last
name): Ricky Chan, Dr Calbert Graham, Anna Jespersen, Gerry Kwek, Dr Aike
Li, Dr Brechtje Post, Elaine Schmidt. I am also grateful to Geoffrey Potter and Ian
Smeeton, who helped with technical matters.
I would like to thank my friends in Cambridge and Saarbrücken, most notably Dr
Christopher Berry and Carl Sequeira for proofreading, and Melanie Kucharczyk
and Jennifer Bender for having been such great friends for so many years now.
Last, but not least, I would like to express my endless gratitude to Dr Kayvan
Sadeghzadeh for support on all levels and for having been my rock throughout the
last two and a half years.
This thesis is dedicated to my mother, who is not only an excellent mother, but
also a truly good friend; and Günter, whose appreciation means very much to me.
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