Untersuchungen der rhythmischen Struktur von Sprache unter Alkoholeinfluss

This thesis is concerned with the rhythmical structure of speech
under the influence of alcohol. All analyses presented are based on
the Alcohol Language Corpus, which is a collection of speech
uttered by 77 female and 85 male sober and intoxicated speakers.
Experimental research was carried out to find robust, automatically
extractable features of the speech signal that indicate speaker
intoxication. These features included rhythm measures, which
reflect the durational variability of vocalic and consonantal
elements and are normally used to classify languages into different
rhythm classes. The durational variability was found to be greater
in the speech of intoxicated individuals than in the speech of
sober individuals, which suggests, that speech of intoxicated
speakers is more irregular than speech of sober speakers. Another
set of features describes the dynamics of the short-time energy
function of speech. Therefore different measures are derived from a
sequence of energy minima and maxima. The results also reveal a
greater irregularity in the speech of intoxicated individuals. A
separate investigation about speaking rate included two different
measures. One is based on the phonetic segmentation and is an
estimate of the number of syllables per second. The other is the
mean duration of the time intervals between successive maxima of
the short-time energy function of speech. Both measures denote a
decreased speaking rate in the speech of intoxicated speakers
compared to speech uttered in sober condition. The results of a
perception experiment show that a decrease in speaking rate also is
an indicator for intoxication in the perception of speech. The last
experiment investigates rhythmical features based on the
fundamental frequency and energy contours of speech signals.
Contours are compared directly with different distance measures
(root mean square error, statistical correlation and the Euclidean
distance in the spectral space of the contours). They are also
compared by parameterization of the contours using Discrete Cosine
Transform and the first and second moments of the lower DCT
spectrum. A Principal Components Analysis on the contour data was
also carried out to find fundamental contour forms regarding the
speech of intoxicated and sober individuals. Concerning the
distance measures, contours of speech signals uttered by
intoxicated speakers differ significantly from contours of speech
signals uttered in sober condition. Parameterization of the
contours showed that fundamental frequency contours of speech
signals uttered by intoxicated speakers consist of faster movements
and energy contours of speech signals uttered by intoxicated
speakers of slower movements than the respective contours of speech
signals uttered in sober condition. Principal Components Analysis
did not find any interpretable fundamental contour forms that could
help distinguishing contours of speech signals of intoxicated
speakers from those of speech uttered in sober condition. All
analyses prove that the effects of alcoholic intoxication on
different features of speech cannot be generalized but are to a
great extent speaker-dependent.