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Normative Study of 192 Healthy Subjects
As basis of our investigations into the nonverbal information contained in human
speech, we have carried out a normative study with 192 healthy volunteers,
stratified according to age, sex and education. The specific design of this study
with 3 different types of text and 2 repeated measurements at 14 day intervals
has been particularly chosen in order to analyse the reproducibility of the major
speech parameters as well as their sensitivity to form and content of spoken text.
In addition, we wanted to derive reference values of the general population and
to learn to distinguish between normal fluctuations and significant changes over
time.
Principal Goals
Principal goals: (1) determining an optimum
recording time containing enough information for a reliable estimation of speech
parameters, (2) determining the distribution of the inter-individual scattering
of speech parameters in the general population, (3) determining the intra-individual
stability of speech parameters over time (in order to learn to distinguish between
normal fluctuations and significant changes), (4) determining possible differences
in the speech parameters between dialect and non-dialect, and between affect-neutral
and affect-charged speech, (5) determining the amount of variance explainable by the
external factors age, sex and social status, and (6) developing a practical procedure
which is free of interactions during recording and which can easily be carried out
in a standard form by a technician.
Speech Recordings
Prior to the recordings, the test persons were asked to fill out the BfS
questionnaire [von Zerssen 1987] which measures the momentary emotional state.
Immediately following this, the test persons were led to the recording studio where
they were asked to count loud from 1 to 40 and to present their personal history
free-hand in their native dialect and with their normal voice. This procedure took
about 2 minutes and was used to calibrate the recording. After voice calibration,
a well-defined tone of 5 seconds duration was recorded on tape for the calibration
of loudness. Under the assumption that this counting and free-hand speaking helped
the test persons to relax, the actual measurement was carried out according to the
following plan:
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Counting out loud from 1 to 40 (0.5 min)
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Short pause (maximum 0.5 min)
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Emotionally neutral text from a children's book (2 min)
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Short pause (maximum 0.5 min)
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Emotionally stimulating text from a well-known author (2 min)
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Counting out loud from 1 to 40 (0.5 min)
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Stability of speech parameters "mean vocal pitch" and "6db-bandwidth" as a
function of time (healthy volunteers): the first assessment is plotted along the
x-axis and the second assessment 14 days later along the y-axis.
While mean vocal pitch displays a high stability over time, the speech parameter
"6db-bandwidth" (measuring intonation) is much less stable. The experimental condition
is "counting/frehand speech" and the sample comprises 91 healthy subjects.
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