VOWELS IN STANDARD AUSTRIAN GERMAN - Acoustics ...

Sylvia Moosmüller
The speech material thus obtained was digitised at 22.050 Hz, 16 Bit with the
workstation STx (http://www.kfs.oeaw.ac.at).
2.2. Measurements
In total, approximately 11.000 vowels were analysed. The vowels were segmented
manually. In the case of preceding voiceless segments, the first positive zero crossing or
the end of aperiodicity was determined as the start of the vowel. The last full period
similar to the preceding ones, or the start of aperiodicity was determined as the end of
the vowel. Figure 2.1 gives an example for segmentation of a vowel in a fricative –
plosive context. The cursors in the spectrogram window are positioned at the start and
the end of the vowel. The waveform zoom window (left upper panel) at position 0 32
ensures the exact positioning at the first positive zero crossing, referring to the left
cursor position. The segmentation served as a duration measurement as well.
Formant frequency candidates were extracted by means of a Linear Prediction
Coding (LPC) algorithm such as published by Markel & Gray (1976). At a sampling
frequency of 22.050 Hz, a 46 ms long gliding Hanning window was applied with an
overlap of 95%, using 26 coefficients and providing sufficient measurement points for
fast formant transitions and short signal segments. Fundamental frequency
measurements were performed by means of an autocorrelation method (SIFT:
Simplified Inverse Filter Tracking), synchonized with the formant frequency analysis.
32 Not to be confused with the cursors (crosses) in the waveform zoom window, which are
positioned to measure the duration of the period, with the values displayed in the left
column at the bottom.
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