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This paper is concerned with a novel methodology for generating phonetic questions used in tree-based state tying for speech recognition. In order to implement a speech recognition system, language-dependent knowledge which goes beyond annotated material is usually required. The approach presented here generates phonetic questions for decision trees are based on a feature table that summarizes the articulatory characteristics of each sound. On the one hand, this method allows better language-specific triphone models to be defined given only a feature-table as linguistic input. On the other hand, the feature-table approach facilitates efficient definition of triphone models for other languages since again only a feature table for this language is required. The approach is exemplified with speech recognition systems for English and Thai.
HMMs are the dominating technique used in speech recognition today since they perform well in overall phone recognition. In this paper, we show the comparison of HMM methods and machine learning techniques, such as neural networks, decision trees and ensemble classifiers with boosting and bagging in the task of articulatory-acoustic feature classification. The experimental results show that HMM methods work well for the classification of such features as vocalic. However, decision tree and bagging outperform HMMs for the fricative classification task since the data skewness is much higher than for the feature vocalic classification task. This demonstrates that HMMs do not perform as well as decision trees and bagging in highly skewed data settings.
MRI data of German vowels and consonants was acquired for 9 speakers. In this paper tongue contours for the vowels were analyzed using the three-mode factor analysis technique PARAFAC. After some difficulties, probably related to what constitutes an adequate speaker sample for this three-mode technique to work, a stable two-factor solution was extracted that explained about 90% of the variance. Factor 1 roughly captured the dimension low back to high front; Factor 2 that from mid front to high back. These factors are compared with earlier models based on PARAFAC. These analyses were based on midsagittal contours; the paper concludes by illustrating from coronal and axial sections how non-midline information could be incorporated into this approach.
Analyses of jaw movement(obtained by Electromagnetic Articulography) and acoustics show that loud speech is an intricate phenomenon. Besides involving higher intensity and subglottal pressure it affects jaw movements as well as fundamental frequency and especially first formants. It is argued that all these effects serve the purpose of enhancing perceptual salience.
The vowel quality in some diphthongs of Swabian (an upper german dialect) was determined by measurement of first and second formant values. A minimal contrast could be shown between two different diphthong qualities […], where for Standard German only one is assumed, viz. /ai/. The two diphthong qualities differ only slightly in onset and offset vowel quality, so a better understanding of their relationship was expected from an examination of their dynamic aspects. Our preliminary results suggest that there is indeed a difference in the temporal structure of the two diphthongs.