Wolfgang Wokurek

Robust Estimation of Voice Quality Parameters Under Realworld Disturbances

This paper investigates the influence of different types of disturbances to the estimation of voice quality parameters. Here, voice quality is not only based on the pitch or pitch contour as in many approaches. The parameters are estimated by spectral gradients of the vocal tract compensated speech signal. We present a set of five parameters for describing the voice quality. They are used to distinguish between gender, voice qualities, and many emotional states of the speaker. We estimate them from speech signals which are corrupted by background noise and room reverberation. The paper demonstrates a certain degree of robustness of the voice quality parameters against these real world disturbances

Where and how does grammatically geared processing take place: and why is Broca's area often involved. A coordinated fMRI/ERBP study of language processing

We address the possibility of combining the results from hemodynamic and electrophysiological methods for the study of cognitive processing of language. The hemodynamic method we use is Event-Related fMRI, and the electrophysiological method measures Event-Related Band Power (ERBP) of the EEG signal. The experimental technique allows us to approach the relation between cortical structure and cognitive function in a sophisticated way. In particular, we can formulate original working hypotheses about the language-induced changes in the ongoing brain dynamics. We show, on the basis of electrophysiological data collected in an experiment on language production, that synchronized cortical networks code cognitive processes induced by language in form of power modulations of specific frequency bands. The hemodynamic (fMRI) data collected in the same task point to the existence of a central processor for the phrase structure assignment. We conceptualize such a central processor as a frequency scanner, a cortical device designed to pick up synchronized brain activity over a specific range of frequencies. We discuss the experimental designs which result from this set of hypotheses and show their relevance for the models of language processing.

Time-frequency analysis of the glottal opening

Simultaneous recordings of the laryngograph signal and speech recorded in an non-reverberating environment are investigated for acoustic evidence of the glottal opening within the microphone signal. It is demonstrated that the high resolution time-frequency analysis of the microphone signal by the smoothed pseudo Wigner distribution (SPWD) shows responses of the vocal tract to both, the glottal closure and the glottal opening. Thus, a convolution-based model for the relation between the laryngograph signal and the microphone signal is evaluated. It turns out, that the microphone signal may be viewed as a filtered version of a power function of the laryngograph signal. Hence, such a nonlinear processed laryngograph signal may be an appropriate model for the acoustic excitation of the vocal tract.

Evaluation of Phonatory Behavior and Voice Quality in Patients with Multiple Sclerosis Treated with Deep Brain Stimulation

OBJECTIVES The effect of deep brain stimulation (DBS) on phonatory behavior and voice quality in eight patients with multiple sclerosis (MS) was examined instrumentally and perceptually. The acoustic signals of vowel productions obtained from patients (produced with and without stimulation) and from a group of 16 healthy control speakers were analyzed to prove statistically the changes of phonatory behavior and voice quality. STUDY DESIGN This is a randomized study. METHODS Firstly, a new parametrization was used to determine phonatory behavior. Secondly, a perceptual evaluation of voice quality of the same speech material was performed. RESULTS With stimulation, phonation has a greater tendency to be strained. The results of perceptual evaluation support this strained phonation behavior under stimulation, resulting in a smaller degree of breathiness ratings of all raters. Without stimulation, an impaired and partly disturbed adduction of the vocal folds can be shown. These findings are also supported in the perceptual experiment providing a higher degree of hoarseness ratings of all raters for these signals. CONCLUSIONS High-frequency electrical impulses to the thalamus in patients with MS influence the phonatory behavior of their vocal folds. The results suggest the need for long-term monitoring of phonatory behavior during DBS to initiate adequate treatments without delay.