Impact of Subharmonic and Aperiodic Laryngeal Dynamics on the Phonatory Process Analyzed in Ex Vivo Rabbit Models

Normal voice is characterized by periodic oscillations of the vocal folds. On the other hand, disordered voice dynamics (e.g., subharmonic and aperiodic oscillations) are often associated with voice pathologies and dysphonia. Unfortunately, not all investigations may be conducted on human subjects; hence animal laryngeal studies have been performed for many years to better understand human phonation. The rabbit larynx has been shown to be a potential model of the human larynx. Despite this fact, only a few studies regarding the phonatory parameters of rabbit larynges have been performed. Further, to the best of our knowledge, no ex vivo study has systematically investigated phonatory parameters from high-speed, audio and subglottal pressure data with irregular oscillations. To remedy this, the present study analyzes experiments with sustained phonation in 11 ex vivo rabbit larynges for 51 conditions of disordered vocal fold dynamics. (1) The results of this study support previous findings on non-disordered data, that the stronger the glottal closure insufficiency is during phonation, the worse the phonatory characteristics are; (2) aperiodic oscillations showed worse phonatory results than subharmonic oscillations; (3) in the presence of both types of irregular vibrations, the voice quality (i.e., cepstral peak prominence) of the audio and subglottal signal greatly deteriorated compared to normal/periodic vibrations. In summary, our results suggest that the presence of both types of irregular vibration have a major impact on voice quality and should be considered along with glottal closure measures in medical diagnosis and treatment.

Juvenile Ovine Ex Vivo Larynges: Phonatory, Histologic, and Micro CT Based Anatomic Analyses

It is well known that the phonatory process changes during the life span. However, detailed investigations on potential factors concerned are rare. To deal with this issue, we performed extended biomechanical, macro anatomical, and histological analyses of the contributing laryngeal structures in ex vivo juvenile sheep models. Altogether twelve juvenile sheep larynges were analyzed within the phonatory experiments. Three different elongation levels and 16 different flow levels were applied to achieve a large variety of phonatory conditions. Vocal fold dynamics and acoustical and subglottal signals could be analyzed for 431 experimental runs. Subsequently, for six juvenile larynges microcomputed tomography following virtual 3D reconstruction was performed. The remaining six juvenile larynges as well as six ex vivo larynges from old sheep were histologically and immunohistologically analyzed. Results for juveniles showed more consistent dynamical behavior compared to old sheep larynges due to vocal fold tissue alterations during the life span. The phonatory process in juvenile sheep seems to be more effective going along with a greater dynamic range. These findings are supported by the histologically detected higher amounts of elastin and hyaluronic acid in the lamina propria of the juvenile sheep. The 3D reconstructions of the thyro-arytenoid muscles (TAM) showed a symmetrical shape. Intraindividual volume and surface differences of the TAM were small and comparable to those of aged sheep. However, TAM dimensions were statistically significant smaller for juvenile larynges. Finally, topographical landmarks were introduced for later comparison with other individuals and species. This work resulted in detailed functional, immunohistological, and anatomical information that was not yet reported. This data will also provide reference information for therapeutic strategies regarding aging effects, e.g. laryngeal muscle treatment by functional electrical stimulation.

The effect of emotion on voice production and speech acoustics

The study of emotional expression in the voice has typically relied on acted portrayals of emotions, with the majority of studies focussing on the perception of emotion in such portrayals. The acoustic characteristics of natural, often involuntary encoding of emotion in the voice, and the mechanisms responsible for such vocal modulation, have received little attention from researchers. The small number of studies on natural or induced emotional speech have failed to identify acoustic patterns specific to different emotions. Instead, most acoustic changes measured have been explainable as resulting from the level of physiological arousal characteristic of different emotions. Thus measurements of the acoustic properties of angry, happy and fearful speech have been similar, corresponding to their similar elevated arousal levels. An opposing view, the most elaborate description of which was given by Scherer (1986), is that emotions affect the acoustic characteristics of speech along a number of dimensions, not only arousal. The lack of empirical data supporting such a theory has been blamed on the lack of sophistication of acoustic analyses in the little research that has been done.By inducing real emotional states in the laboratory, using a variety of computer administered induction methods, this thesis aimed to test the two opposing accounts of how emotion affects the voice. The induction methods were designed to manipulate some of the principal dimensions along which, according to multidimensional theories, emotional speech is expected to vary. A set of acoustic parameters selected to capture temporal, fundamental frequency (F0), intensity and spectral vocal characteristics of the voice was extracted from speech recordings. In addition, electroglottal and physiological measurements were made in parallel with speech recordings, in an effort to determine the mechanisms underlying the measured acoustic changes.The results indicate that a single arousal dimension cannot adequately describe a range of emotional vocal changes, and lend weight to a theory of multidimensional emotional response patterning as suggested by Scherer and others. The correlations between physiological and acoustic measures, although small, indicate that variations in sympathetic autonomic arousal do correspond to changes to F0 level and vocal fold dynamics as indicated by electroglottography. Changes to spectral properties, speech fluency, and F0 dynamics, however, can not be fully explained in terms of sympathetic arousal, and are probably related as well to cognitive processes involved in speech planning.