Michael Döllinger

High‐Precision Measurement of the Vocal Fold Length and Vibratory Amplitudes

Objective/Hypothesis Standard laryngoscopy suffers from a lack of information about the actual size of the observed objects (i.e., vocal fold length and oscillating amplitudes). However, there is much interest in absolute measures for both clinical and research purposes. Therefore, a laser projection device has been developed that enables the precise determination of absolute units in endoscopic investigation during respiration and phonation.

Glissando: laryngeal motorics and acoustics

The objective of this study was to investigate the laryngeal mechanisms and the acoustical signal during a glissando. In particular, glottal length, maximum glottal area, and vibratory amplitudes during a glissando maneuver of a healthy male adult were measured. An endoscopic high-speed system combined with a laser projection device was used to obtain quantitative data both in the time and spatial domains. Simultaneously to the endoscopic investigation, the acoustic signal was recorded. Fundamental frequency and sound pressure level derived from the acoustic recordings were compared to vocal fold length and glottis area derived from the high-speed recordings. Results were used for interpretation of the phonation mechanism during glissando by means of laryngeal and acoustic parameters. The transition between the chest register and the falsetto register was identified by the absence of vocal fold contact. A rather early onset of the falsetto register was observed at 160 Hz. Although fundamental frequency of the vocal folds increased linearly even at the transition point, sound pressure level dropped down. These data represent the first ever quantitative description and interpretation of the glissando based on both voice properties and laryngeal motorics. In the presented example of an untrained singer, the falsetto sets in at comparatively low frequencies. Although the chest-falsetto transition is rather smooth for laryngeal motorics and voice pitch, a sudden drop of voice intensity was observed.

Quantitative analysis of organic vocal fold pathologies in females by high-speed endoscopy.

Quantitative analysis of endoscopic high‐speed video recordings of vocal fold vibrations has been growing in importance in recent years. The videos have mainly been analyzed using subjective evaluation, but this is examiner dependent, and the results show inadequate interobserver agreement. The aims of this study were therefore to identify appropriate objective parameters for analyzing high‐speed recordings to differentiate healthy voice production from organic disorders.

Spatiotemporal Analysis of High-Speed Videolaryngoscopic Imaging of Organic Pathologies in Males

PURPOSEnThe aim of this study was to identify parameters that would differentiate healthy from pathological organic-based vocal fold vibrations to emphasize clinical usefulness of high-speed imaging.nnnMETHODnFifty-five men (M age = 36 years, SD = 20 years) were examined and separated into 4 groups: 1 healthy (26 individuals) and 3 pathological (10 individuals with contact granuloma, 12 with polyps, and 7 with cysts). Vocal fold vibrations were recorded using a high-speed camera during sustained phonation. Twenty objective glottal area waveform and 24 phonovibrogram parameters representing spatiotemporal characteristics were analyzed. Statistical group comparisons were performed to document spatiotemporal changes for organic lesions that cannot be determined visually. To look for specific pattern profiles within organic lesions, the authors performed linear discriminant analysis.nnnRESULTSnThirteen parameters showed significant differences between the healthy group and at least 1 pathological group. The differences occurred more in temporal than in spatial parameters. Contact granuloma showed the fewest statistical differences (3 parameters), followed by cysts (9 parameters), and polyps (10 parameters). Linear discriminant analysis achieved accuracy performance of 76% (all groups separated) and 82% (healthy vs. pathological).nnnCONCLUSIONnThe results suggest that for males, the differences between healthy voices and organic voice disorders may be more pronounced within temporal characteristics that cannot be visually detected without high-speed imaging.

Assessment of local vocal fold deformation characteristics in an in vitro static tensile test.

Voice quality is strongly dependent on vocal fold dynamics, which in turn are dependent on lung pressure and vocal fold biomechanics. Numerical and physical models are often used to investigate the interactions of these different subsystems. However, the utility of numerical and physical models is limited unless appropriately validated with data from physiological models. Hence a method that enables analysis of local vocal fold deformations along the entire surface is presented. In static tensile tests, forces are applied to distinctive working points being located in cover and muscle, respectively, so that specific layer properties can be investigated. The forces are directed vertically upward and are applied along or above the vocal fold edge. The resulting deformations are analyzed using multiple perspectives and three-dimensional reconstruction. Deformation characteristics of four human vocal folds were investigated. Preliminary results showed two phases of deformation: a range with a small slope for small deformations fading into a significant nonlinear deformation trend with a high slope. An increase of tissue stiffness from posterior to anterior was detected. This trend is more significant for muscle and in the mid-anterior half of the vocal fold.

Evaluation of Analytical Modeling Functions for the Phonation Onset Process

The human voice originates from oscillations of the vocal folds in the larynx. The duration of the voice onset (VO), called the voice onset time (VOT), is currently under investigation as a clinical indicator for correct laryngeal functionality. Different analytical approaches for computing the VOT based on endoscopic imaging were compared to determine the most reliable method to quantify automatically the transient vocal fold oscillations during VO. Transnasal endoscopic imaging in combination with a high-speed camera (8000u2009fps) was applied to visualize the phonation onset process. Two different definitions of VO interval were investigated. Six analytical functions were tested that approximate the envelope of the filtered or unfiltered glottal area waveform (GAW) during phonation onset. A total of 126 recordings from nine healthy males and 210 recordings from 15 healthy females were evaluated. Three criteria were analyzed to determine the most appropriate computation approach: (1) reliability of the fit function for a correct approximation of VO; (2) consistency represented by the standard deviation of VOT; and (3) accuracy of the approximation of VO. The results suggest the computation of VOT by a fourth-order polynomial approximation in the interval between 32.2 and 67.8% of the saturation amplitude of the filtered GAW.

Robust Automatic Evaluation of Intelligibility in Voice Rehabilitation Using Prosodic Analysis

Speech intelligibility for voice rehabilitation has been successfully evaluated by automatic prosodic analysis. In this paper, the influence of reading errors and the selection of certain words for the computation of prosodic features (nouns only, nouns and verbs, beginning of each sentence, beginnings of sentences and subclauses) are examined. 73 hoarse patients (48.3 ± 16.8 years) read the German version of the text “The North Wind and the Sun”. Their intelligibility was evaluated perceptually by 5 trained experts according to a 5-point scale. Eight prosodic features showed human-machine correlations of r (ge ) 0.4. The normalized energy in a word-pause-word interval, computed from all words (r = 0.69 for the full speaker set), the mean of jitter in nouns and verbs (r = 0.67), and the pause duration before a word (r = 0.66) were the most robust features. However, reading errors can significantly influence these results.

Visualization of Intelligibility Measured by Language-Independent Features

Automatic intelligibility assessment using automatic speech recognition is usually language-specific. In this study, a language-independent approach based on alignment-free phonological and phonemic features is proposed. It utilizes models that are trained with Flemish speech, and it is applied to assess dysphonic German speakers. In order to visualize the results, two techniques were tested: a plain selection of most relevant features emerging from Ensemble Linear Regression involving feature selection, and a Sammon transform of all the features to a 3-D space. The test data comprised recordings of 73 hoarse persons (48.3 ± 16.8 years) who read the German version of the text “The North Wind and the Sun”. The reference evaluation was obtained by five speech therapists and physicians who rated intelligibility according to a 5-point Likert scale. In the 3-D visualization, the different levels of intelligibility were clearly separated. This could be the basis for an objective support for diagnostics in voice and speech rehabilitation.

Visualisierung und Interpretation von Stimmlippenschwingungen

Fur die quantitative Bewertung der pathologischen Stimme ist die Messung und Analyse der Stimmlippenbewegungen von zentraler Bedeutung. Rauhigkeit, ein typisches Symptom des kranken Kehlkopfes, beruht auf irregularen, im Extremfall auf chaotischen Stimmlippenschwingungen. Die Messung der Stimmlippenschwingungen gelingt in Echtzeit mit einer fur medizinische Zwecke angepassten Hochgeschwindigkeitskamera. Die Schwingungen konnen mit sogenannten Kymogrammen visualisiert werden. Diese Kymogramme liefern den zeitabhangigen Bewegungsverlauf der Stimmlippen entlang einer Linie von anterior nach posterior. In diesem Beitrag wird beschrieben, inwieweit durch eine Erweiterung auf Mehrlinienkymogramme auch ortsabhangige Schwingungsmoden (anterior-posterior Moden) dargestellt und quantifiziert werden konnen.

Analyse von digitalen Hochgeschwindigkeitsvideos der Ersatzstimmgebung

Bei Verlust des Kehlkopfes im Rahmen einer Tumorbehandlung (Laryngektomie) kann eine Rehabilitation der Stimme ermoglicht werden, indem die Speiserohre durch ein Einweg-Ventil aus Silikon (Stimmventilprothese) mit der Luftrohre verbunden wird. Mithilfe der Stimmventilprothese konnen beim Ausatmen Schleimhaute in der Speiserohre durch den Luftstrom in Schwingungen versetzt und so als Quelle einer Ersatzstimme genutzt werden. Die Qualitat der Ersatzstimme ist wesentlich durch die Schwingungscharakteristik der Schleimhaute bestimmt. Zur Visualisierung des Stimmgebungsprozesses wurden simultan digitale Hochgeschwindigkeitsvideos der Schleimhautbewegungen und das akustische Signal wahrend der Phonation aufgezeichnet. Zur Bestimmung der fur den Stimmgebungsprozess relevanten Bildanteile wurde eine Korrelationsanalyse von Bildsequenzen und den dazugehorigen akustischem Signalen vorgenommen.