Jörg Lohscheller

Phonovibrography: Mapping High-Speed Movies of Vocal Fold Vibrations Into 2-D Diagrams for Visualizing and Analyzing the Underlying Laryngeal Dynamics

Endoscopic high-speed laryngoscopy in combination with image analysis strategies is the most promising approach to investigate the interrelation between vocal fold vibrations and voice disorders. So far, due to the lack of an objective and standardized analysis procedure a unique characterization of vocal fold vibrations has not been achieved yet. We present a visualization and analysis strategy which transforms the segmented edges of vibrating vocal folds into a single 2-D image, denoted Phonovibrogram (PVG). Within a PVG the individual type of vocal fold vibration becomes uniquely characterized by specific geometric patterns. The PVG geometries give an intuitive access on the type and degree of the laryngeal asymmetry and can be quantified using an image segmentation approach. The PVG analysis was applied to 14 representative recordings derived from a high-speed database comprising normal and pathological voices. We demonstrate that PVGs are capable to differentiate and quantify different types of normal and pathological vocal fold vibrations. The objective and precise quantification of the PVG geometry may have the potential to realize a novel classification of vocal fold vibrations.

Clinically evaluated procedure for the reconstruction of vocal fold vibrations from endoscopic digital high-speed videos

Investigation of voice disorders requires the examination of vocal fold vibrations. State of the art is the recording of endoscopic high-speed movies which capture vocal fold vibrations in real-time. It enables investigating the interrelation between disturbances of vocal fold vibrations and voice disorders. However, the lack of clinical studies and of a standardized procedure to reconstruct vocal fold vibrations from high-speed videos constrain the clinical acceptance of the high-speed technique. An image processing approach is presented that extracts the vibrating vocal fold edges from digital high-speed movies. The initial segmentation is principally based on a seeded region-growing algorithm. Even in movies with low image quality the algorithm segments successfully the glottal area by an introduced two-dimensional threshold matrix. Following segmentation, the vocal fold edges are reconstructed from the computed time-varying glottal area. The performance of the procedure was objectively evaluated within a study comprising 372 high-speed recordings. The accuracy of vocal fold reconstruction exceeds manual segmentation results obtained by clinical experts. The algorithm reaches an information flow-rate of up to 98 images per second. The robustness and high accuracy of the procedure makes it suitable for the application in clinical routine. It enables an objective and highly accurate description of vocal fold vibrations which is essential to realize extensive clinical studies which focus on the classification of voice disorders.

Vibration parameter extraction from endoscopic image series of the vocal folds

An approach is given to extract parameters affecting phonation based upon digital high-speed recordings of vocal fold vibrations and a biomechanical model. The main parameters which affect oscillation are vibrating masses, vocal fold tension, and subglottal air pressure. By combining digital high-speed observations with the two-mass-model by Ishizaka and Flanagan (1972) as modified by Steinecke and Herzel (1995), an inversion procedure has been developed which allows the identification and quantization of laryngeal asymmetries. The problem is regarded as an optimization procedure with a nonconvex objective function. For this kind of problem, the choice of appropriate initial values is important. This optimization procedure is based on spectral features of vocal fold movements. The applicability of the inversion procedure is first demonstrated in simulated vocal fold curves. Then, inversion results are presented for a healthy voice and a hoarse voice as a case of functional dysphonia caused by laryngeal asymmetry.

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.

Classification of unilateral vocal fold paralysis by endoscopic digital high-speed recordings and inversion of a biomechanical model

Hoarseness in unilateral vocal fold paralysis is mainly due to irregular vocal fold vibrations caused by asymmetries within the larynx physiology. By means of a digital high-speed camera vocal fold oscillations can be observed in real-time. It is possible to extract the irregular vocal fold oscillations from the high-speed recordings using appropriate image processing techniques. An inversion procedure is developed which adjusts the parameters of a biomechanical model of the vocal folds to reproduce the irregular vocal fold oscillations. Within the inversion procedure a first parameter approximation is achieved through a knowledge-based algorithm. The final parameter optimization is performed using a genetic algorithm. The performance of the inversion procedure is evaluated using 430 synthetically generated data sets. The evaluation results comprise an error estimation of the inversion procedure and show the reliability of the algorithm. The inversion procedure is applied to 15 healthy voice subjects and 15 subjects suffering from unilateral vocal fold paralysis. The optimized parameter sets allow a classification of pathologic and healthy vocal fold oscillations. The classification may serve as a basis for therapy selection and quantification of therapy outcome in case of unilateral vocal fold paralysis.

How Low Can You Go? Physical Production Mechanism of Elephant Infrasonic Vocalizations

The Song of the Elephant In mammals, vocal sound production generally occurs in one of two ways, either through muscular control—as when a cat purrs or, more commonly, by air passing through the vocal folds—which occurs in humans and facilitates production of extremely high frequency bat calls. Over the past 20 years, it has been recognized that elephants can communicate through extremely low frequency infrasonic sounds. Taking advantage of a natural death of an elephant in a zoo, Herbst et al. (p. 595) examined the biomechanics of elephant sound production in an excised elephant larynx. Self-sustained vocal-fold vibrations, without the presence of any neural control, were used to produce infrasonic elephant sounds, using the same mechanism as singing in humans and echolocation in bats. Elephants produce low-frequency sounds via intrinsic vocal-fold vibrations similar to those in humans. Elephants can communicate using sounds below the range of human hearing (“infrasounds” below 20 hertz). It is commonly speculated that these vocalizations are produced in the larynx, either by neurally controlled muscle twitching (as in cat purring) or by flow-induced self-sustained vibrations of the vocal folds (as in human speech and song). We used direct high-speed video observations of an excised elephant larynx to demonstrate flow-induced self-sustained vocal fold vibration in the absence of any neural signals, thus excluding the need for any “purring” mechanism. The observed physical principles of voice production apply to a wide variety of mammals, extending across a remarkably large range of fundamental frequencies and body sizes, spanning more than five orders of magnitude.

Quality of Life in Laryngectomees after Prosthetic Voice Restoration

Background: In oncology, the paradigms for evaluating the results of treatment have shifted over the last few years. Preserving or restoring the quality of life has become an equally important aim of medical treatment as complete excision of the tumor and the duration of patient survival. Following laryngectomy, adequate speech restoration is one major aim of therapy. Different replacement strategies of voice production such as tracheoesophageal speech, esophageal speech, or electrolarynx are in use. The reporting department is able to restore speech in more than 90% of the patients; the majority uses tracheoesophageal speech with Provox® voice prosthesis. The purpose of the study was to assess the quality of life in laryngectomees after successful voice restoration with Provox voice prosthesis. Patients and Methods: In a cross-sectional study 25 laryngectomees whose voice had been restored by tracheoesophageal puncture and Provox voice prosthesis were examined for quality of life. The Short Form 36-Item Health Survey (SF-36) was used as an international and highly standardized test. Results: In comparison with a standardized healthy German male population, the patients showed more limited physical functioning as well as more restricted physical and emotional role functions. However, the laryngectomees did not attain lower scores for bodily pain. According to the patients’ statements their social functioning, vitality, and their mental health were not excessively limited; mental health and vitality were even better than in patients with heart or renal failure and hepatitis C. General health was fairly similar to a standard population. Conclusions: After laryngectomy, patients have deficits in physical and emotional well-being. Concepts of therapy should increasingly focus on how to deal with physical limitations and the patient’s apperception. Successfully restored voice minimizes social, mental and vitality limitations. The SF-36 is a suitable instrument for quality of life assessment in order to define disease-dependent and individual limitations of quality of life in laryngectomees and should lead to individual interventions.

Phonovibrogram Visualization of Entire Vocal Fold Dynamics

Objectives: High‐speed (HS) video recordings are the up‐to‐date method for visualizing irregular vocal fold vibrations. However, perceptive evaluation during offline replay is time consuming and shows high inter‐rater variability.

Voice Handicap of Laryngectomees with Tracheoesophageal Speech

The evaluation of diagnostics and therapies includes more and more subjective, i.e. emotional and social aspects. Focussing on the handicap experienced by dysphonic patients, the Voice Handicap Index (VHI) has previously been found to be of significant clinical and scientific value for different voices. In this study the VHI questionnaire was applied to demonstrate the voice handicap of 20 male laryngectomees using tracheoesophageal voice (Provox®), aged 65.5 ± 8.7 years. Their VHI was 45.5 ± 24.1, which was significantly higher than the score of patients with functional voice disorders, but differed only slightly from patients with organic laryngeal dysphonia. Focussing on individual data, VHI scores ranged from values similar to persons without voice disorder to maximum handicap of 101. Comparing the VHI scores with the laryngectomees’ gradual self-perception of voice disorder severity, no consistent relationship was found. Considering the large interindividual differences, the VHI may serve as a valuable instrument for the assessment of individual interventional needs rather than for the identification of a general laryngectomees’ handicap.

Intelligibility of laryngectomees’ substitute speech: automatic speech recognition and subjective rating

Substitute speech after laryngectomy is characterized by restricted aero-acoustic properties in comparison with laryngeal speech and has therefore lower intelligibility. Until now, an objective means to determine and quantify the intelligibility has not existed, although the intelligibility can serve as a global outcome parameter of voice restoration after laryngectomy. An automatic speech recognition system was applied on recordings of a standard text read by 18 German male laryngectomees with tracheoesophageal substitute speech. The system was trained with normal laryngeal speakers and not adapted to severely disturbed voices. Substitute speech was compared to laryngeal speech of a control group. Subjective evaluation of intelligibility was performed by a panel of five experts and compared to automatic speech evaluation. Substitute speech showed lower syllables/s and lower word accuracy than laryngeal speech. Automatic speech recognition for substitute speech yielded word accuracy between 10.0 and 50% (28.7±12.1%) with sufficient discrimination. It complied with experts’ subjective evaluations of intelligibility. The multi-rater kappa of the experts alone did not differ from the multi-rater kappa of experts and the recognizer. Automatic speech recognition serves as a good means to objectify and quantify global speech outcome of laryngectomees. For clinical use, the speech recognition system will be adapted to disturbed voices and can also be applied in other languages.