Search

Background: A standardized questionnaire on central auditory processing disorders ["Anamnesebogen zur Erfassung auditiver Verarbeitungs- und Wahrnehmungsstörungen (AVWS)"] was developed by the German Society of Phoniatrics and Pediatric Audiology and standardized for school-age children. This study was designed to elucidate the validity of this questionnaire in preschool children., Methods: The responses, which were given by the parents of 84 preschool children with respect to auditory discrimination and auditory memory, were correlated with the results of the Heidelberg screening test for preschool children (HVS), and their accuracy of prediction was determined., Results: Similar to the results of other studies in school-age children, weak but significant correlations were found between the questionnaire results regarding auditory discrimination and auditory memory and the respective results of the HVS subtests. With a few exceptions, the questionnaire's accuracy of prediction was low., Conclusion: For preschool children, the questionnaire provides a reasonable method to get specific information about a child's history in a standardized and economic way. However, it is not valid as a screening or diagnostic tool.

High-speed laryngeal endoscopic systems record vocal fold vibrations during phonation in real-time. For a quantitative analysis of vocal fold dynamics a metrical scale is required to get absolute laryngeal dimensions of the recorded image sequence. For the clinical use there is no automated and stable calibration procedure up to now. A calibration method is presented that consists of a laser projection device and the corresponding image processing for the automated detection of the laser calibration marks. The laser projection device is clipped to the endoscope and projects two parallel laser lines with a known distance to each other as calibration information onto the vocal folds. Image processing methods automatically identify the pixels belonging to the projected laser lines in the image data. The line detection bases on a Radon transform approach and is a two-stage process, which successively uses temporal and spatial characteristics of the projected laser lines in the high-speed image sequence. The robustness and the applicability are demonstrated with clinical endoscopic image sequences. The combination of the laser projection device and the image processing enables the calibration of laryngeal endoscopic images within the vocal fold plane and thus provides quantitative metrical data of vocal fold dynamics.

Pathologic changes within the organic constitution of vocal folds or a functional impairment of the larynx may result in disturbed or even irregular vocal fold vibrations. The consequences are perturbations of the acoustic speech signal which are perceived as a hoarse voice. By means of appropriate image processing techniques, the vocal fold dynamics are extracted from digital high-speed videos. This study addresses the approach to obtain a parametric description of the spatio-temporal characteristics of the vocal fold oscillations for the aim of classification. For this purpose a biomechanical vocal fold model is introduced. An automatic optimization procedure is developed for fitting the model dynamics to the observed vocal fold oscillations. Thus, the resulting parameter values represent a specific vibration pattern and serve as an objective quantification measure. Performance and reliability of the optimization procedure are validated with synthetically generated data sets. The high-speed videos of two normal voice subjects and six patients suffering from different voice disorders are processed. The resulting model parameters represent a rough approximation of physiological parameters along the entire vocal folds.

Introduction: Malfunctions of the human voice with unknown causes are denoted by "functional voice disorders". The high speed video imaging technique (HVT) allows the recording of the oscillating vocal folds in real time. A new method is presented, describing different types of oscillation and their onset mathematically. A precise classification of the kind of functional voice disorders is possible., Methods: For 71 young women, from the HVT recordings two parameters were mathematically estimated, reflecting the phonation onset dynamics: The threshold value A(th), corresponding with the myoelastic tone of the vocal folds and a maximum sound pressure level of speech L(max), characterising the efficiency of voice., Results: Both values are sensitive for functional voice disorders and enable a differentiation between these pathologies., Discussion: Significant differences of the computed parameters between the pathological groups and normal voices substantiate the presented method as a stable and objective tool for medical diagnosis.

A model-based approach is proposed to objectively measure and classify vocal fold vibrations by left-right asymmetries along the anterior-posterior direction, especially in the case of nonstationary phonation. For this purpose, vocal fold dynamics are recorded in real time with a digital high-speed camera during phonation of sustained vowels as well as pitch raises. The dynamics of a multimass model with time-dependent parameters are matched to vocal fold vibrations extracted at dorsal, medial, and ventral positions by an automatic optimization procedure. The block-based optimization accounts for nonstationary vibrations and compares the vocal fold and model dynamics by wavelet coefficients. The optimization is verified with synthetically generated data sets and is applied to 40 clinical high-speed recordings comprising normal and pathological voice subjects. The resulting model parameters allow an intuitive visual assessment of vocal fold instabilities within an asymmetry diagram and are applicable to an objective quantification of asymmetries.

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.

Event-related potentials (ERPs) as part of the EEG are applied to assess auditory processing in children. Mismatch negativity (MMN) is a change-specific component of ERPs that indicates a pre-cognitive discrimination process. MMN responses were recorded in 10 healthy preschool children to four different types of signal changes. The signals investigated were processed using a discrete wavelet transform (DWT) to analyze the characteristics of the ERP components. All children showed distinct MMN that was significant in all tasks. The MMN amplitudes varied between subjects and depended on the different tasks. The wavelet transform allowed simplified analysis and quantification of the MMN component, as well as the double-peak structure of the P1 component. The variation in MMN amplitudes suggests the possibility of determining individual auditory profiles. Owing to the shorter time required, the MMN paradigm suggested combined with the DWT proposed offers a new objective investigation method for children.

Objective: This study investigated the influence of epilarynx area on an excised human vocal fold during phonation., Study Design: A hemilarynx set-up using an excised human larynx was used. An artificial vocal tract with an epilarynx tube of variable cross-sectional area was attached. High-speed imaging was performed and standard phonatory variables were measured., Results: Glottal airflow, fundamental frequency, and sound level increased as a function of subglottal pressure. A decrease in epilarynx area decreased phonation threshold pressure, glottal airflow, and vocal fold displacements and velocities., Conclusions: Preliminary experimental results confirm that narrowing the epilarynx area facilitates phonation by decreasing phonation threshold pressure, presumably through impedance matching of the glottal source and vocal tract., Significance: As this phenomenon associated with epilarynx narrowing is further quantified and generalized, eventually new surgical alterations of the epilaryngeal structure may be suggested to facilitate phonation, in addition to standard phonosurgical procedures.

Classification of vocal fold vibrations is an essential task of the objective assessment of voice disorders. For historical reasons, the conventional clinical examination of vocal fold vibrations is done during stationary, sustained phonation. However, the conclusions drawn from a stationary phonation are restricted to the observed steady-state vocal fold vibrations and cannot be generalized to voice mechanisms during running speech. This study addresses the approach of classifying real-time recordings of vocal fold oscillations during a nonstationary phonation paradigm in the form of a pitch raise. The classification is based on asymmetry measures derived from a time-dependent biomechanical two-mass model of the vocal folds which is adapted to observed vocal fold motion curves with an optimization procedure. After verification of the algorithm performance the method was applied to clinical problems. Recordings of ten subjects with normal voice and ten dysphonic subjects have been evaluated during stationary as well as nonstationary phonation. In the case of nonstationary phonation the model-based classification into "normal" and "dysphonic" succeeds in all cases, while it fails in the case of sustained phonation. The nonstationary vocal fold vibrations contain additional information about vocal fold irregularities, which are needed for an objective interpretation and classification of voice disorders.

To increase our understanding of pathological and healthy voice production, quantitative measurement of the medial surface dynamics of the vocal folds is significant, albeit rarely performed because of the inaccessibility of the vocal folds. Using an excised hemilarynx methodology, a new calibration technique, herein referred to as the linear approximate (LA) method, was introduced to compute the three-dimensional coordinates of fleshpoints along the entire medial surface of the vocal fold. The results were compared with results from the direct linear transform. An associated error estimation was presented, demonstrating the improved accuracy of the new method. A test on real data was reported including computation of quantitative measurements of vocal fold dynamics.

Quantitative measurement of the medial surface dynamics of the vocal folds is important for understanding how sound is generated within the larynx. Building upon previous excised hemilarynx studies, the present study extended the hemilarynx methodology to the in vivo canine larynx. Through use of an in vivo model, the medial surface dynamics of the vocal fold were examined as a function of active thyroarytenoid muscle contraction. Data were collected using high-speed digital imaging at a sampling frequency of 2000 Hz, and a spatial resolution of 1024 x 1024 pixels. Chest-like and fry-like vibrations were observed, but could not be distinguished based on the input stimulation current to the recurrent laryngeal nerve. The subglottal pressure did distinguish the registers, as did an estimate of the thyroarytenoid muscle activity. Upon quantification of the three-dimensional motion, the method of Empirical Eigenfunctions was used to extract the underlying modes of vibration, and to investigate mechanisms of sustained oscillation. Results were compared with previous findings from excised larynx experiments and theoretical models.

After a total excision of the larynx, mucosal tissue at the upper part of the esophagus can be used as a substitute voice generating element. The properties of the tissue dynamics are closely related to the substitute voice quality. The process of substitute voice is investigated by recording simultaneously the acoustic signal with a microphone and the vibrations of the voice generator with a digital high-speed camera. We propose an automatic image-processing technique which is applied to analyze the vibration pattern of the substitute voice generating element. First, an initialization step detects the voice generator within a high-speed sequence. Second, a combination of a threshold technique and an active contour algorithm tracks the tissue deformations of the substitute voice generator. The applicability of the algorithm is shown in three high-speed recordings. For the first time, tissue deformations of substitute voice generating elements are successfully tracked. The results of the image processing procedure are used to describe quantitatively the temporal properties of the substitute voice generator. Comparisons of the spectral components of tissue deformations and tracheoesophageal voice signals reveal the close relationship between the vibration pattern of the substitute voice generator and the quality of substitute voice.

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.

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.

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., Study Design: An experimental study in which 9 adults underwent high-speed endoscopy combined with a laser projection device., Methods: The projection system consists of two parallel laser beams with a distance of 3.8 mm. It is mounted on the tip of a rigid endoscope, which is attached to a digital high-speed camera During development and design, examination situations were taken into account. Two laser spots are projected onto the vocal folds and enable the definition of a metric scale within the endoscopic image. Knowledge-based image processing algorithms were used for evaluation., Results: First measurements of the vocal fold length during phonation were performed in a group of nine healthy male students. The determination of glottal length during phonation agrees with former results. Quantifying vocal fold velocities in absolute units makes it possible to estimate the initial collision forces., Conclusions: The presented laser projection system allows the determination of absolute measures in the larynx. Because of the simple functional principle, the system is open for use without digital high-speed recording as well. Absolute units may also be helpful in voice diagnosis and in monitoring during voice therapy.