Expert validation of prediction models for a clinical decision-support system in audiology.

For supporting clinical decision-making in audiology, Common Audiological Functional Parameters (CAFPAs) were suggested as an interpretable intermediate representation of audiological information taken from various diagnostic sources within a clinical decision-support system (CDSS). Ten different CAFPAs were proposed to represent specific functional aspects of the human auditory system, namely hearing threshold, supra-threshold deficits, binaural hearing, neural processing, cognitive abilities, and a socio-economic component. CAFPAs were established as a viable basis for deriving audiological findings and treatment recommendations, and it has been demonstrated that model-predicted CAFPAs, with machine learning models trained on expert-labeled patient cases, are sufficiently accurate to be included in a CDSS, but it requires further validation by experts. The present study aimed to validate model-predicted CAFPAs based on previously unlabeled cases from the same data set. Here, we ask to which extent domain experts agree with the model-predicted CAFPAs and whether potential disagreement can be understood in terms of patient characteristics. To these aims, an expert survey was designed and applied to two highly-experienced audiology specialists. They were asked to evaluate model-predicted CAFPAs and estimate audiological findings of the given audiological information about the patients that they were presented with simultaneously. The results revealed strong relative agreement between the two experts and importantly between experts and the prediction for all CAFPAs, except for the neural processing and binaural hearing-related ones. It turned out, however, that experts tend to score CAFPAs in a larger value range, but, on average, across patients with smaller scores as compared with the machine learning models. For the hearing threshold-associated CAFPA in frequencies smaller than 0.75 kHz and the cognitive CAFPA, not only the relative agreement but also the absolute agreement between machine and experts was very high. For those CAFPAs with an average difference between the model- and expert-estimated values, patient characteristics were predictive of the disagreement. The findings are discussed in terms of how they can help toward further improvement of model-predicted CAFPAs to be incorporated in a CDSS for audiology.

Voice function and voice-related quality of life in the elderly.

BACKGROUND: Many studies have referred to the effects of age on voice and the consequences of these changes. However, only little is known about the adverse effects of voice changes on quality of life in the elderly. OBJECTIVE: This study focuses on self-perception of voice in seniors as assessed by the Voice-Related Quality of Life (V-RQOL) questionnaire, on voice quality as measured by the Dysphonia Severity Index (DSI) and on the correlation between these parameters. METHODS: V-RQOL and DSI were measured as previously described in 107 non-treatment-seeking test persons without voice complaints (76 women and 31 men; mean age 78.7 ± 6.8 years, range 66-94 years). RESULTS: The mean V-RQOL value was 94.4 ± 9.8%. The mean value of the DSI in all participants was 1.2 ± 2.4. There was no significant correlation between the V-RQOL and DSI, either in women (p = 0.11), men (p = 0.58) or the whole study group (p = 0.26). CONCLUSION: Both the V-RQOL questionnaire and the DSI may be applied to seniors. As self-perception of voice and voice function do not correlate, both parameters have to be measured for voice assessment.

Computation of physiological human vocal fold parameters by mathematical optimization of a biomechanical model.

With the use of an endoscopic, high-speed camera, vocal fold dynamics may be observed clinically during phonation. However, observation and subjective judgment alone may be insufficient for clinical diagnosis and documentation of improved vocal function, especially when the laryngeal disease lacks any clear morphological presentation. In this study, biomechanical parameters of the vocal folds are computed by adjusting the corresponding parameters of a three-dimensional model until the dynamics of both systems are similar. First, a mathematical optimization method is presented. Next, model parameters (such as pressure, tension and masses) are adjusted to reproduce vocal fold dynamics, and the deduced parameters are physiologically interpreted. Various combinations of global and local optimization techniques are attempted. Evaluation of the optimization procedure is performed using 50 synthetically generated data sets. The results show sufficient reliability, including 0.07 normalized error, 96% correlation, and 91% accuracy. The technique is also demonstrated on data from human hemilarynx experiments, in which a low normalized error (0.16) and high correlation (84%) values were achieved. In the future, this technique may be applied to clinical high-speed images, yielding objective measures with which to document improved vocal function of patients with voice disorders.

Clinical value of acoustic voice measures: a retrospective study.

Within this study a retrospective analysis of clinical voice perturbation measures, Dysphonia Severity Index and subjective perceived hoarseness was performed to determine their value under clinical aspects. The study included the data of 580 healthy and 1,700 pathologic voices, which were investigated under the following aspects. The relevant parameters were identified and their interrelation determined. Group differences between healthy and pathologic voices were figured out and investigated if voice quality measures allowed an automatic diagnosis of voice disorders. The analysis revealed significant changes between the clinical groups, which indicate the diagnostic relevance of voice quality measures. However, an individual diagnosis of the underlying voice disorder failed due to a vast spread of the parameter values within the respective groups. Classification accuracies of 75-90% were achieved. The high misclassification rate of up to 25% implied that in voice disorder diagnosis, the individual interpretation of the parameter values has to be done carefully.

Objective detection and quantification of mucosal wave propagation.

In this work a detection algorithm for mucosal wave propagation is presented. By incorporating physiological knowledge of mucosal wave properties and taking the segmented lateral movement of both vocal fold edges as a basis, the spatio-temporal position of the traveling mucosal wave is identified and quantitatively captured. The course of mucosal wave propagation can be successfully detected and analyzed with regard to discriminating different types of mucosal wave activity (in terms of spread velocity and symmetry). The preliminary results obtained for six exemplary laryngeal high-speed recordings are promising and demonstrate the potential of the proposed detection and objective description approach.

Biomechanical modeling of the three-dimensional aspects of human vocal fold dynamics.

Human voice originates from the three-dimensional (3D) oscillations of the vocal folds. In previous studies, biomechanical properties of vocal fold tissues have been predicted by optimizing the parameters of simple two-mass-models to fit its dynamics to the high-speed imaging data from the clinic. However, only lateral and longitudinal displacements of the vocal folds were considered. To extend previous studies, a 3D mass-spring, cover-model is developed, which predicts the 3D vibrations of the entire medial surface of the vocal fold. The model consists of five mass planes arranged in vertical direction. Each plane contains five longitudinal, mass-spring, coupled oscillators. Feasibility of the model is assessed using a large body of dynamical data previously obtained from excised human larynx experiments, in vivo canine larynx experiments, physical models, and numerical models. Typical model output was found to be similar to existing findings. The resulting model enables visualization of the 3D dynamics of the human vocal folds during phonation for both symmetric and asymmetric vibrations.

The influence of temporal stimulus changes on speech-evoked potentials revealed by approximations of tone-evoked waveforms.

OBJECTIVE: The aim of the study was to determine whether cortical auditory potentials evoked by monosyllabic words beginning with a single consonant can be attributed to a combination of two N1/P2 complexes, temporally separated by voice-onset time (VOT). DESIGN: Cortical auditory-evoked potentials were recorded in seven normal-hearing young adults in response to two types of stimuli (a) simple tone bursts and (b) five monosyllabic words with different VOTs. Cortical burst responses (mainly consisting of N1 and P2) formed the basic functions for the simulation of speech-evoked potentials. Actually, two basic functions were created with respect to different VOTs of the speech sounds. An optimization procedure was used to determine the relative contributions of the two N1/P2 complexes. RESULTS: Speech-evoked potentials differed clearly across the stimuli. In all subjects, close matches of the synthetic and the measured waveforms could be gained for all speech sounds. The relative magnitudes of the constituent complexes differed among stimuli. CONCLUSIONS: The auditory-evoked response to a monosyllabic speech sound with short VOT can be represented by two overlapping N1/P2 complexes-one to syllable onset and the second to vowel onset. The temporal separation between the two components is well predicted by VOT, but the relative amplitudes vary across syllables. Observed variability in the fitting accuracy across subjects is small.

Automatic evaluation of tracheoesophageal substitute voice: sustained vowel versus standard text.

OBJECTIVE: The Hoarseness Diagram, a program for voice quality analysis used in German-speaking countries, was compared with an automatic speech recognition system with a module for prosodic analysis. The latter computed prosodic features on the basis of a text recording. We examined whether voice analysis of sustained vowels and text analysis correlate in tracheoesophageal speakers. PATIENTS AND METHODS: Test speakers were 24 male laryngectomees with tracheoesophageal substitute speech, age 60.6 +/- 8.9 years. Each person read the German version of the text 'The North Wind and the Sun'. Additionally, five sustained vowels were recorded from each patient. The fundamental frequency (F(0)) detected by both programs was compared for all vowels. The correlation between the measures obtained by the Hoarseness Diagram and the features from the prosody module was computed. RESULTS: Both programs have problems in determining the F(0) of highly pathologic voices. Parameters like jitter, shimmer, F(0), and irregularity as computed by the Hoarseness Diagram from vowels show correlations of about -0.8 with prosodic features obtained from the text recordings. CONCLUSION: Voice properties can reliably be evaluated both on the basis of vowel and text recordings. Text analysis, however, also offers possibilities for the automatic evaluation of running speech since it realistically represents everyday speech.

Application of automatic speech recognition to quantitative assessment of tracheoesophageal speech with different signal quality.

OBJECTIVE: Tracheoesophageal voice is state-of-the-art in voice rehabilitation after laryngectomy. Intelligibility on a telephone is an important evaluation criterion as it is a crucial part of social life. An objective measure of intelligibility when talking on a telephone is desirable in the field of postlaryngectomy speech therapy and its evaluation. PATIENTS AND METHODS: Based upon successful earlier studies with broadband speech, an automatic speech recognition (ASR) system was applied to 41 recordings of postlaryngectomy patients. Recordings were available in different signal qualities; quality was the crucial criterion for this study. RESULTS: Compared to the intelligibility rating of 5 human experts, the ASR system had a correlation coefficient of r = -0.87 and Krippendorff's alpha of 0.65 when broadband speech was processed. The rater group alone achieved alpha = 0.66. With the test recordings in telephone quality, the system reached r = -0.79 and alpha = 0.67. CONCLUSION: For medical purposes, a comprehensive diagnostic approach to (substitute) voice has to cover both subjective and objective tests. An automatic recognition system such as the one proposed in this study can be used for objective intelligibility rating with results comparable to those of human experts. This holds for broadband speech as well as for automatic evaluation via telephone.

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.

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. METHOD: A visualization procedure is presented that extracts vocal fold vibrations from HS videos and transfers the motion information into a set of three phonovibrogram (PVG) images that make visual vocal fold displacements (PVG-0), velocities (PVG-1), and accelerations (PVG-2). RESULTS: The principles of PVG computation as well as their application to three clinical examples (normal voice, laryngeal nerve paralysis, functional voice disorder with vocal nodules) are presented. For normal and dysphonic subjects, the PVG images show the characteristics of vocal fold vibrations as concern the dynamic patterns of displacements, velocities, and accelerations. CONCLUSION: The PVG approach makes visual the entire range of motion of vibrating vocal fold edges in easy-to-read color images for differentiation of normal and pathologic voices. PVG images are printable and can be stored on a hard-disc drive, enabling the documentation of the course of voice disorders that is essential for evidenced-based medicine. PVG visualization has the potential to overcome the subjective quality of assessing HS videos, which makes it a valuable tool with broad clinical application.

Spatio-temporal quantification of vocal fold vibrations using high-speed videoendoscopy and a biomechanical model.

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.

Spatiotemporal classification of vocal fold dynamics by a multimass model comprising time-dependent parameters.

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.

[Evaluation of tactile-kinesthetic perception in preschoolers: comparison of methods]. / Diagnostik der taktil-kinasthetischen Wahrnehmung bei Vorschulkindern: ein Methodenvergleich.

Tactile-kinesthetic perception (TKP) is the processing, arrangement, evaluation, and integration of sensations, which are transmitted via both surface and depth sensibility. In the phoniatric field TKP is of special importance for speech development. In this study, two German diagnostic test procedures for the assessment of TKP, i.e. the 'Diagnostischer Elternfragebogen zur taktil-kinasthetischen Responsivitat' (DEF-TK) and the 'Gottinger Entwicklungstest der taktil-kinasthetischen Wahrnehmung' (TAKIWA), were evaluated in 30 preschool children. The DEF-TK could not be analyzed in 14/30 of the children because of too many unobservable (not missing) items. This result does not correspond with data presented in the test manual but with results obtained in a former study of the reporting group. Three quarters of the children showed abnormal tactile-kinesthetic features in their DEF-TK, whereas in the TAKIWA test, a quarter of the children were found to have abnormal TKP. The DEF-TK questionnaire is not suited for clinical purposes. The nosologic and prognostic value of the TAKIWA has to be investigated in the future.

[Voice-related quality of life: structure, validity and factors of the German questionnaire]. / Stimmbezogene Lebensqualitat: Struktur, Gultigkeit und Bedingungsfaktoren des deutschen Fragebogens.

In this study, structure and validity of the German version of the Voice-Related Quality of Life (V-RQOL) questionnaire and its correlation to age, gender, and type of dysphonia (organic vs. functional) were assessed. Correlations of the V-RQOL result on the one hand and emotional and physical complaints on the other hand were investigated. Data were collected in 62 adult patients with dysphonia of benign origin and the following results were found: the German version of the V-RQOL questionnaire describes voice-related quality of life in one single value. Age, gender and type of dysphonia do not influence its result. Dysphonic patients present with an increased number of emotional and physical complaints when compared with normative values derived from the literature. However, not all of these complaints correlate with voice-related quality of life at a significant level.

Smoking, carcinophobia and Voice Handicap Index.

OBJECTIVE: This study focuses on the relation of smoking, carcinophobia and voice handicap in dysphonic patients. PATIENTS AND METHODS: Fifty-four German-speaking outpatient voice clinic attendees suffering from dysphonia of benign origin took part in this study. All patients completed the German version of the Voice Handicap Index (VHI) and were asked about their fear of suffering from laryngeal cancer without prior information about their diagnosis. RESULTS: Smokers did not fear to suffer from laryngeal cancer more than nonsmokers. However, former smokers were slightly more often found to be carcinophobic than nonsmokers. There was neither a significant difference in VHI scores comparing smokers to non- and former smokers nor when comparing carcinophobic to noncarcinophobic patients. CONCLUSION: Smoking may cause laryngeal cancer and influence the voice but does not affect patients' handicap due to dysphonia as measured by the VHI. Smoking habits do not influence the development of carcinophobia and carcinophobic dysphonic patients do not experience their voice problem differently than dysphonic patients without cancerophobia as measured by the VHI.

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.

Automatic evaluation of prosodic features of tracheoesophageal substitute voice.

In comparison with laryngeal voice, substitute voice after laryngectomy is characterized by restricted aero-acoustic properties. Until now, an objective means of prosodic differences between substitute and normal voices does not exist. In a pilot study, we applied an automatic prosody analysis module to 18 speech samples of laryngectomees (age: 64.2 +/- 8.3 years) and 18 recordings of normal speakers of the same age (65.4 +/- 7.6 years). Ninety-five different features per word based upon the speech energy, fundamental frequency F(0) and duration measures on words, pauses and voiced/voiceless sections were measured. These reflect aspects of loudness, pitch and articulation rate. Subjective evaluation of the 18 patients' voices was performed by a panel of five experts on the criteria "noise", "speech effort", "roughness", "intelligibility", "match of breath and sense units" and "overall quality". These ratings were compared to the automatically computed features. Several of them could be identified being twice as high for the laryngectomees compared to the normal speakers, and vice versa. Comparing the evaluation data of the human experts and the automatic rating, correlation coefficients of up to 0.84 were measured. The automatic analysis serves as a good means to objectify and quantify the global speech outcome of laryngectomees. Even better results are expected when both the computation of the features and the comparison method to the human ratings will have been revised and adapted to the special properties of the substitute voices.

Subjective burden in mothers of speech-impaired children.

OBJECTIVE: Evaluation of perceived subjective burden in mothers of speech-impaired children against the presence or absence of an emotional disorder. METHODS: 89 mothers (age 33.3 +/- 5.5 years, range: 19.6-43.8 years) of 89 preschool children (23 girls, 66 boys, age: 3.9 +/- 1.5 years, range: 1.6- 7.1 years) with specific speech impairment were investigated. German versions of the Hospital Anxiety and Depression Scale (HADS) and the Burden Scale for Family Caregivers (BSFC) were applied. RESULTS: 11% of the mothers met criteria for a depressive disorder (normal controls: 2.5%; p = 0.008). Twenty-eight percent of the mothers met criteria for anxiety disorders (normal controls: 9.6%; p = 0.000). The HADS depression subscore and the BSFC correlate with r = 0.75. The HADS anxiety subscore and the BSFC correlate with r = 0.59. CONCLUSIONS: Results suggest the need for routine clinical assessment of mothers' well-being when their children are affected by speech impairment.

Cortical auditory evoked potentials to acoustic changes in speech stimuli in children.

OBJECTIVE: To compare the maturation of speech-evoked N170 components of cortical auditory evoked potentials with that of tone-evoked N1 components. PATIENTS AND METHODS: Cortical auditory evoked potentials to speech and tone stimuli were derived in 42 children from age 4 to 14 years. The N170 was derived from the difference curve of responses to monosyllabic words with initial consonant-to-vowel transitions and their intensity-equivalent noise signals. RESULTS: The incidence of N1 increased from 71% below age 9 to 91% above, that of N170 tended to increase from 40 to 67% above. From age 9, adult-like morphologies of the difference waveforms were found and the time constants of N1 and N170 latency maturation were nearly identical. CONCLUSION: The N170 component is interpreted as a response to speech-specific acoustic changes such as the consonant-vowel transition. The late appearance of N170 indicates an electrophysiological correlate of speech perception that continues to develop into adolescence. Its clinical application, however, is limited due to the low incidence of N170.