Acoustic Analysis of Voluntary Coughs, Throat Clearings, and Induced Reflexive Coughs in a Healthy Population.

Cough efficacy is considered a reliable predictor of the aspiration risk in head and neck cancer patients with radiation-associated dysphagia. Currently, coughing is assessed perceptually or aerodynamically. The goal of our research is to develop methods of acoustic cough analysis. In this study, we examined in a healthy population the acoustical differences between three protective maneuvers: voluntary cough, voluntary throat clearing, and induced reflexive cough. Forty healthy participants were included in this study. Voluntary cough, voluntary throat clearing, and reflexive cough samples were recorded and analyzed acoustically. Temporal acoustic features were the following: the slope and curvature of the amplitude contour, as well as the average, slope, and curvature of the sample entropy and kurtosis contours of the recorded signal. Spectral features were the relative energy in the frequency bands (0-400 Hz, 400-800 Hz, 800-1600 Hz, 1600 Hz-3200 Hz, > 3200 Hz) as well as the weighted spectral energy. Results showed that, compared to a voluntary cough, a throat clearing starts with a weaker onset pulse and involves oscillations from the onset to the offset (concave curvature of the amplitude contour, p < 0.05), lower average (p < 0.05), and slope (p < 0.05) as well as lower convex curvature (p < 0.05) of the kurtosis contour. An induced reflexive cough starts with a higher and briefer onset burst and includes higher frication noise (larger convexity of the curvature of the amplitude and kurtosis contours (p < 0.05)) compared to a voluntary cough. The conclusion is that voluntary coughs are acoustically significantly different from voluntary throat clearings and induced reflexive coughs.

Diplophonia Disturbs Jitter and Shimmer Measurement.

OBJECTIVES: The aims of this study are to investigate the effects of diplophonia on jitter and shimmer and to identify measurement limitations with regard to material selection and clinical interpretation. MATERIALS AND METHODS: Four hundred and ninety-eight audio samples of sustained phonations were analyzed. The audio samples were assessed for the grade of hoarseness and the presence of diplophonia. Jitter and shimmer were reported with regard to perceptual ratings. We investigated cycle marker positions exemplarily and qualitatively to understand their implications for perturbation measurements. RESULTS: Medians of jitter and shimmer were higher for diplophonic voices than for nondiplophonic voices with equal grades of hoarseness. The variance of jitter for moderately dysphonic voices was larger than the variance observed in a corpus from which diplophonic samples had been discarded. The positions of cycle markers in diplophonic voices did not match the positions of the pulses, indicating that the validity of jitter and shimmer values for these voices were questionable. CONCLUSION: Diplophonia biases the reporting of dysphonia severity via perturbation measures, and their validity is questionable for these voices. In addition, diplophonia is an influential source of variance in jitter measurements. Thus, diplophonic fragments of voice samples should be excluded prior to perturbation analysis.

Smoothness of an equation for the glottal flow rate versus the glottal area.

This letter proposes a correction to an equation by Titze [J. Acoust. Soc. Am. 75, 570-580 (1984)] for the volume velocity of the glottal air flow given the glottal area and other laryngeal parameters. It shows that the equation produces non-differentiable waveforms at the instants of glottal closure and opening, if the glottal area is also not differentiable at those instants. By adding an air viscosity term to the equation, twice-differentiability is obtained. Also, the letter corrects a sign error in the original formulation.

Self-entrainment of the right and left vocal fold oscillators.

This article presents an analysis of entrained oscillations of the right and left vocal folds in the presence of asymmetries. A simple one-mass model is proposed for each vocal fold. A stiffness asymmetry and open glottis oscillations are considered first, and regions of oscillation are determined by a stability analysis and an averaging technique. The results show that the subglottal threshold pressure for 1:1 entrainment increases with the asymmetry. Within that region, both folds oscillate with the same amplitude and with the lax fold delayed in time with regard to the tense fold. At large asymmetries, a region involving several different phase entrainments or toroidal regimes at constant threshold pressure appears. The effect of vocal fold collisions and asymmetry in the damping coefficients of the oscillators are explored next by means of numerical analyses. It is shown that the damping asymmetry expands the 1:1 entrainment region at low subglottal pressures across the whole asymmetry range. In the expanded region, the oscillator with the lowest natural frequency is dominant and the other oscillator has a large phase advance and small amplitude. The theoretical results are finally compared with data collected from a mechanical replica of the vocal folds.

Assessment of radio(chemo)therapy-related dysphagia in head and neck cancer patients based on cough-related acoustic features: a prospective phase II national clinical trial (ACCOUGH-P/A trial).

BACKGROUND: Radiation-associated dysphagia is defined as impaired swallowing efficiency/safety following (chemo)radiotherapy in head and neck cancer patients. In a dysphagia framework, impaired coughing may lead to lung aspiration and fatal lung infection. Although cough efficacy is a predictor of the risk of aspiration, cough investigation is minimal in patients with radiation-associated dysphagia. Because cough is a transient signal, existing software for speech analysis are not appropriate. The goal of our project is to develop an assessment method using acoustic features related to voluntary and reflexive coughs as biomarkers of the risk of penetration/aspiration in patients with radiation-associated dysphagia. METHODS: Healthy subjects and head and neck cancer patients with and without dysphagia will produce voluntary coughs, throat clearings and reflexive coughs. Recordings will be made using an acoustic microphone and a throat microphone. The recorded signals will be manually segmented and subsequently analysed with a software under development. Automatic final segmentation enables to measure cough duration. The first method of analysis includes temporal features: the amplitude contour, the sample entropy and the kurtosis. These features report respectively the strength, the unpredictability (turbulence noise due to the air jet) and the impulsive quality (burst) of the signal. The second method of analysis consists of a spectral decomposition of the relative cough signal energy into several frequency bands (0-400 Hz, 400-800 Hz, 800-1600 Hz, 1600-3200 Hz, > 3200 Hz). The primary outcome of this exploratory research project is the identification of a set of descriptive acoustic cough features in healthy subjects as reference data (ACCOUGH). The secondary outcome of this research in head and neck cancer patients with radiation-associated dysphagia includes the identification of (1) a set of descriptive acoustic cough features as biomarkers of penetration-aspiration (ACCOUGH-P/A), (2) swallowing scores, (3) voice features and (4) aerodynamic cough features. DISCUSSION: This study is expected to develop methods of acoustic cough analysis to enhance the assessment of radiation-associated dysphagia in head and neck cancer patients following (chemo)radiation. TRIAL REGISTRATION: International Standard Randomized Controlled Trials Number (ISRCTN) registry ISRCTN16540497. Accepted on 23 June 2023.

Development and perceptual assessment of a synthesizer of disordered voices.

A synthesizer is based on a nonlinear wave-shaping model of the glottal area, an algebraic model of the glottal aerodynamics as well as concatenated-tube models of the trachea and vocal tract. Voice disorders are simulated by way of models of vocal frequency jitter and tremor, vocal amplitude shimmer and tremor, as well as pulsatile additive noise. Six experiments have been carried out to assess the synthesizer perceptually. Three experiments involve the perceptual categorization of male synthetic and human stimuli and one the auditory discrimination between synthetic and human tokens. A fifth experiment reports the auditory discrimination between synthetic tokens with different levels of additive and modulation noise. A sixth experiment reports the scoring by expert listeners of male synthetic stimuli on equal-appearing interval scales grade-roughness-breathiness (GRB). A first objective is to demonstrate the ability of the synthesizer to simulate vowel sounds that are valid exemplars of speech sounds produced by humans with voice disorders. A second objective is to learn how human expert raters perceptually map vocal frequency, additive and modulation noise as well as vowel categories into scores on GRB scales.

Assessment of cough in head and neck cancer patients at risk for dysphagia-An overview.

BACKGROUND: This literature review explores the terminology, the neurophysiology, and the assessment of cough in general, in the framework of dysphagia and regarding head and neck cancer patients at risk for dysphagia. In the dysphagic population, cough is currently assessed perceptually during a clinical swallowing evaluation or aerodynamically. RECENT FINDINGS: Recent findings have shown intra and inter-rater disagreements regarding perceptual scoring of cough. Also, aerodynamic measurements are impractical in a routine bedside assessment. Coughing, however, is considered to be a clinically relevant sign of aspiration and dysphagia in head and cancer patients treated with concurrent chemoradiotherapy. CONCLUSION: This article surveys the literature regarding the established cough assessment and stresses the need to implement innovative methods for assessing cough in head and neck cancer patients treated with concurrent chemoradiotherapy at risk for dysphagia.

Detection of Diplophonation in Audio Recordings of German Standard Text Readings.

OBJECTIVES: Diplophonia is a common symptom of voice disorder that is in need of objectification. We investigated whether diplophonia can be detected from audio recordings of text readings by means of dedicated audio signal processing, ie, a descendant of a formerly published "Diplophonia Diagram." STUDY DESIGN: Diagnostic study. METHODS: Forty subjects were included who had been clinically rated in the past as diplophonic. For each subject, the audio signal of the German standard text "Der Nordwind und die Sonne" was recorded. First, subject groups regarding the frequency of occurrence of diplophonic episodes were established via manual labeling of audio recordings. Reference boundaries of diplophonic time intervals and the boundaries of voiced time intervals were manually obtained. Each time interval was labeled as diplophonic or nondiplophonic, as well as voiced or unvoiced. The diplophonia rate was defined as the total duration of diplophonation among the total duration of voiced phonation. Based on the diplophonia rate obtained from manual annotations, subjects were distinguished who were (1) frequently diplophonic, (2) unfrequently diplophonic, and (3) nondiplophonic during the reading of the standard text. Second, the grouping was predicted automatically via audio signal processing, and the performance of automatic prediction was evaluated. The audio recordings were analyzed with a purpose-built audio signal processor that estimated the diplophonia rate automatically. Two cut-off threshold classifiers were trained to detect automatically (1) frequently diplophonic, and (2) nondiplophonic subjects. In addition, multinomial logistic regression was performed to enable automatic 3-way classification. RESULTS: Among all subjects, 14 were frequently diplophonic during the reading of the text, 14 were unfrequently diplophonic, and the remaining 12 were nondiplophonic. In automated detection of frequently diplophonic subjects, a sensitivity of 71% and a specificity of 88% were obtained. The sensitivity and specificity regarding automated detection of nondiplophonic subjects were 68% and 92%. In 3-way classification, 62.5% of the subjects were classified into the correct group. CONCLUSIONS: Only two-thirds of the subjects who had been labeled as diplophonic on the base of auditory impression during clinical anamnesis diplophonated during the reading of a standard text. This demonstrates that the ecological validity of audio recordings of standard text readings is limited. Subject groups regarding the frequency of occurrence of diplophonic episodes were established and audio signal processing enabled automated classification. The observed performance of automated classification was promising and may be relevant to future clinical and scientific work. Possible applications include objective clinical voice assessment for diagnostic purposes and feedback based training of clinical raters.

Maximal Ambient Noise Levels and Type of Voice Material Required for Valid Use of Smartphones in Clinical Voice Research.

PURPOSE: Smartphone technology provides new opportunities for recording standardized voice samples of patients and transmitting the audio files to the voice laboratory. This drastically improves the achievement of baseline designs, used in research on efficiency of voice treatments. However, the basic requirement is the suitability of smartphones for recording and digitizing pathologic voices (mainly characterized by period perturbations and noise) without significant distortion. In a previous article, this was tested using realistic synthesized deviant voice samples (/a:/) with three precisely known levels of jitter and of noise in all combinations. High correlations were found between jitter and noise to harmonics ratio measured in (1) recordings via smartphones, (2) direct microphone recordings, and (3) sound files generated by the synthesizer. In the present work, similar experiments were performed (1) in the presence of increasing levels of ambient noise and (2) using synthetic deviant voice samples (/a:/) as well as synthetic voice material simulating a deviant short voiced utterance (/aiuaiuaiu/). RESULTS: Ambient noise levels up to 50 dBA are acceptable. However, signal processing occurs in some smartphones, and this significantly affects estimates of jitter and noise to harmonics ratio when formant changes are introduced in analogy with running speech. The conclusion is that voice material must provisionally be limited to a sustained /a/.

Testing the reliability of Grade, Roughness and Breathiness scores by means of synthetic speech stimuli.

This article describes a synthesizer of disordered voices and reports a test of the reliability of Grade, Roughness, and Breathiness scores assigned to synthetic stimuli by eight expert listeners in two sessions. Speech stimuli [a], [i], [u], [ai], and [ia] were synthesized with three values of vocal frequency and four levels of vocal jitter and pulsatile additive noise each. The agreement and correlation of scores assigned by the same rater in different sessions, or by different raters in the same session, accord with published data. Only a small part of the variance of the arithmetic differences between the scores that are assigned to the same stimulus is explained by the stimuli properties. The conclusion is that differences between scores that are assigned to the same stimulus are not attributable to biases of individual raters; such biases would shift all the scores assigned on a scale, and the shift would be interpretable in terms of the properties of the stimuli.

Voice quality in patients suffering from bipolar disease.

People suffering from bipolar disease are more and more common. Such pathology can severely affect patients' lifestyle by wide, and sometimes extreme, mood swings. Biosignals can be very useful to understand this disease. Specifically, speech-related features have been seen to vary in depressed people with respect to healthy subjects. Usually prosodic, spectral and energy-related features are studied. Some further information, instead, can be provided studying voice quality. According to Laver's model, voice quality is sensitive and depends on both anatomic/physiologic issues and long-term muscular adjustments of the larynx or the supraglottal vocal tract. A pilot study on both bipolar patients and healthy control subjects, performed by means of the Long-Term Average Spectrum (LTAS) is presented. The effects on LTAS estimation of a F0-correction procedure are discussed. Pairwise statistical comparisons between subjects in euthymic and depressed states and euthymic and hypomanic states were performed. Significant differences were found in some frequency intervals in both cases. The F0-correction procedure modified the values of the significant frequency intervals in the euthymic/depressed comparison, that also was characterized by a change of F0. Noticeably, no statistically significant differences were found in control subjects acquired in the same mood state. Though the number of subjects is small, the results are encouraging given their coherence across patients and the lack of differences in the control group. Finally, this work suggests that particular vocal settings might be involved in different mood states.

Impact of vocal load on breathiness: perceptual evaluation.

OBJECTIVES: To evaluate the impact on voice of 2 hours of continuous oral reading. METHODS: Fifty normophonic women underwent two sessions of voice loading in which the required intensity level varied: 60-65 dB(A) for the first session, and 70-75 dB(A) for the second session. Ten expert judges evaluated the breathiness of one sentence recorded before and after each loading session. Pairs of stimuli were presented randomly to the judges, who were asked to designate the breathiest sample. RESULTS: A significant decrease in breathiness was observed following both sessions, suggesting an improvement of voice subsequent to loading. When comparing the two intensity levels, no difference was found for breathiness after vocal loading.

Validity of jitter measures in non-quasi-periodic voices. Part II: the effect of noise.

In this paper the effect of noise on both perceptual and automatic evaluation of the glottal cycle length in irregular voice signals (sustained vowels) is studied. The reliability of four tools for voice analysis (MDVP, Praat, AMPEX, and BioVoice) is compared to visual inspection made by trained clinicians using two measures of voice signal irregularity: the jitter (J) and the coefficient of variation of the fundamental frequency (F0CV). The purpose is also to test to what extent of irregularity trained raters are capable of determining visually the glottal cycle length as compared to dedicated software tools. For a perfect control of the amount of jitter and noise put in, data consist of synthesized sustained vowels corrupted by increasing jitter and noise. Both jitter and noise can be varied to the desired extent according to built-in functions. All the tools give almost reliable measurements up to 15% of jitter, for low or moderate noise, while only few of them are reliable for higher jitter and noise levels and would thus be suited for perturbation measures in strongly irregular voice signals. As shown in Part I of this work, for low noise levels the results obtained by visual inspection from expert raters are comparable or better than those obtained with the tools presented here, at the expense of a larger amount of time devoted to searching visually for the glottal cycle lengths in the signal waveform. In this paper it is shown that results rapidly deteriorate with increasing noise. Hence, the use of a robust tool for voice analysis can give valid support to clinicians in term of reliability, reproducibility of results, and time-saving.

Validity of jitter measures in non-quasi-periodic voices. Part I: perceptual and computer performances in cycle pattern recognition.

The limit of about 5% for reliable quantification of jitter in sustained vowels of dysphonic voices-a widely accepted guideline-deserves critical analysis. The present study pertains to the effect of experience and training on the perceptual (visual) capability of correctly identifying periods in (highly) perturbed signals, and to a comparison of the performance of several programs for voice analysis. Synthesized realistic vowels (/a:/) with exactly known jitter (2.7%-31.5%) are used as material. After selection and training, experienced raters demonstrate excellent agreement in correctly identifying periods up to high values of jitter put in. Perceptual rating outperforms all computer programs in accuracy. Most remain reliable up to 10% jitter; one of them correctly measures up to the highest level.

Estimation of vocal dysperiodicities in disordered connected speech by means of distant-sample bidirectional linear predictive analysis.

The article presents an analysis of vocal dysperiodicities in connected speech produced by dysphonic speakers. The processing is based on a comparison of the present speech fragment with future and past fragments. The size of the dysperiodicity estimate is zero for periodic speech signals. A feeble increase of the vocal dysperiodicity is guaranteed to produce a feeble increase of the estimate. No spurious noise boosting occurs owing to cycle insertion and omission errors, or phonetic segment boundary artifacts. Additional objectives of the study have been investigating whether deviations from periodicity are larger or more commonplace in connected speech than in sustained vowels, and whether sentences that comprise frequent voice onsets and offsets are noisier than sentences that comprise few. The corpora contain sustained vowels as well as grammatically- and phonetically matched sentences. An acoustic marker that correlates with the perceived degree of hoarseness summarizes the size of the dysperiodicities. The marker values for sustained vowels have been highly correlated with those for connected speech, and the marker values for sentences that comprise few voiced/unvoiced transients have been highly correlated with the marker values for sentences that comprise many.

Modulation frequency and modulation level owing to vocal microtremor.

Vocal microtremor designates a normal slow modulation of the vocal cycle lengths of speakers who do not suffer from pathological tremor of the limbs and whose voices are not perceived as tremulous. Vocal microtremor is therefore distinct from pathological vocal tremor. The objective is to report data about the modulation frequency and modulation level owing to vocal microtremor. The modulation data have been obtained for vowels [a], [i], and [u] sustained by normophonic and mildly dysphonic male and female speakers. The results are the following. First, modulation frequencies and relative modulation levels do not differ significantly for male and female speakers, normophonic and mildly dysphonic speakers, as well as for vowel timbres [a], [i], and [u]. Second, the typical interquartile intervals of the modulation frequency and modulation level are equal to 2.0-4.7 Hz and 0.4%-1.3%, respectively. Third, dissimilarities between data reported by different studies are due to different cutoff frequencies below which spectral peaks are considered not to contribute to vocal microtremor.

Spectral models of additive and modulation noise in speech and phonatory excitation signals.

The article presents spectral models of additive and modulation noise in speech. The purpose is to learn about the causes of noise in the spectra of normal and disordered voices and to gauge whether the spectral properties of the perturbations of the phonatory excitation signal can be inferred from the spectral properties of the speech signal. The approach to modeling consists of deducing the Fourier series of the perturbed speech, assuming that the Fourier series of the noise and of the clean monocycle-periodic excitation are known. The models explain published data, take into account the effects of supraglottal tremor, demonstrate the modulation distortion owing to vocal tract filtering, establish conditions under which noise cues of different speech signals may be compared, and predict the impossibility of inferring the spectral properties of the frequency modulating noise from the spectral properties of the frequency modulation noise (e.g., phonatory jitter and frequency tremor). The general conclusion is that only phonatory frequency modulation noise is spectrally relevant. Other types of noise in speech are either epiphenomenal, or their spectral effects are masked by the spectral effects of frequency modulation noise.

Shaping function models of the phonatory excitation signal.

The phonatory excitation signal is the acoustic signal that is generated at the glottis by the vibrating vocal folds and pulsatile airflow. A shaping function model is a nonlinear memoryless input-output characteristic that transforms a simple harmonic into the desired output. The model can be fitted linearly to observed or simulated template cycles. The instantaneous values of the excitation cycle centroid, amplitude as well as length, and the cues for phonatory identity are set via distinct parameters. The synthetic phonatory excitation signal is zero on average, as well as identically zero when the glottal airflow rate is constant.