Publications

    M. Motie-Shirazi, et al., “Toward development of a vocal fold contact pressure probe: Sensor characterization and validation using synthetic vocal fold models,” Applied Sciences, vol. 9, no. 15, pp. 3002, 2019. Publisher's VersionAbstract
    Excessive vocal fold collision pressures during phonation are considered to play a primary role in the formation of benign vocal fold lesions, such as nodules. The ability to accurately and reliably acquire intraglottal pressure has the potential to provide unique insights into the pathophysiology of phonotrauma. Difficulties arise, however, in directly measuring vocal fold contact pressures due to physical intrusion from the sensor that may disrupt the contact mechanics, as well as difficulty in determining probe/sensor position relative to the contact location. These issues are quantified and addressed through the implementation of a novel approach for identifying the timing and location of vocal fold contact, and measuring intraglottal and vocal fold contact pressures via a pressure probe embedded in the wall of a hemi-laryngeal flow facility. The accuracy and sensitivity of the pressure measurements are validated against ground truth values. Application to in vivo approaches are assessed by acquiring intraglottal and VF contact pressures using a synthetic, self-oscillating vocal fold model in a hemi-laryngeal configuration, where the sensitivity of the measured intraglottal and vocal fold contact pressure relative to the sensor position is explored.
    J. A. Whitfield, Z. Kriegel, A. M. Fullenkamp, and D. D. Mehta, “Effects of concurrent manual task performance on connected speech acoustics in individuals with Parkinson disease,” Journal of Speech, Language, and Hearing Research, vol. 62, no. 7, pp. 2099–2117, 2019. Publisher's VersionAbstract
    Purpose: Prior investigations suggest that simultaneous
    performance of more than 1 motor-oriented task may
    exacerbate speech motor deficits in individuals with
    Parkinson disease (PD). The purpose of the current
    investigation was to examine the extent to which
    performing a low-demand manual task affected the
    connected speech in individuals with and without PD.
    Method: Individuals with PD and neurologically healthy
    controls performed speech tasks (reading and
    extemporaneous speech tasks) and an oscillatory
    manual task (a counterclockwise circle-drawing
    task) in isolation (single-task condition) and concurrently
    (dual-task condition).
    Results: Relative to speech task performance, no changes
    in speech acoustics were observed for either group when
    the low-demand motor task was performed with the
    concurrent reading tasks. Speakers with PD exhibited
    a significant decrease in pause duration between the
    single-task (speech only) and dual-task conditions
    for the extemporaneous speech task, whereas control
    participants did not exhibit changes in any speech
    production variable between the single- and dual-task
    conditions.
    Conclusions: Overall, there were little to no changes in
    speech production when a low-demand oscillatory motor
    task was performed with concurrent reading. For the
    extemporaneous task, however, individuals with PD
    exhibited significant changes when the speech and manual
    tasks were performed concurrently, a pattern that was
    not observed for control speakers.
    Supplemental Material: https://doi.org/10.23641/asha.
    8637008
    J. A. Whitfield and D. D. Mehta, “Examination of clear speech in Parkinson disease using passage-level vowel space metrics,” Journal of Speech, Language, and Hearing Research, vol. 62, no. 7, pp. 2082–2098, 2019. Publisher's VersionAbstract
    Purpose: The purpose of the current study was to characterize
    clear speech production for speakers with and without
    Parkinson disease (PD) using several measures of working
    vowel space computed from frequently sampled formant
    trajectories.
    Method: The 1st 2 formant frequencies were tracked for
    a reading passage that was produced using habitual and
    clear speaking styles by 15 speakers with PD and 15 healthy
    control speakers. Vowel space metrics were calculated
    from the distribution of frequently sampled formant frequency
    tracks, including vowel space hull area, articulatory–acoustic
    vowel space, and multiple vowel space density (VSD)
    measures based on different percentile contours of the
    formant density distribution.
    Results: Both speaker groups exhibited significant
    increases in the articulatory–acoustic vowel space and
    VSD10, the area of the outermost (10th percentile)
    contour of the formant density distribution, from habitual
    to clear styles. These clarity-related vowel space increases
    were significantly smaller for speakers with PD than
    controls. Both groups also exhibited a significant increase
    in vowel space hull area; however, this metric was not
    sensitive to differences in the clear speech response
    between groups. Relative to healthy controls, speakers
    with PD exhibited a significantly smaller VSD90, the area
    of the most central (90th percentile), densely populated
    region of the formant space.
    Conclusions: Using vowel space metrics calculated from
    formant traces of the reading passage, the current work
    suggests that speakers with PD do indeed reach the more
    peripheral regions of the vowel space during connected
    speech but spend a larger percentage of the time in more
    central regions of formant space than healthy speakers.
    Additionally, working vowel space metrics based on the
    distribution of formant data suggested that speakers with
    PD exhibited less of a clarity-related increase in formant
    space than controls, a trend that was not observed for
    perimeter-based measures of vowel space area.
    J. P. Cortés, et al., “Ambulatory assessment of phonotraumatic vocal hyperfunction using glottal airflow measures estimated from neck-surface acceleration,” PLoS One, vol. 13, no. 12, pp. e0209017, 2018. Publisher's VersionAbstract
    Phonotraumatic vocal hyperfunction (PVH) is associated with chronic misuse and/or abuse of voice that can result in lesions such as vocalfold nodules. The clinical aerodynamic assessment of vocal function has been recently shown to differentiate between patients with PVH and healthy controls to provide meaningful insight into pathophysiological mechanisms associated with these disorders. However, all current clinical assessment of PVH is incomplete because of its inability to objectively identify the type and extent of detrimental phonatory function that is associated with PVH during daily voice use. The current study sought to address this issue by incorporating, for the first time in a comprehensive ambulatory assessment, glottal airflow parameters estimated from a neck-mounted accelerometer and recorded to a smartphone-based voice monitor. We tested this approach on 48 patients with vocal fold nodules and 48 matched healthy-control subjects who each wore the voice monitor for a week. Seven glottal airflow features were estimated every 50 ms using an impedance-based inverse filtering scheme, and seven high-order summary statistics of each feature were computed every 5 minutes over voiced segments. Based on a univariate hypothesis testing, eight glottal airflow summary statistics were found to be statistically different between patient and healthy-control groups. L1-regularized logistic regression for a supervised classification task yielded a mean (standard deviation) area under the ROC curve of 0.82 (0.25) and an accuracy of 0.83 (0.14). These results outperform the state-of-the-art classification for the same classification task and provide a new avenue to improve the assessment and treatment of hyperfunctional voice disorders.
    V. M. Espinoza, M. Zañartu, J. H. Van Stan, D. D. Mehta, and R. E. Hillman, “Glottal aerodynamic measures in adult females with phonotraumatic and non-phonotraumatic vocal hyperfunction,” Journal of Speech, Language, and Hearing Research, vol. 60, no. 8, pp. 2159-2169, 2017. Publisher's VersionAbstract

     

    PURPOSE:

    The purpose of this study was to determine the validity of preliminary reports showing that glottal aerodynamic measures can identify pathophysiological phonatory mechanisms for phonotraumatic and nonphonotraumatic vocal hyperfunction, which are each distinctly different from normal vocal function.

    METHOD:

    Glottal aerodynamic measures (estimates of subglottal air pressure, peak-to-peak airflow, maximum flow declination rate, and open quotient) were obtained noninvasively using a pneumotachograph mask with an intraoral pressure catheter in 16 women with organic vocal fold lesions, 16 women with muscle tension dysphonia, and 2 associated matched control groups with normal voices. Subjects produced /pae/ syllable strings from which glottal airflow was estimated using inverse filtering during /ae/ vowels, and subglottal pressure was estimated during /p/ closures. All measures were normalized for sound pressure level (SPL) and statistically tested for differences between patient and control groups.

    RESULTS:

    All SPL-normalized measures were significantly lower in the phonotraumatic group as compared with measures in its control group. For the nonphonotraumatic group, only SPL-normalized subglottal pressure and open quotient were significantly lower than measures in its control group.

    CONCLUSIONS:

    Results of this study confirm previous hypotheses and preliminary results indicating that SPL-normalized estimates of glottal aerodynamic measures can be used to describe the different pathophysiological phonatory mechanisms associated with phonotraumatic and nonphonotraumatic vocal hyperfunction.

     

    Purpose

    To determine the validity of preliminary reports showing that glottal aerodynamic measures can identify pathophysiological phonatory mechanisms for phonotraumatic and non-phonotraumatic vocal hyperfunction that are each distinctly different from normal vocal function.

    Method

    Glottal aerodynamic measures (estimates of subglottal air pressure, peak-to-peak airflow, maximum flow declination rate, and open quotient) were obtained non-invasively using a pneumotachograph mask with intra-oral pressure catheter in 16 adult females with organic vocal fold lesions, 16 adult females with muscle tension dysphonia, and two associated matched control groups with normal voices. Subjects produced /pae/ syllable strings from which glottal airflow was estimated using inverse filtering during /ae/ vowels, and subglottal pressure was estimated during /p/ closures. All measures were normalized for sound pressure level (SPL) and statistically tested for differences between patient and control groups.

    Results

    All SPL-normalized measures were significantly lower in the phonotraumatic group as compared to measures in its control group. For the non-phonotraumatic group, only SPL-normalized subglottal pressure and open quotient were significantly lower than measures in its control group.

    Conclusions

    Results of this study confirm previous hypotheses and preliminary results indicating that SPL-normalized estimates of glottal aerodynamic measures can be used to describe the different pathophysiological phonatory mechanisms associated with phonotraumatic and non-phonotraumatic vocal hyperfunction.
    Y. - R. Chien, D. D. Mehta, Jón Guðnason, M. Zañartu, and T. F. Quatieri, “Evaluation of glottal inverse filtering algorithms using a physiologically based articulatory speech synthesizer,” IEEE/ACM Transactions on Audio, Speech, and Language Processing, vol. 25, no. 8, pp. 1718-1730, 2017. Publisher's VersionAbstract
    Glottal inverse filtering aims to estimate the glottal airflow signal from a speech signal for applications such as speaker recognition and clinical voice assessment. Nonetheless, evaluation of inverse filtering algorithms has been  challenging due to the practical difficulties of directly measuring glottal airflow. Apart from this, it is acknowledged that the performance of many methods degrade in voice conditions that are of great interest, such as breathiness, high pitch, soft voice, and running speech. This paper presents a comprehensive, objective, and comparative evaluation of state-of-the-art inverse filtering algorithms that takes advantage of speech and glottal airflow signals generated by a physiological speech synthesizer. The synthesizer provides a physics-based simulation of the voice production process and thus an adequate test bed for revealing the temporal and spectral performance characteristics of each algorithm. Included in the synthetic data are continuous speech utterances and sustained vowels, which are produced with multiple voice qualities (pressed, slightly pressed, modal, slightly breathy, and breathy), fundamental frequencies, and subglottal pressures to simulate the natural variations in real speech. In evaluating the accuracy of a glottal flow estimate, multiple error measures are used, including an error in the estimated signal that measures overall waveform deviation, as well as an error in each of several clinically relevant features extracted from the glottal flow estimate. Waveform errors calculated from glottal flow estimation experiments exhibited mean values around 30% for sustained vowels, and around 40% for continuous speech, of the amplitude of true glottal flow derivative. Closed-phase approaches showed remarkable stability across different voice qualities and subglottal pressures. The algorithms of choice, as suggested by significance tests, are closed-phase covariance analysis for the analysis of sustained vowels, and sparse linear prediction for the analysis of continuous speech. Results of data subset analysis suggest that analysis of close rounded vowels is an additional challenge in glottal flow estimation.
    A. S. Fryd, J. H. Van Stan, R. E. Hillman, and D. D. Mehta, “Estimating subglottal pressure from neck-surface acceleration during normal voice production,” Journal of Speech, Language, and Hearing Research, vol. 59, no. 6, pp. 1335-1345, 2016. Publisher's VersionAbstract

    Purpose The purpose of this study was to evaluate the potential for estimating subglottal air pressure using a neck-surface accelerometer and to compare the accuracy of predicting subglottal air pressure relative to predicting acoustic sound pressure level (SPL).

    Method Indirect estimates of subglottal pressure (Psg′) were obtained from 10 vocally healthy speakers during loud-to-soft repetitions of 3 different /p/–vowel gestures (/pa/, /pi/, /pu/) at 3 pitch levels in the modal register. Intraoral air pressure, neck-surface acceleration, and radiated acoustic pressure were recorded, and the root-mean-square amplitude of the acceleration signal was correlated with Psg′ and SPL.

    Results The coefficient of determination between accelerometer level and Psg′ was high when data were pooled from all vowel and pitch contexts for each participant (r 2 = .68–.93). These relationships were stronger than corresponding relationships between accelerometer level and SPL (r 2 = .46–.81). The average 95% prediction interval for estimating Psg′ using accelerometer level was ±2.53 cm H2O, ranging from ±1.70 to ±3.74 cm H2O across participants.

    Conclusions Accelerometer signal amplitude correlated more strongly with Psg′ than with SPL. Future work is warranted to investigate the robustness of the relationship in nonmodal voice qualities, individuals with voice disorders, and accelerometer-based ambulatory monitoring of subglottal pressure.

    D. Mehta, J. Van Stan, and R. Hillman, “Relationships between vocal function measures derived from an acoustic microphone and a subglottal neck-surface accelerometer,” IEEE/ACM Transactions on Audio, Speech, and Language Processing, vol. 24, no. 4, pp. 659-668, 2016. Publisher's VersionAbstract

    Monitoring subglottal neck-surface acceleration has received renewed attention due to the ability of low-profile accelerometers to confidentially and noninvasively track properties related to normal and disordered voice characteristics and behavior. This study investigated the ability of subglottal necksurface acceleration to yield vocal function measures traditionally derived from the acoustic voice signal and help guide the development of clinically functional accelerometer-based measures from a physiological perspective. Results are reported for 82 adult speakers with voice disorders and 52 adult speakers with normal voices who produced the sustained vowels /A/, /i/, and /u/ at a comfortable pitch and loudness during the simultaneous recording of radiated acoustic pressure and subglottal necksurface acceleration. As expected, timing-related measures of jitter exhibited the strongest correlation between acoustic and necksurface acceleration waveforms (r 0:99), whereas amplitudebased measures of shimmer correlated less strongly (r 0:74). Additionally, weaker correlations were exhibited by spectral measures of harmonics-to-noise ratio (r 0:69) and tilt (r 0:57), whereas the cepstral peak prominence correlated more strongly (r 0:90). These empirical relationships provide evidence to support the use of accelerometers as effective complements to acoustic recordings in the assessment and monitoring of vocal function in the laboratory, clinic, and during an individual’s daily activities.

    Y. - A. S. Lien, et al., “Voice relative fundamental frequency via neck-skin acceleration in individuals with voice disorders,” Journal of Speech, Language, and Hearing Research, vol. 58, no. 5, pp. 1482-1487, 2015. Publisher's VersionAbstract

    Abstract Purpose: This study investigated the use of neck-skin acceleration for relative fundamental frequency (RFF) analysis. Method: Forty individuals with voice disorders associated with vocal hyperfunction and 20 age- and sex-matched control participants were recorded with a subglottal neck-surface accelerometer and a microphone while producing speech stimuli appropriate for RFF. Rater reliabilities, RFF means, and RFF standard deviations derived from the accelerometer were compared with those derived from the microphone. Results: RFF estimated from the accelerometer had slightly higher intrarater reliability and identical interrater reliability compared with values estimated with the microphone. Although sensor type and the Vocal Cycle × Sensor and Vocal Cycle × Sensor × Group interactions showed significant effects on RFF means, the typical RFF pattern could be derived from either sensor. For both sensors, the RFF of individuals with vocal hyperfunction was lower than that of the controls. Sensor type and its interactions did not have significant effects on RFF standard deviations. Conclusions: RFF can be reliably estimated using an accelerometer, but these values cannot be compared with those collected via microphone. Future studies are needed to determine the physiological basis of RFF and examine the effect of sensors on RFF in practical voice assessment and monitoring settings.

    D. D. Mehta, et al., “Using ambulatory voice monitoring to investigate common voice disorders: Research update,” Frontiers in Bioengineering and Biotechnology, vol. 3, no. 155, pp. 1-14, 2015. Publisher's VersionAbstract

    Many common voice disorders are chronic or recurring conditions that are likely to result from inefficient and/or abusive patterns of vocal behavior, referred to as vocal hyperfunction. The clinical management of hyperfunctional voice disorders would be greatly enhanced by the ability to monitor and quantify detrimental vocal behaviors during an individual’s activities of daily life. This paper provides an update on ongoing work that uses a miniature accelerometer on the neck surface below the larynx to collect a large set of ambulatory data on patients with hyperfunctional voice disorders (before and after treatment) and matched-control subjects. Three types of analysis approaches are being employed in an effort to identify the best set of measures for differentiating among hyperfunctional and normal patterns of vocal behavior: (1) ambulatory measures of voice use that include vocal dose and voice quality correlates, (2) aerodynamic measures based on glottal airflow estimates extracted from the accelerometer signal using subject-specific vocal system models, and (3) classification based on machine learning and pattern recognition approaches that have been used successfully in analyzing long-term recordings of other physiological signals. Preliminary results demonstrate the potential for ambulatory voice monitoring to improve the diagnosis and treatment of common hyperfunctional voice disorders.

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