Three-dimensional vocal tract imaging and formant structure: varying vocal register, pitch, and loudness

Analysis of Glottal Inverse Filtering in the Presence of Source-Filter Interaction

The validity of glottal inverse filtering (GIF) to obtain a glottal flow waveform from radiated pressure signal in the presence and absence of source-filter interaction was studied systematically. A driven vocal fold surface model of vocal fold vibration was used to generate source signals. A one-dimensional wave reflection algorithm was used to solve for acoustic pressures in the vocal tract. Several test signals were generated with and without source-filter interaction at various fundamental frequencies and vowels. Linear Predictive Coding (LPC), Quasi Closed Phase (QCP), and Quadratic Programming (QPR) based algorithms, along with supraglottal impulse response, were used to inverse filter the radiated pressure signals to obtain the glottal flow pulses. The accuracy of each algorithm was tested for its recovery of maximum flow declination rate (MFDR), peak glottal flow, open phase ripple factor, closed phase ripple factor, and mean squared error. The algorithms were also tested for their absolute relative errors of the Normalized Amplitude Quotient, the Quasi-Open Quotient, and the Harmonic Richness Factor. The results indicated that the mean squared error decreased with increase in source-filter interaction level suggesting that the inverse filtering algorithms perform better in the presence of source-filter interaction. All glottal inverse filtering algorithms predicted the open phase ripple factor better than the closed phase ripple factor of a glottal flow waveform, irrespective of the source-filter interaction level. Major prediction errors occurred in the estimation of the closed phase ripple factor, MFDR, peak glottal flow, normalized amplitude quotient, and Quasi-Open Quotient. Feedback-related nonlinearity (source-filter interaction) affected the recovered signal primarily when f o was well below the first formant frequency of a vowel. The prediction error increased when f o was close to the first formant frequency due to the difficulty of estimating the precise value of resonance frequencies, which was exacerbated by nonlinear kinetic losses in the vocal tract.

Relevance of the Implementation of Teeth in Three-Dimensional Vocal Tract Models

PURPOSE

Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics.

METHOD

The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (fRn). The fRn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing.

RESULTS

Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs.

CONCLUSIONS

To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.5386771.

Sonographic Dynamic Description of the Laryngeal Tract: Definition of Quantitative Measures to Characterize Vocal Fold Motion and Estimation of Their Normal Values

Vocal fold motion was analyzed during free breathing using two-dimensional dynamic ultrasound imaging. Two cadavers were first analyzed to define easily identifiable landmarks. Motion of the laryngeal tract was then analyzed in an axial plane. Left and right arytenoids and thyroid cartilage were defined on images corresponding to abduction and adduction of the laryngeal tract. Associated area measurements were established for 50 healthy subjects. All area indices were significantly larger during abduction than adduction. Symmetry of motion was established by comparing each hemi-larynx, and mobility fractions were defined. Normal values of laryngeal motion during free breathing were thus established.

Correlation Between the Position of the Hyoid Bone on Lateral Cephalographs and Formant Frequencies

OBJECTIVES

The objective of this study is to examine the F1, F2, F3, and F4 during sustained vowels /ɑ/, /i/, /o/, /u/.

STUDY DESIGN

Prospective cross-sectional study.

METHODS

Fifty-two consecutive patients aged between 9 years and 38 years were invited to participate in this study. Linear measurements included linear vertical distance from the hyoid bone to the sella turcica (H-S); linear vertical distance from the hyoid bone to the posterior nasal spine (H-PNS); linear measure from the hyoid bone to the most anterior point of the cervical vertebra C3 (H-C3); and linear vertical distance from the hyoid bone to the mandibular plane (H-MP).

RESULTS

The results showed a moderate and statistically significant correlation between the average fundamental frequency for the vowel /ɑ/ and H-C3, H-S, and H-PNS and another moderate negative correlation between F3 and F4, and the vertical position of the hyoid bone H-C3 and H-S. For the vowel /i/, there was a moderate negative correlation between F1, F3, and F4 and H-S and also a moderate negative correlation between F3 and F4 and H-C3. For the vowel /o/, there was a moderate negative correlation between F4 and H-S and H-PNS. For the vowel /u/, only F4 correlated significantly with H-S.

CONCLUSION

There is a moderate correlation between the high formants, mostly F4, and the cephalo-caudal position of the hyoid bone.

The effect of increased vocal intensity on interarticulator timing in speakers with Parkinson’s disease: a preliminary analysis

PURPOSE

The purpose of the current study was to investigate the effect of increased vocal intensity on interarticulator timing in individuals with Parkinson's disease (PD).

METHODS

Ten individuals with mild to moderate hypophonia, secondary to PD, were selected for study. Over an 8-week treatment period, multi-talker babble noise was presented monaurally to the individuals with PD during everyday communication contexts to elicit increased vocal intensity (Lombard effect). Outcome measures included sound pressure level (SPL), voice onset time (VOT), VOT ratio, percent voicing, and speech intelligibility.

RESULTS

Group and individual participant responses to the treatment are reported and discussed. Speakers with PD were shown to significantly increase SPL in response to treatment. Six of the 10 speakers showed improved temporal coordination between the laryngeal and supralaryngeal mechanisms (interarticulator timing) in response to treatment. Four of the 10 speakers, however, showed reduced laryngeal–supralaryngeal timing at the end of treatment. Group speech intelligibility scores were significantly higher post-treatment as compared to pre-treatment.

CONCLUSIONS

Voice treatment during everyday communication resulted in improved temporal coordination across the laryngeal and supralaryngeal mechanisms for the majority of speakers with PD and made them easier to understand. Further investigations are planned to explore individual differences in response to treatment. The identification of speaker-specific voicing and devoicing strategies is consistent with the heterogeneous nature of PD.

LEARNING OUTCOMES

Readers will be able to: 1. Describe the speech and voice characteristics of individuals with Parkinson's disease. 2. Define the Lombard effect. 3. Describe acoustic measures of voice onset time and percent voicing. 4. Describe the effect of voice treatment on voice onset time and percent voicing in individuals with Parkinson's disease.

Emotions in freely varying and mono-pitched vowels, acoustic and EGG analyses

Vocal emotions are expressed either by speech or singing. The difference is that in singing the pitch is predetermined while in speech it may vary freely. It was of interest to study whether there were voice quality differences between freely varying and mono-pitched vowels expressed by professional actors. Given their profession, actors have to be able to express emotions both by speech and singing. Electroglottogram and acoustic analyses of emotional utterances embedded in expressions of freely varying vowels [a:], [i:], [u:] (96 samples) and mono-pitched protracted vowels (96 samples) were studied. Contact quotient (CQEGG) was calculated using 35%, 55%, and 80% threshold levels. Three different threshold levels were used in order to evaluate their effects on emotions. Genders were studied separately. The results suggested significant gender differences for CQEGG 80% threshold level. SPL, CQEGG, and F4 were used to convey emotions, but to a lesser degree, when F0 was predetermined. Moreover, females showed fewer significant variations than males. Both genders used more hypofunctional phonation type in mono-pitched utterances than in the expressions with freely varying pitch. The present material warrants further study of the interplay between CQEGG threshold levels and formant frequencies, and listening tests to investigate the perceptual value of the mono-pitched vowels in the communication of emotions.

Vocal tract area functions and formant frequencies in opera tenors' modal and falsetto registers

According to recent model investigations, vocal tract resonance is relevant to vocal registers. However, no experimental corroboration of this claim has been published so far. In the present investigation, ten professional tenors' vocal tract configurations were analyzed using MRI volumetry. All subjects produced a sustained tone on the pitch F4 (349 Hz) on the vowel /a/ (1) in modal and (2) in falsetto register. The area functions were estimated from the MRI data and their associated formant frequencies were calculated. In a second condition the same subjects repeated the same tasks in a sound treated room and their formant frequencies were estimated by means of inverse filtering. In both recordings similar formant frequencies were observed. Vocal tract shapes differed between modal and falsetto register. In modal as compared to falsetto the lip opening and the oral cavity were wider and the first formant frequency was higher. In this sense the presented results are in agreement with the claim that the formant frequencies differ between registers.

Vocal tract configurations in male alto register functions

PURPOSE

Professional male altos (countertenors) mostly use a register function, which is considered to be derived from falsetto. However, the sound produced differs in professional altos compared with the modal register or falsetto of untrained voices. The aim of this study was to analyze differences of the vocal tract shapes in male alto register functions.

MATERIAL AND METHODS

Dynamic real-time magnetic resonance imaging of eight frames per second was used to analyze the vocal tract profile in seven professional male altos who sang on the vowel /a/, an ascending and descending scale from G3 (196 Hz) to E4 (330 Hz). The scale included their register transition from modal register to stage (counter) falsetto and naïve falsetto.

RESULTS

Register transitions from modal register to stage falsetto were associated with increased lip opening, jaw retraction, elevation and back positioning of the tongue, pharynx narrowing, uvula elevation, drop of larynx height, and tilting of the larynx. Differences between stage and naïve falsetto were found mostly with regard to lip opening and pharynx width.

CONCLUSIONS

The differences between the vocal tract configurations might have an impact on the acoustic characteristics observed in professional male alto register functions.

Vocal tract analysis in patients with vocal fold nodules, clefts and cysts

The supraglottic plan represents an important dimension in vocal production, and its characterization is very important in the evaluation and treatment approach of dysphonic individuals.

Aim

to check if certain glottic configurations are related to specific adjustments in the vocal tract. To use nasal and laryngeal fibroscopy to assess the frequency of supraglottic vocal tract adjustments in dysphonic women with nodules, clefts and cysts.

Methods

We assessed 31 dysphonic women, with age ranging between 18 and 45 years, with vocal alteration and a diagnosis of nodules, middle-posterior cleft and cyst, and we carried out a summarized evaluation of the sensory-motor and oral systems and the patients were submitted to video-laryngostroboscopy and nasal and laryngeal fibroscopy. Three distinct groups were selected: patients with bilateral nodules, clefts and cysts, with similar glottic configuration. Their vocal tracts were visually analyzed through exams of nasal and laryngeal fibroscopy, by speech and hearing therapists and otorhinolaryngologists, checking the following parameters: supraglottic constriction, larynx vertical mobility, pharyngeal constriction and tongue mobility. The data was statistically described and treated.

Results

during visual analysis we did not find statistically significant differences which would separate the glottic alterations groups.

Conclusion

There was no correlation between supraglottic tract adjustments with any particular type of glottic alteration. These are individual behaviors that generate adjustments and justify the different vocal qualities in patients with the same type of laryngeal alteration.

Metallic Voice: Physiological and Acoustic Features

The metallic voice is usually confused with ring or nasality by singers and nontrained listeners, who are not used to perceptual vocal analysis. They believe a metallic voice results from a rise in fundamental frequency. A diagnostic error in this aspect may lead to lowering pitch, an incorrect procedure that could cause vocal overload and fatigue. The purpose of this article is to study the quality of metallic voice considering the correlation between information of the physiological and acoustic plans, based on a perceptive consensual assumption. Fiberscopic video pharyngolaryngoscopy was performed on 21 professional singers while speaking vowel [e]--in normal and metallic modes to observe muscular movements and structural changes of the velopharynx, pharynx, and larynx. Vocal samples captured simultaneously to the fiberscopic examination were acoustically analyzed. Frequency and amplitude of the first four formants (F(1), F(2), F(3), and F(4)) were extracted by means of linear predictor coefficients (LPC) spectrum and were statistically analyzed. Vocal tract adjustments such as velar lowering, pharyngeal wall narrowing, laryngeal rise, aryepiglottic, and lateral laryngeal constrictions were frequently found; there were no significant changes in frequency and amplitude of F(1) in the metallic voice; there were significant increases in amplitudes of F(2), F(3), and F(4) and in frequency for F(2); metallic voice perceived as louder was correlated to an increase in amplitude of F(3) and F(4). Physiological adjustments of velopharynx, pharynx, and larynx are combined in characterizing the metallic voice and can be acoustically related to changes in formant pattern.

The influence of epilarynx area on vocal fold dynamics

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.

Volumetric measurements of vocal tracts for male speakers from different races

Research examining physiologic and acoustic characteristics of culturally diverse populations is sorely needed, but rarely reported. The major aim of this study was to quantify vocal tract dimensional parameters (oral length, oral volume, pharyngeal length, pharyngeal volume, total vocal tract length and total vocal tract volume) of adult male speakers from three different racial populations (White American, African American, and Chinese). It also attempted to investigate if volumetric differences in the speakers' vocal tracts, like length differences, would contribute to the acoustic characteristics of these speakers from different races. The findings of this study support the hypothesis that speakers from different races may have morphological differences in their vocal tract dimensions, and these morphological differences (especially volumetric differences) could be partially responsible for the formant frequency differences in a vowel sound void of specific language/dialectal impacts. The study has provided speech scientists, speech-language pathologists, linguists and other health professionals with a new and preliminary acoustic and physiological database for adult male speakers from these three different races.

Normative standards for vocal tract dimensions by race as measured by acoustic pharyngometry

SUMMARY

Acoustic pharyngometry evaluates the geometry of the vocal tract with acoustic reflections and provides information about vocal tract cross-sectional area and volume from lip to the glottis. Variations in vocal tract diameters are needed for speech scientists to validate various acoustic models and for medical professionals since the advent of endoscopic surgical techniques. Race is known to be one of the most important factors affecting the oral and nasal structures. This study compared vocal tract dimensions of White American, African American, and Chinese male and female speakers. One hundred and twenty healthy adult subjects with equal numbers of men and women were divided among three races. Subjects were controlled for age, gender, height, and weight. Six dimensional parameters of the speakers' vocal tract cavities were measured with acoustic reflection technology (AR). Significant gender and race main effects were found in certain vocal tract dimensions. The findings of this study now provide speech scientists, speech-language pathologists, and other health professionals with a new anatomical database of vocal tract variations for adult speakers from three different races.

Evaluation of cross-section airway configuration of obstructive sleep apnea

Upper airway imaging techniques can be useful to identify the exact location and nature of the obstruction in obstructive sleep apnea (OSA) patients. Ten OSA patients and 10 non-OSA control subjects were imaged using cone-beam computed tomography (NewTom QR-DVT9000) to compare their upper airway structure. The OSA subjects presented higher BMI (OSA: 29.5 +/- 9.05 kg/m(2); non-OSA: 23.1 +/- 3.05 kg/m(2) [P = .034]), lower total volume (mm(3)) of the airway (OSA: 4868.4 +/- 1863.9; non-OSA: 6051.7 +/- 1756.4 [P = .054]), statistically significantly smaller anterior-posterior dimension (mm) of the minimum cross-section segment (OSA: 4.6 +/- 1.2; non-OSA: 7.8 +/- 3.31 [P = .009]), and smaller minimum cross-section area (OSA: 45.8+/-17.5 mm(2); non-OSA: 146.9 +/- 111.7 mm(2) [P = .011]) positioned below the occlusal plane in 70% of the cases (OSA:7 out of 10; non-OSA: 5 out of 10 [P = .030]). The OSA group presented a concave or elliptic shaped airway and the non-OSA group presented a concave, round, or square shaped airway.

Changes in the human vocal tract due to aging and the acoustic correlates of speech production: a pilot study

This investigation used a derivation of acoustic reflection (AR) technology to make cross-sectional measurements of changes due to aging in the oral and pharyngeal lumina of male and female speakers. The purpose of the study was to establish preliminary normative data for such changes and to obtain acoustic measurements of changes due to aging in the formant frequencies of selected spoken vowels and their long-term average spectra (LTAS) analysis. Thirty-eight young men and women and 38 elderly men and women were involved in the study. The oral and pharyngeal lumina of the participants were measured with AR technology, and their formant frequencies were analyzed using the Kay Elemetrics Computerized Speech Lab. The findings have delineated specific and similar patterns of aging changes in human vocal tract configurations in speakers of both genders. Namely, the oral cavity length and volume of elderly speakers increased significantly compared to their young cohorts. The total vocal tract volume of elderly speakers also showed a significant increment, whereas the total vocal tract length of elderly speakers did not differ significantly from their young cohorts. Elderly speakers of both genders also showed similar patterns of acoustic changes of speech production, that is, consistent lowering of formant frequencies (especially F1) across selected vowel productions. Although new research models are still needed to succinctly account for the speech acoustic changes of the elderly, especially for their specific patterns of human vocal tract dimensional changes, this study has innovatively applied the noninvasive and cost-effective AR technology to monitor age-related human oral and pharyngeal lumina changes that have direct consequences for speech production.

Vocal intensity in falsetto phonation of a countertenor: an analysis by synthesis approach

An analysis by synthesis paradigm was implemented to model glottal airflow and vocal tract acoustics for the falsetto phonation of a trained countertenor. Changes in vocal intensity were measured as a function of subglottal pressure, open quotient of the time-varying glottal airflow pulse, and formant tuning. The contributions of laryngeal adduction (open quotient of the glottal flow pulse) and of formant tuning to intensity change were derived from modeled data. The findings were: (1) Subglottal pressure accounted for almost 90% of the variation in SPL in falsetto phonation. (2) The open quotient of the glottal flow pulse was remarkably constant in these falsetto phonations, and thus did not affect vocal intensity significantly. (3) Formant tuning occurred in two out of nine possibilities for the vowel /a/. These instances did not support the concept of systematic exploitation of formant tuning.