Vocal Tract Research Articles

Self-reported Vocal symptoms among speech language pathologists dealing with children with hearing impairment and cerebral palsy

A cross-sectional study was conducted at the Ripah International University, Lahore, Pakistan from January to April, 2022 to evaluate and compare the Self-Reported Vocal symptoms among Speech Language Pathologists (SLP) practicing with children having Hearing Impairment (HI) and Cerebral Palsy (CP). The sample included 141 participants of both genders, aged 25 to 60 years, practicing with children with hearing impairment and cerebral palsy for at least one year. Vocal Tract Discomfort Scale (VTDS) and Voice Activity Participation Profile (VAPP) were utilised for data collection which was analysed using SPSS Ver-23. The study revealed no significant association of self-perceived vocal symptoms for SLPs catering to CP and HI children with p=0.303 and p=0.412 for VTDS and VAPP scores respectively and with higher mean scores for SLPs catering to CP children. Results revealed a total VTDS score of 40.26±13.10 with highest score for dryness, while highest VAPP mean score was noted for daily communication (53.82±23.20). Hence, there is no significant association of the speciality being catered to, while dryness is the commonest self-perceived symptom. Keywords: Cerebral Palsy, Hearing Impairment, Self-concept, Speech-Language Pathologist.

Examining the Quasi-Steady Airflow Assumption in Irregular Vocal Fold Vibration

The quasi-steady flow assumption (QSFA) is commonly used in the field of biomechanics of phonation. It approximates time-varying glottal flow with steady flow solutions based on frozen glottal shapes, ignoring unsteady flow behaviors and vocal fold motion. This study examined the limitations of QSFA in human phonation using numerical methods by considering factors of phonation frequency, air inertance in the vocal tract, and irregular glottal shapes. Two sets of irregular glottal shapes were examined through dynamic, pseudo-static, and quasi-steady simulations. The differences between dynamic and quasi-steady/pseudo-static simulations were measured for glottal flow rate, glottal wall pressure, and sound spectrum to evaluate the validity of QSFA. The results show that errors in glottal flow rate and wall pressure predicted by QSFA were small at 100 Hz but significant at 500 Hz due to growing flow unsteadiness. Air inertia in the vocal tract worsened predictions when interacting with unsteady glottal flow. Flow unsteadiness also influenced the harmonic energy ratio, which is perceptually important. The effects of glottal shape and glottal wall motion on the validity of QSFA were found to be insignificant.

An Investigation of Acoustic Back-Coupling in Human Phonation on a Synthetic Larynx Model.

In the human phonation process, acoustic standing waves in the vocal tract can influence the fluid flow through the glottis as well as vocal fold oscillation. To investigate the amount of acoustic back-coupling, the supraglottal flow field has been recorded via high-speed particle image velocimetry (PIV) in a synthetic larynx model for several configurations with different vocal tract lengths. Based on the obtained velocity fields, acoustic source terms were computed. Additionally, the sound radiation into the far field was recorded via microphone measurements and the vocal fold oscillation via high-speed camera recordings. The PIV measurements revealed that near a vocal tract resonance frequency fR, the vocal fold oscillation frequency fo (and therefore also the flow field's fundamental frequency) jumps onto fR. This is accompanied by a substantial relative increase in aeroacoustic sound generation efficiency. Furthermore, the measurements show that fo-fR-coupling increases vocal efficiency, signal-to-noise ratio, harmonics-to-noise ratio and cepstral peak prominence. At the same time, the glottal volume flow needed for stable vocal fold oscillation decreases strongly. All of this results in an improved voice quality and phonation efficiency so that a person phonating with fo-fR-coupling can phonate longer and with better voice quality.

A measure of differences in speech signals by the voice timbre

This research relates to the field of speech technologies, where the key problem is the optimization of speech signal processing under conditions of a priori uncertainty of its fine structure. The task of automatic (objective) analysis of voice timbre using a speech signal of finite duration is considered. It is proposed to use a universal information-theoretic approach to solve it. Based on the Kullback-Leibler divergence, an expression is obtained for the asymptotically optimal decision statistic for distinguishing speech signals by voice timbre. Pointed to an acute problem in its practical implementation, namely: synchronization of the sequence of observations with the main tone of speech signals. To overcome the described problem, an objective measure of timbre differences in speech signals is proposed in terms of the acoustic theory of speech production and its model of the speaker’s vocal tract of the “acoustic trumpet” type. The possibilities of practical implementation of a new measure based on an adaptive recursive are considered. A full-scale experiment was set up and carried out. According to its results, two main properties of the proposed measure were confirmed: high sensitivity to differences in speech signals in terms of voice timbre and, at the same time, invariance with respect to the pitch frequency. The results obtained can be used in the design and research of digital speech processing systems tuned to the speaker’s voice, for example, digital speech transmission systems, biometric, biomedical systems, etc.

Acoustics of Breath Noises in Human Speech: Descriptive and Three-Dimensional Modeling Approaches.

Breathing is ubiquitous in speech production, crucial for structuring speech, and a potential diagnostic indicator for respiratory diseases. However, the acoustic characteristics of speech breathing remain underresearched. This work aims to characterize the spectral properties of human inhalation noises in a large speaker sample and explore their potential similarities with speech sounds. Speech sounds are mostly realized with egressive airflow. To account for this, we investigated the effect of airflow direction (inhalation vs. exhalation) on acoustic properties of certain vocal tract (VT) configurations. To characterize human inhalation, we describe spectra of breath noises produced by human speakers from two data sets comprising 34 female and 100 male participants. To investigate the effect of airflow direction, three-dimensional-printed VT models of a male and a female speaker with static VT configurations of four vowels and four fricatives were used. An airstream was directed through these VT configurations in both directions, and their spectral consequences were analyzed. For human inhalations, we found spectra with a decreasing slope and several weak peaks below 3 kHz. These peaks show moderate (female) to strong (male) overlap with resonances found for participants inhaling with a VT configuration of a central vowel. Results for the VT models suggest that airflow direction is crucial for spectral properties of sibilants, /ç/, and /i:/, but not the other sounds we investigated. Inhalation noise is most similar to /ə/ where airflow direction does not play a role. Inhalation is realized on ingressive airflow, and inhalation noises have specific resonance properties that are most similar to /ə/ but occur without phonation. Airflow direction does not play a role in this specific VT configuration, but subglottal resonances may do. For future work, we suggest investigating the articulation of speech breathing and link it to current work on pause postures. https://doi.org/10.23641/asha.24520585.

The Power of AI-Generated Voices: How Digital Vocal Tract Length Shapes Product Congruency and Ad Performance

Can AI-generated voices be designed to improve product and brand perceptions? Akin to human voices that evoke mental images in a listener even without visual cues, artificially generated voices can be intentionally designed to elicit envisioned mental representations. Drawing from prior work on sound symbolism and computational advances in speech synthesis, the authors explore how the voice of an AI-powered conversational agent (e.g., a voice assistant such as Amazon Alexa) impacts consumer perceptions and choice. Specifically, the authors examine how altering a conversational agent's digital vocal tract length (i.e., timbre) shapes consumers’ physical ascriptions of the agent and subsequent voice–product congruency evaluations. Four experiments, including a large-scale field experiment, demonstrate that increasing (decreasing) the vocal tract length promotes congruency attributions toward stereotypically masculine (feminine) products and improves advertising performance (higher click-through rates and lower costs per click). This article represents a critical first step in deepening understanding on how artificially generated voices shape the consumer experience, demonstrating how firms could enhance product congruency perceptions and advertising performance by leveraging a more theory-driven approach to voice marketing.

Automatic segmentation of vocal tract articulators in real-time magnetic resonance imaging

Background and ObjectivesThe characterization of the vocal tract geometry during speech interests various research topics, including speech production modeling, motor control analysis, and speech therapy design. Real-time MRI is a reliable and non-invasive tool for this purpose. In most cases, it is necessary to know the contours of the individual articulators from the glottis to the lips. Several techniques have been proposed for segmenting vocal tract articulators, but most are limited to specific applications. Moreover, they often do not provide individualized contours for all soft-tissue articulators in a multi-speaker configuration. MethodsA Mask R-CNN network was trained to detect and segment the vocal tract articulator contours in two real-time MRI (RT-MRI) datasets with speech recordings of multiple speakers. Two post-processing algorithms were then proposed to convert the network's outputs into geometrical curves. Nine articulators were considered: the two lips, tongue, soft palate, pharynx, arytenoid cartilage, epiglottis, thyroid cartilage, and vocal folds. A leave-one-out cross-validation protocol was used to evaluate inter-speaker generalization. The evaluation metrics were the point-to-closest-point distance and the Jaccard index (for articulators annotated as closed contours). ResultsThe proposed method accurately segmented the vocal tract articulators, with an average root mean square point-to-closest-point distance of less than 2.2mm for all the articulators in the leave-one-out cross-validation setting. The minimum P2CPRMS was 0.91mm for the upper lip, and the maximum was 2.18mm for the tongue. The Jaccard indices for the thyroid cartilage and vocal folds were 0.60 and 0.61, respectively. Additionally, the method adapted to a new subject with only ten annotated samples. ConclusionsOur research introduced a method for individually segmenting nine non-rigid vocal tract articulators in real-time MRI movies. The software is openly available as an installable package to the speech community. It is designed to develop speech applications and clinical and non-clinical research in fields that require vocal tract geometry, such as speech, singing, and human beatboxing.

An MRI-based articulatory analysis of the Kannada dental-retroflex contrast

AbstractThis paper investigates the production of dental and retroflex stops, fricatives, nasals, and laterals in the Dravidian language Kannada. This is done using articulatory contours extracted from an extensive midsagittal MRI corpus of two female Kannada speakers’ static vocal tract postures intended to capture key aspects of phonemic articulations. Articulatory modelling was used to determine a set of components responsible for the implementation of place and manner contrasts (/t̪ s̪ n̪ l̪/ vs. /ʈ ʂ ɳ ɭ/). These components included both lingual and non-lingual articulatory parameters. Constriction location and length were also determined based on articulatory contours. The results showed that the two speakers produced non-fricative retroflexes with a retracted tongue tip making a constriction behind the alveolar ridge and a characteristic convex tongue shape, yet without a retraction of the posterior portion of the tongue. Apart from the lingual parameters, place differences were also manifested by the vertical position of the larynx (lower for retroflexes). The realisation of the place contrast in sibilant fricatives was different, as /ʂ/ appeared to be produced by both speakers with a laminal alveolopalatal constriction. Manner differences were captured by various non-lingual parameters, yet being also manifested in constriction locations (more anterior for stops). These findings are discussed in the context of previous descriptive and articulatory accounts of dental-retroflex contrasts.

Control of chaotic vibrations in lumped mass models of the vocal folds

Lumped mass models have been widely used as low-dimensional systems to better understand the physics underlying human phonation. This is a highly non-linear process in which subglottal flow emanating from the lungs excite self-oscillations of the vocal folds. Consequently, a pulsating volume velocity is established that produces acoustic waves, which then travel through the vocal tract and are released from the mouth as voice. The self-oscillations of the vocal folds may be affected by many undesirable factors like the presence of polyps, lateral paralyses, excessive subglottal pressure, etc., and transition from regular to chaotic motion. This gives rise to abnormal phonation. In this work, we explore the theoretical possibility of adding smart materials to vocal fold lumped mass models. The smart material must be such that its damping can be dynamically modified. By proper tuning, one can establish a feedback control mechanism that restores chaotic vocal fold oscillations to normality. This would constitute the essence of a pacemaker for phonation.

Spectral warping based data augmentation for low resource children’s speaker verification

In this paper, we present our effort to develop an automatic speaker verification (ASV) system for low resources children’s data. For the children’s speakers, very limited amount of speech data is available in majority of the languages for training the ASV system. Developing an ASV system under low resource conditions is a very challenging problem. To develop the robust baseline system, we merged out of domain adults’ data with children’s data to train the ASV system and tested with children’s speech. This kind of system leads to acoustic mismatches between training and testing data. To overcome this issue, we have proposed spectral warping based data augmentation. We modified adult speech data using spectral warping method (to simulate like children’s speech) and added it to the training data to overcome data scarcity and mismatch between adults’ and children’s speech. The proposed data augmentation gives 20.46% and 52.52% relative improvement (in equal error rate) for Indian Punjabi and British English speech databases, respectively. We compared our proposed method with well known data augmentation methods: SpecAugment, speed perturbation (SP) and vocal tract length perturbation (VTLP), and found that the proposed method performed best. The proposed spectral warping method is publicly available at https://github.com/kathania/Speaker-Verification-spectral-warping.

The effects of vocal tract constrictions on aerodynamic measures in a synthetic vocal fold model.

According to nonlinear source-filter theory, as the strength of the coupling between the source and filter increases, typically by a decrease in the vocal tract cross-sectional area, the resultant increase in the inertance of the vocal tract yields an increase in the interactions between acoustic pressures within the vocal tract and the changing glottal airflow and/or the vibratory pattern of the vocal folds as noted in Titze [(2008). J. Acoust. Soc. Am. 123(4), 1902-1915]. The purpose of the current research was to examine the effects of parametric vocal tract constrictions mimicking epilaryngeal tube and lip narrowing on aerodynamic measures in a dynamic self-oscillating physical model of the vocal folds and vocal tract. Multilayered silicone vocal fold models were created based on Murray and Thomson [(2011). J. Visualized Exp. 58, e3498] and Murray and Thomson [(2012). J. Acoust. Soc. Am. 132(5), 3428-3438] and mounted to a simple synthetic trachea and supraglottal vocal tract model. Four constriction cross-sectional areas were examined at two locations (i.e., at the epilarynx and lip regions). Phonation threshold pressure and flow were measured at phonation onset and offset using four M5-CONV vocal fold models. Results indicated that both constriction magnitude and location are relevant factors in determining glottal aerodynamics. In general, a narrow epilarynx tube or lip constriction resulted in the lowest onset pressures and airflows while the no vocal tract condition resulted in the highest onset pressures and airflows.

Measuring Perceived Voice Disorders and Quality of Life among Female University Teaching Faculty.

Occupations that require heavy vocal use can place the person at risk of voice disorders (VDs). Heavy demands on the voice, especially for a long time or with loud back-ground noise, can lead to vocal abuse or misuse. The study aimed to measure the prevalence of perceived voice disorders among the teaching faculty at a female university, identify the risk fac-tors that affect their voice, and determine the effect of perceived voice disorders on their quality of life (QoL). The study sample consisted of female teaching faculty (N = 401). The ques-tionnaire included general sociodemographic data, general voice data, the vocal tract discomfort (VTD) scale, and the World Health Organization Quality of Life assessment (WHOQOL)-BREF. The results demonstrated that 44.1% of the participants had perceived voice disorders, and stress, reflux, and asthma had a significant relationship with self-perceived voice disorders. Furthermore, the data showed that self-perceived voice disorders negatively impacted the overall QoL of teaching faculty. Perceived voice disorders are affected by various factors, including health conditions, medications, and lifestyle choices. Although teaching characteristics and demo-graphic factors are believed to be the cause, in this study they did not significantly contribute to perceived voice disorders. Faculty members with perceived voice disorders have a poorer quality of life, highlighting the need for education on preventative vocal measures and awareness of voice care.

Assessment of Tracks of Resonance Frequencies of the Vocal Tract

A new method for estimating formant frequency tracks of the vocal tract for arbitrary speech segments is proposed. The method uses the ratio of two Fourier transforms of a speech signal with special exponential-type windows depending on some parameter. This ratio is used for specific points in time and is considered as a function of frequency and parameter. By analyzing, for several parameter values, the distribution of minimum points (in terms of frequency) for the phase of this ratio and/or a similar distribution of extreme points for its amplitude, it is possible to estimate formant frequencies from the peaks of these distributions. A mathematical study is presented that substantiates this approach. A series of numerical experiments were carried out on the processing of synthetic and real speech signals, which confirmed the performance capabilities of the proposed formant evaluation method. In particular, in experiments with synthesized vowels, it was found that the error in estimating their resonance frequencies is small and stable with respect to additive noise up to a signal-to-noise ratio of 5 dB. For real speech, the method makes it possible to calculate the formant frequency tracks for both sounds with vocal excitation and for voiceless fricatives, aspirated plosives, and whispered speech.

The Role of the Vocal Tract's Acousto-Mechanical Resonance on the Mechanism of Bubble Release From Tubes Used in SOVTE

The Role of the Vocal Tract's Acousto-Mechanical Resonance on the Mechanism of Bubble Release From Tubes Used in SOVTE

Super-Resolved Dynamic 3D Reconstruction of the Vocal Tract during Natural Speech.

MRI is the gold standard modality for speech imaging. However, it remains relatively slow, which complicates imaging of fast movements. Thus, an MRI of the vocal tract is often performed in 2D. While 3D MRI provides more information, the quality of such images is often insufficient. The goal of this study was to test the applicability of super-resolution algorithms for dynamic vocal tract MRI. In total, 25 sagittal slices of 8 mm with an in-plane resolution of 1.6 × 1.6 mm2 were acquired consecutively using a highly-undersampled radial 2D FLASH sequence. The volunteers were reading a text in French with two different protocols. The slices were aligned using the simultaneously recorded sound. The super-resolution strategy was used to reconstruct 1.6 × 1.6 × 1.6 mm3 isotropic volumes. The resulting images were less sharp than the native 2D images but demonstrated a higher signal-to-noise ratio. It was also shown that the super-resolution allows for eliminating inconsistencies leading to regular transitions between the slices. Additionally, it was demonstrated that using visual stimuli and shorter text fragments improves the inter-slice consistency and the super-resolved image sharpness. Therefore, with a correct speech task choice, the proposed method allows for the reconstruction of high-quality dynamic 3D volumes of the vocal tract during natural speech.

Effects of a Straw Phonation on Acoustic and Self-Reported Measures of Adolescent Female Singers: A Pilot Study

ABSTRACT Characteristics of adolescent female voice change include breathiness, inconsistent pitch, “cracks,” abrupt register transitions, vocal range changes, and decreased stamina. Researchers have found that semi-occluded vocal tract exercises (e.g. straw phonation) can assist with such difficulties with other varied populations, facilitating glottal closure, decreasing breathiness, and encouraging easier voicing. Therefore, the purpose of this investigation was to measure the effects of straw phonation (experimental) compared to “ah” vowel (control) warm-ups on acoustic and self-reported measures of seventh-grade female-identifying singers. We calculated each participant’s Acoustic Voice Quality Index (AVQI) prior to and after a 4–5-minute straw phonation (n = 6) or unoccluded “ah” vowel (n = 6) warm-up. Results indicated robust improvement in AVQI scores after both warm-ups, with a trend toward more acoustic improvement after straw phonation (5 improved, M = 0.48, compared to 4, M = 0.35). All participants self-reported that their respective voicing helped them to be more warmed up, but the effect was statistically much larger in the straw group (7.23 to 5.00, 10-point scale). Some participants self-reported that straw phonation was more effective than their typical warm-up. These results may indicate more robust benefits from straw phonation, which could facilitate increased motivation during a difficult transition.

Vocal tract shape variation contributes to individual vocal identity in African penguins.

Variation in formant frequencies has been shown to affect social interactions and sexual competition in a range of avian species. Yet, the anatomical bases of this variation are poorly understood. Here, we investigated the morphological correlates of formants production in the vocal apparatus of African penguins. We modelled the geometry of the supra-syringeal vocal tract of 20 specimens to generate a population of virtual vocal tracts with varying dimensions. We then estimated the acoustic response of these virtual vocal tracts and extracted the centre frequency of the first four predicted formants. We demonstrate that: (i) variation in length and cross-sectional area of vocal tracts strongly affects the formant pattern, (ii) the tracheal region determines most of this variation, and (iii) the skeletal size of penguins does not correlate with the trachea length and consequently has relatively little effect on formants. We conclude that in African penguins, while the variation in vocal tract geometry generates variation in resonant frequencies supporting the discrimination of conspecifics, such variation does not provide information on the emitter's body size. Overall, our findings advance our understanding of the role of formant frequencies in bird vocal communication.

Speech production real-time MRI at 0.55 T.

To demonstrate speech-production real-time MRI (RT-MRI) using a contemporary 0.55T system, and to identify opportunities for improved performance compared with conventional field strengths. Experiments were performed on healthy adult volunteers using a 0.55T MRI system with high-performance gradients and a custom 8-channel upper airway coil. Imaging was performed using spiral-based balanced SSFP and gradient-recalled echo (GRE) pulse sequences using a temporal finite-difference constrained reconstruction. Speech-production RT-MRI was performed with three spiral readout durations (8.90, 5.58, and 3.48 ms) to determine trade-offs with respect to articulator contrast, blurring, banding artifacts, and overall image quality. Both spiral GRE and bSSFP captured tongue boundary dynamics during rapid consonant-vowel syllables. Although bSSFP provided substantially higher SNR in all vocal tract articulators than GRE, it suffered from banding artifacts at TR > 10.9 ms. Spiral bSSFP with the shortest readout duration (3.48 ms, TR = 5.30 ms) had the best image quality, with a 1.54-times boost in SNR compared with an equivalent GRE sequence. Longer readout durations led to increased SNR efficiency and blurring in both bSSFP and GRE. High-performance 0.55T MRI systems can be used for speech-production RT-MRI. Spiral bSSFP can be used without suffering from banding artifacts in vocal tract articulators, provide better SNR efficiency, and have better image quality than what is typically achieved at 1.5 T or 3 T.

The influence of source-filter interaction on the voice source in a three-dimensional computational model of voice production.

The goal of this computational study is to quantify global effects of vocal tract constriction at various locations (false vocal folds, aryepiglottic folds, pharynx, oral cavity, and lips) on the voice source across a large range of vocal fold conditions. The results showed that while inclusion of a uniform vocal tract had notable effects on the voice source, further constricting the vocal tract only had small effects except for conditions of extreme constriction, at which constrictions at any location along the vocal tract decreased the mean and peak-to-peak amplitude of the glottal flow waveform. Although narrowing in the epilarynx increased the normalized maximum flow declination rate, vocal tract constriction in general slightly reduced the source strength and high-frequency harmonic production at the glottis, except for a limited set of vocal fold conditions (e.g., soft, long vocal folds subject to relatively high pressure). This suggests that simultaneous laryngeal and vocal tract adjustments are required to maximize source-filter interaction. While vocal tract adjustments are often assumed to improve voice production, our results indicate that such improvements are mainly due to changes in vocal tract acoustic response rather than improved voice production at the glottis.

The effect of vocal tract semi-occlusion on the voice source and implications for voice therapy

Semi-occluded vocal tract exercises are often used in voice therapy to improve voice production. It is generally assumed that by enhancing source-filter interaction, such vocal exercises improve vocal efficiency while minimizing vocal fold collision. The goal of this computational study is to quantify such effects of source–filter interaction on the voice source. Voice simulations were performed with vocal tract constriction at various locations (false vocal folds, aryepiglottic folds, pharynx, oral cavity, and lips). The results showed that effects of vocal tract constriction on the voice source were generally small except for conditions of extreme constriction, at which constrictions at any location along the vocal tract decreased the mean and peak-to-peak amplitude of the glottal flow waveform. In general, source-filter interaction that reduced vocal fold contact pressure also decreased sound pressure level, thus making it impractical when targeting a desired output vocal intensity. While source–filter interaction is often assumed to improve vocal efficiency and economy, our results indicate that such improvements are mainly due to improvement in the filter rather than the voice source at the glottis. It is possible that speakers make additional laryngeal adjustments during vocal exercises, which may also contribute to the therapeutic benefits of such exercises.