Laryngeal, Respiratory, and Acoustic Characteristics of Vocal Trillo With Simultaneous High-Speed Videoendoscopy, Inductive Plethysmography, and Acoustic Recordings.

OBJECTIVE: This study aimeed to examine the characteristics of formed and unformed trillo, an essential ornament found in 17th-century Italian vocal music, using simultaneous multimodality voice measurements. PARTICIPANT AND METHODS: A 28-year-old female with 12 years of classical voice training and 7 years of advanced training in historical performance produced formed trillo, unformed trillo, oscillating trill, vibrato, and straight tone on the vowel /i/. Simultaneous high-speed videoendoscopy, inductive plethysmography, and acoustic recordings were conducted to examine the laryngeal motion, respiratory kinematics, and output sound characteristics. RESULTS: The study findings reveal that trillo in this single participant is not only produced by the periodic adduction/abduction of the vocal fold but also with underlying differences in oscillatory mechanisms and increased glottal flow (use of percent vital capacity) controlled by increased activation of abdominal muscles and/or decreased activation (inspiratory braking) of the diaphragm relative to tidal breathing when compared with straight tone, vibrato, and oscillating trill. The formed trillo differs from the unformed trillo in the oscillatory mechanisms and glottal airflow utilization. CONCLUSIONS: The physiological mechanism responsible for trillo is more complex than simply adduction and abduction. Future studies with a greater number of participants are needed to evaluate the mechanisms responsible for the formation of and the auditory-perceptual differences between the formed versus unformed trillo.

Semi-occluded vocal tract exercises in healthy young adults: Articulatory, acoustic, and aerodynamic measurements during phonation at threshold.

Semi-occluded vocal tract exercises (SOVTEs) are increasingly popular as therapeutic exercises for patients with voice disorders. This popularity is reflected in the growing research literature, investigating the scientific principles underlying SOVTEs and their practical efficacy. This study examines several acoustic, articulatory, and aerodynamic variables before, during, and after short-duration (15 s) SOVTEs with a narrow tube in air. Participants were 20 healthy young adults, and all variables were measured at threshold phonation levels. Acoustic variables were measured with a microphone and a neck accelerometer, and include fundamental frequency, glottal open quotient, and vocal efficiency. Articulatory variables were measured with ultrasound, and include measures of the tongue tip, tongue dorsum, and posterior tongue height, and horizontal tongue length. Aerodynamic variables were measured with an intraoral pressure transducer and include subglottal, intraoral, and transglottal pressures. Lowering of the posterior tongue height and tongue dorsum height were observed with gender-specific small changes in the fundamental frequency, but there were no significant effects on the transglottal pressure or vocal efficiency. These findings suggest that the voices of healthy young adults already approach optimal performance, and the continued search for scientific evidence supporting SOVTEs should focus on populations with voice disorders.

Palatalization in coronal consonants of Polish: A three-/four-dimensional ultrasound study.

This paper presents the results of an articulatory study of palatalized consonants in Polish, a language with a typologically rare concentration of two phonemic series of posterior sibilants, one inherently palatalized, and the other contextually (allophonically) palatalized. For both phonemic and allophonic palatalization in Polish, it was found that the most stable correlates of palatalization are the advancement of the tongue root and a combined effect of raising and fronting of the tongue body. The advancement of the tongue root can be interpreted as the driving force in palatalization, while the effect of tongue body fronting and raising can be seen as secondary, resulting from the movement of the tongue root and the characteristic of the tongue as a muscular hydrostat.

Automatic tongue surface extraction from three-dimensional ultrasound vocal tract images.

Three-dimensional (3D/4D) ultrasound (US) imaging of the tongue has emerged as a useful instrument for articulatory studies. However, extracting quantitative measurements of the shape of the tongue surface remains challenging and time-consuming. In response to these challenges, this paper documents and evaluates the first automated method for extracting tongue surfaces from 3D/4D US data. The method draws on established methods in computer vision, and combines image phase symmetry measurements, eigen-analysis of the image Hessian matrix, and a fast marching method for surface evolution towards the automatic detection of the sheet-like surface of the tongue amidst noisy US data. The method was tested on US recordings from eight speakers and the resulting automatically extracted tongue surfaces were generally found to lie within 1 to 2 mm from their corresponding manually delineated surfaces in terms of mean-sum-of-distances error. Further experiments demonstrate that the accuracy of 2D midsagittal tongue contour extraction is also improved using 3D data and methods. This is likely because the additional information afforded by 3D US compared to 2D US images strongly constrains the possible location of the midsagittal contour. Thus, the proposed method seems appropriate for immediate practical use in the analysis of 3D/4D US recordings of the tongue.

Articulatory and acoustic characteristics of the Korean and English word-final laterals produced by Korean female learners of American English.

English [É«] exhibits retracted tongue dorsum and low F2 frequencies compared to Korean [l], but is frequently asserted to be perceptually similar to Korean [l] and therefore difficult for Korean learners to acquire due to articulatory transfer. This study examines the articulatory and acoustic characteristics of Korean and English word-final laterals produced by Korean learners. Korean learners' productions of English [É«] were systematically different from Korean [l], with retracted tongue dorsum and low F2 similar to L1 English [É«]. The findings suggest Korean learners form a distinct phonetic category for English [É«] rather than modifying an existing Korean category.

Phonetics of Polish "soft"-"hard" vowel allophony.

This paper reports on the results of a three-dimensional ultrasound study of Polish vowels in consonant-vowel sequences. It was found that allophonic variation in vowels in the context of "soft" consonants is consistently implemented phonetically by means of tongue root advancement, which effectively expands the pharyngeal cavity and reduces the volume of the oral cavity. The tongue root is also consistently advanced in the soft consonants that trigger vowel allophony and retracted (or neutral) in the "hard" sounds, which do not trigger allophony, suggesting that tongue root advancement is part of the phonological representation of the "softness" (or palatalization) contrast. In parallel to this allophony, the same tongue root mechanism was found to underlie the phonotactic distribution of the phonemic vowels /i/ and /ɨ/, yielding an entirely symmetric system with consonant-vowel sequences always obligatorily compatible in terms of the position of the tongue root.

Vocal tract shape and acoustic adjustments of children during phonation into narrow flow-resistant tubes.

The goal of the study is to quantify the salient vocal tract acoustic, subglottal acoustic, and vocal tract physiological characteristics during phonation into a narrow flow-resistant tube with 2.53 mm inner diameter and 124 mm length in typically developing vocally healthy children using simultaneous microphone, accelerometer, and 3D/4D ultrasound recordings. Acoustic measurements included fundamental frequency (fo), first formant frequency (F1), second formant frequency (F2), first subglottal resonance (FSg1), and peak-to-peak amplitude ratio (Pvt:Psg). Physiological measurements included posterior tongue height (D1), tongue dorsum height (D2), tongue tip height (D3), tongue length (D4), oral cavity width (D5), hyoid elevation (D6), pharynx width (D7). All measurements were made on eight boys and ten girls (6-9 years) during sustained /o:/ production at typical pitch and loudness, with and without flow-resistant tube. Phonation with the flow-resistant tube resulted in a significant decrease in F1, F2, and Pvt:Psg and a significant increase in D2, D3, and FSg1. A statistically significant gender effect was observed for D1, with D1 higher in boys. These findings agree well with reported findings from adults, suggesting common acoustic and articulatory mechanisms for narrow flow-resistant tube phonation. Theoretical implications of the findings are discussed.

Articulatory-acoustic relations in the production of alveolar and palatal lateral sounds in Brazilian Portuguese.

Lateral approximant speech sounds are notoriously difficult to measure and describe due to their complex articulation and acoustics. This has prevented researchers from reaching a unifying description of the articulatory and acoustic characteristics of laterals. This paper examines articulatory and acoustic properties of Brazilian Portuguese alveolar and palatal lateral approximants (/l/ and /ʎ/) produced by six native speakers. The methodology for obtaining vocal tract area functions was based on three-dimensional/four-dimensional (3D/4D) ultrasound recordings and 3D digitized palatal impressions with simultaneously recorded audio signals. Area functions were used to calculate transfer function spectra, and predicted formant and anti-resonance frequencies were compared with the acoustic recordings. Mean absolute error in formant frequency prediction was 4% with a Pearson correlation of r = 0.987. Findings suggest anti-resonances from the interdental channels are less important than a prominent anti-resonance from the supralingual cavity but can become important in asymmetrical articulations. The use of 3D/4D ultrasound to study articulatory-acoustic relations is promising, but significant limitations remain and future work is needed to make better use of 3D/4D ultrasound data, e.g., by combining it with magnetic resonance imaging.

Subglottal resonances of American English speaking children.

This paper presents an investigation of children's subglottal resonances (SGRs), the natural frequencies of the tracheo-bronchial acoustic system. A total of 43 children (31 male, 12 female) aged between 6 and 18 yr were recorded. Both microphone signals of various consonant-vowel-consonant words and subglottal accelerometer signals of the sustained vowel /ɑ/ were recorded for each of the children, along with age and standing height. The first three SGRs of each child were measured from the sustained vowel subglottal accelerometer signals. A model relating SGRs to standing height was developed based on the quarter-wavelength resonator model, previously developed for adult SGRs and heights. Based on difficulties in predicting the higher SGR values for the younger children, the model of the third SGR was refined to account for frequency-dependent acoustic lengths of the tracheo-bronchial system. This updated model more accurately estimates both adult and child SGRs based on their heights. These results indicate the importance of considering frequency-dependent acoustic lengths of the subglottal system.

The relation between tongue shape and pitch in clarinet playing using ultrasound measurements.

Tongue shapes during clarinet performances of chromatic scale, portamento and pitch bending exercises were imaged using an ultrasound machine while audio and video were recorded synchronously. Analysis of the data from four participants revealed that tongue position varies non-monotically with note frequency in the lowest register (up to ≈ 440 Hz) and then descends monotonically as note frequencies rise through the upper registers. The descent of the tongue results in an expansion of the vocal tract's posterior oral cavity, resulting in a vocal tract input impedance maximum tuned to high frequency. Portamento and pitch bending were found to involve a raising of the tongue and concomitant contraction of the posterior oral cavity. The degree of contraction was similar in both portamento and pitch bending, suggesting a common acoustic mechanism.

Tracheo-bronchial soft tissue and cartilage resonances in the subglottal acoustic input impedance.

This paper offers a re-evaluation of the mechanical properties of the tracheo-bronchial soft tissues and cartilage and uses a model to examine their effects on the subglottal acoustic input impedance. It is shown that the values for soft tissue elastance and cartilage viscosity typically used in models of subglottal acoustics during phonation are not accurate, and corrected values are proposed. The calculated subglottal acoustic input impedance using these corrected values reveals clusters of weak resonances due to soft tissues (SgT) and cartilage (SgC) lining the walls of the trachea and large bronchi, which can be observed empirically in subglottal acoustic spectra. The model predicts that individuals may exhibit SgT and SgC resonances to variable degrees, depending on a number of factors including tissue mechanical properties and the dimensions of the trachea and large bronchi. Potential implications for voice production and large pulmonary airway tissue diseases are also discussed.

The effect of exposure to a single vowel on talker normalization for vowels.

The current work investigated the role of single vowels in talker normalization. Following initial training to identify six talkers from the isolated vowel /i/, participants were asked to identify vowels in three different conditions. In the blocked-talker conditions, the vowels were blocked by talker. In the mixed-talker conditions, vowels from all six talkers were presented in random order. The precursor mixed-talker conditions were identical to the mixed-talker conditions except that participants were provided with either a sample vowel or just the written name of a talker before target-vowel presentation. In experiment 1, the precursor vowel was always spoken by the same talker as the target vowel. Identification accuracy did not differ significantly for the blocked and precursor mixed-talker conditions and both were better than the pure mixed-talker condition. In experiment 2, half of the trials had a precursor spoken by the same talker as the target and half had a different talker. For the same-talker precursor condition, the results replicated those in experiment 1. In the different-talker precursor, no benefit was observed relative to the pure-mixed condition. In experiment 3, only the written name was presented as a precursor and no benefits were observed relative to the pure-mixed condition.

Subglottal resonances of adult male and female native speakers of American English.

This paper presents a large-scale study of subglottal resonances (SGRs) (the resonant frequencies of the tracheo-bronchial tree) and their relations to various acoustical and physiological characteristics of speakers. The paper presents data from a corpus of simultaneous microphone and accelerometer recordings of consonant-vowel-consonant (CVC) words embedded in a carrier phrase spoken by 25 male and 25 female native speakers of American English ranging in age from 18 to 24 yr. The corpus contains 17,500 utterances of 14 American English monophthongs, diphthongs, and the rhotic approximant [[inverted r]] in various CVC contexts. Only monophthongs are analyzed in this paper. Speaker height and age were also recorded. Findings include (1) normative data on the frequency distribution of SGRs for young adults, (2) the dependence of SGRs on height, (3) the lack of a correlation between SGRs and formants or the fundamental frequency, (4) a poor correlation of the first SGR with the second and third SGRs but a strong correlation between the second and third SGRs, and (5) a significant effect of vowel category on SGR frequencies, although this effect is smaller than the measurement standard deviations and therefore negligible for practical purposes.

Resonances and wave propagation velocity in the subglottal airways.

Previous studies of subglottal resonances have reported findings based on relatively few subjects, and the relations between these resonances, subglottal anatomy, and models of subglottal acoustics are not well understood. In this study, accelerometer signals of subglottal acoustics recorded during sustained [a:] vowels of 50 adult native speakers (25 males, 25 females) of American English were analyzed. The study confirms that a simple uniform tube model of subglottal airways, closed at the glottis and open at the inferior end, is appropriate for describing subglottal resonances. The main findings of the study are (1) whereas the walls may be considered rigid in the frequency range of Sg2 and Sg3, they are yielding and resonant in the frequency range of Sg1, with a resulting ~4/3 increase in wave propagation velocity and, consequently, in the frequency of Sg1; (2) the "acoustic length" of the equivalent uniform tube varies between 18 and 23.5 cm, and is approximately equal to the height of the speaker divided by an empirically determined scaling factor; (3) trachea length can also be predicted by dividing height by another empirically determined scaling factor; and (4) differences between the subglottal resonances of males and females can be accounted for by height-related differences.

Automatic estimation of the first subglottal resonance.

This letter focuses on the automatic estimation of the first subglottal resonance (Sg1). A database comprising speech and subglottal data of native American English speakers and bilingual Spanish/English speakers was used for the analysis. Data from 11 speakers (five males and six females) were used to derive an empirical relation among the first formant frequency, fundamental frequency, and Sg1. Using the derived relation, Sg1 was automatically estimated from voiced sounds in English and Spanish sentences spoken by 22 different speakers (11 males and 11 females). The error in estimating Sg1 was less than 50 Hz, on average.

Automatic detection of the second subglottal resonance and its application to speaker normalization.

Speaker normalization typically focuses on inter-speaker variabilities of the supraglottal (vocal tract) resonances, which constitute a major cause of spectral mismatch. Recent studies have shown that the subglottal airways also affect spectral properties of speech sounds, and promising results were reported using the subglottal resonances for speaker normalization. This paper proposes a reliable algorithm to automatically estimate the second subglottal resonance (Sg2) from speech signals. The algorithm is calibrated on children's speech data with simultaneous accelerometer recordings from which Sg2 frequencies can be directly measured. A cross-language study with bilingual Spanish-English children is performed to investigate whether Sg2 frequencies are independent of speech content and language. The study verifies that Sg2 is approximately constant for a given speaker and thus can be a good candidate for limited data speaker normalization and cross-language adaptation. A speaker normalization method using Sg2 is then presented. This method is computationally more efficient than maximum-likelihood based vocal tract length normalization (VTLN), with performance better than VTLN for limited adaptation data and cross-language adaptation. Experimental results confirm that this method performs well in a variety of testing conditions and tasks.

A role for the second subglottal resonance in lexical access.

Acoustic coupling between the vocal tract and the lower (subglottal) airway results in the introduction of pole-zero pairs corresponding to resonances of the uncoupled lower airway. If the second formant (F2) passes through the second subglottal resonance a discontinuity in amplitude occurs. This work explores the hypothesis that this F2 discontinuity affects how listeners perceive the distinctive feature [back] in transitions from a front vowel (high F2) to a labial stop (low F2). Two versions of the utterances "apter" and "up there" were synthesized with an F2 discontinuity at different locations in the initial VC transition. Subjects heard portions of the utterances with and without the discontinuity, and were asked to identify whether the utterances were real words or not. Results show that the frequency of the F2 discontinuity in an utterance influences the perception of backness in the vowel. Discontinuities of this sort are proposed to play a role in shaping vowel inventories in the world's languages [K. N. Stevens, J. Phonetics 17, 3-46 (1989)]. The results support a model of lexical access in which articulatory-acoustic discontinuities subserve phonological feature identification.