Glottal Adduction Research Articles

Emotional expressivity in singing. Assessing physiological and acoustic indicators of two opera singers' voice characteristics.

In an earlier study, we analyzed how audio signals obtained from three professional opera singers varied when they sang one octave wide eight-tone scales in ten different emotional colors. The results showed systematic variations in voice source and long-term-average spectrum (LTAS) parameters associated with major emotion "families". For two of the singers, subglottal pressure (PSub) also was recorded, thus allowing analysis of an additional main physiological voice control parameter, glottal resistance (defined as the ratio between PSub and glottal flow), and related to glottal adduction. In the present study, we analyze voice source and LTAS parameters derived from the audio signal and their correlation with Psub and glottal resistance. The measured parameters showed a systematic relationship with the four emotion families observed in our previous study. They also varied systematically with values of the ten emotions along the valence, power, and arousal dimensions; valence showed a significant correlation with the ratio between acoustic voice source energy and subglottal pressure, while Power varied significantly with sound level and two measures related to the spectral dominance of the lowest spectrum partial. the fundamental.

Female adolescent singing voice characteristics: an exploratory study using LTAS and inverse filtering

Background and Aim: To date, little research is available that objectively quantifies female adolescent singing-voice characteristics in light of the physiological and functional developments that occur from puberty to adulthood. This exploratory study sought to augment the pool of data available that offers objective voice analysis of female singers in late adolescence. Methods: Using long-term average spectra (LTAS) and inverse filtering techniques, dynamic range and voice-source characteristics were determined in a cohort of vocally healthy cis-gender female adolescent singers (17 to 19 years) from high-school choirs in Aotearoa New Zealand. Non-parametric statistics were used to determine associations and significant differences. Results: Wide intersubject variation was seen between dynamic range, spectral measures of harmonic organisation (formant cluster prominence, FCP), noise components in the spectrum (high-frequency energy ratio, HFER), and the normalised amplitude quotient (NAQ) suggesting great variability in ability to control phonatory mechanisms such as subglottal pressure (Psub), glottal configuration and adduction, and vocal tract shaping. A strong association between the HFER and NAQ suggest that these non-invasive measures may offer complimentary insights into vocal function, specifically with regard to glottal adduction and turbulent noise in the voice signal. Conclusion: Knowledge of the range of variation within healthy adolescent singers is necessary for the development of effective and inclusive pedagogical practices, and for vocal-health professionals working with singers of this age. LTAS and inverse filtering are useful non-invasive tools for determining such characteristics.

Augmented visual-feedback of airflow: Immediate effects on voice-source characteristics of students of singing

Glottal adduction is a crucial aspect in voice education and vocal performance: it has major effects on phonatory airflow and, consequently, on voice timbre. As the voice is a non-visible musical instrument, controlling it could be facilitated by providing real-time visual feedback of phonatory airflow. Here, we test the usefulness of a flow ball (FB) training device, visualizing, in terms of the height of a polystyrene ball placed in a plastic basket, phonatory airflow during phonation. Audio and electroglottographic recordings of five postgraduate, classically trained singer students were made under three subsequent conditions: before, during, and after phonating into the FB. The calibrated audio signal was inverse-filtered, using an electroglottograph signal to guide the manual tuning of the inverse filters. Mean phonatory airflow, peak-to-peak pulse amplitude, and normalized amplitude quotient were extracted from the resulting flow glottograms. After the FB condition, increases of mean flow and peak-to-peak pulse amplitude were observed in four singers. In addition, the singers’ mean normalized amplitude quotient increased significantly. The findings, although exploratory, suggest that reduction of glottal adduction can be observed immediately after FB phonation.

Objective Measures of Two Musical Interpretations of an Excerpt From Berlioz's “La mort d'Ophélie”

This study aimed to determine objective production differences relative to two emotional interpretations in performing an excerpt from a classical art song. The null hypothesis was proposed. The first author recorded an excerpt from an art song. The excerpt was sung with two contrasting musical interpretations: an "empathetic legato" approach, and a "sarcastic" approach characterized by emphatic attacks. Microphone, airflow, and electroglottography signals were digitized. The vowels were analyzed in terms of intensity, long term average spectra, fundamental frequency (fo), airflow vibrato rate and extent, vowel onset slope, intensity comparison of harmonic frequencies, and glottal measures based on electroglottograph waveforms. Four consonant tokens were analyzed relative to airflow, voice onset time, and production duration. The emphatic performance had faster vowel onset, increased glottal adduction, increased intensity of harmonics in 2-3 kHz, increased intensity in the fourth and fifth formants, inferred subglottal pressure increase, increased airflow for /f/, and greater aspiration airflow for /p, t/. Vibrato extents for intensity, fo, and airflow were wider in the emphatic approach. Findings revealed larger EGGW25 and peak-to-peak amplitude values of the electroglottography waveform, suggesting greater vocal fold contact area and longer glottal closure for the emphatic approach. Long-term average spectrum analyses of the entire production displayed minor variation across all formant frequencies, suggesting an insignificant change in vocal tract shaping between the two approaches. This single-case objective study emphasizes the reality of physiological, aerodynamic, and acoustic production differences in the interpretive and pedagogical aspects of art song performance.

Nasal Resistance (NR) Technique: A Novel Approach to Improve Glottal Adduction

Several techniques have been practiced in the field of voice therapy to balance glottal pressures and improve glottal adduction. As such, Semioccluded Vocal Tract Exercises using narrow diameter straws have shown promise as a technique to increase glottal contact as reflected by Closed Quotients (CQ) measured from electroglottograph (EGG). This study explored the effect of nasal resistance (NR) technique, a manually induced NR approach, on glottal adduction in phononormal subjects as a possible new therapeutic technique to assist in glottal closure. Thirty-four vocally healthy adult females qualified for this study. All subjects were reportedly and perceptually normal. Subjects were instructed to perform tasks including (a) steady modal phonation, (b) straw phonation, (c) humming, and (d) NR technique in a random order. EGG measures included calculation of the CQ and jitter during the mid-section of each stimuli for a minimum of 10 EGG cycles. One-way repeated measures ANOVAs and Bonferroni post-hoc comparisons were calculated to determine differences between each phonatory task for the outcome measures of CQ and jitter. Analyses revealed that the mean CQ was significantly different in all the tasks performed with humming (33.99%) at the lowest and NR technique at highest (43.88%). Though the CQ of straw phonation (40.53%) was higher than modal steady phonation (36.65%), jitter was found to be significantly lower for NR technique (0.23%). Jitter during straw phonation (0.43%) did not differ significantly from modal phonation (0.44%). These results provide preliminary evidence that NR technique can increase CQ with lower levels of jitter compared to straw phonation using a narrow diameter of 2 mm. Future studies should expand enrollment to men, larger age ranges, and patients with hypofunctional symptoms (eg, Parkinson disease) to evaluate the potential benefits of NR as a therapeutic technique.

Voice Characteristics of Young Girl Role in Kunqu Opera

Three electroglottographic parameters, fundamental frequency, contact quotient, and speed quotient were analyzed for two singers of Young girl role in Kunqu Opera. Each singer performed three conditions, singing, stage speech, and reading lyrics. The phonation types adopted in different conditions were explored based on electroglottographic parameters. Fundamental frequency, contact quotient, and speed quotient showed different distributions among conditions. Five phonation types were used in singing and stage speech, which include (1) breathy voice, (2) modal voice with low degree of posterior glottal adduction, (3) modal voice, (4) falsetto, and (5) falsetto with high degree of posterior glottal adduction. The phonation strategies partly showed differences between singers. Different phonation type collocations were employed in singing and stage speech. The relationship between phonation types and pitch was complex. The phonation types actually used were different from and more complex than those in traditional Kunqu Opera singing theory.

Aerodynamic Characteristics of Growl Voice and Reinforced Falsetto in Metal Singing

The present study aimed to assess the aerodynamic characteristics of vocally healthy metal singers when producing growl voice or reinforced falsetto. Fifty-four participants (metal singers) were initially enrolled in this study, with 23 meeting the inclusion criteria. Sixteen participants performed growl voice and seven performed reinforced falsetto as a voice resource during metal singing. All participants were asked to undergo rigid laryngeal videostroboscopy to confirm the absence of laryngeal pathology. Then, subjects were aerodynamically assessed while performing growl voice or reinforced falsetto. Higher glottal airflow rate, sound pressure level, and subglottic pressure (Psub) for growl voice samples compared to vowel production without growl voice (keeping the same fundamental frequency [F0]) were found. Higher Psub, sound pressure level, and glottal resistance for high-pitched reinforced falsetto compared to naïve falsetto (keeping the same F0) were found. No differences for F0 were found for neither growl voice nor reinforced falsetto. It seems that growl voice is produced by decreasing vocal folds adduction and increasing Psub, which in turn, promotes an increased airflow rate. Reinforced falsetto is characterized by an increased vocal fold adduction and an increased Psub. A proper resonance strategy in reinforced falsetto and a decreased glottal adduction in growl voice might probably be the factors that contribute to prevent voice problems in singers who use these vocal resources, classically labeled as vocal abuse.

Empirical eigenfunctions as a function of glottal adduction in excised hemilarynx experiments

For three excised human male hemilarynxes, vocal fleshpoints and empirical eigenfunctions were computed along the vocal fold surface. For two larynges, an increase in adduction resulted in an increase in lateral and vertical oscillation amplitudes and an improved energy transfer from the airflow to the vocal fold tissues. In contrast, the third larynx exhibited a decrease in oscillation amplitudes. By evaluating the empirical eigenfunctions, this decrease in oscillation amplitudes was associated with an unbalanced oscillation pattern with predominantly lateral amplitudes. These results suggest that adduction facilitates the phonatory process by increasing vibrational amplitudes. However, this relationship holds only when a balanced ratio between the vertical and lateral displacements is maintained. Indeed, it appears that a balanced vertical-lateral oscillation pattern may be more beneficial to phonation than strong periodicity with predominantly lateral vibrations.

Quantitative Evaluation of the In Vivo Vocal Fold Medial Surface Shape

Glottal insufficiency is a common clinical problem in otolaryngology and medialization laryngoplasty (ML) procedures remain the primary treatment modality. Although the goal of ML is to restore physiologic glottal posture and achieve optimal phonation, this posture has not been directly measured. In this study, we assessed glottal medial surface contour changes with selective activation of the intrinsic laryngeal muscles (ILMs). Basic science study using an in vivo canine hemilarynx model. In an in vivo canine hemilarynx, India ink was used to mark fleshpoints in a grid-like fashion along the medial surface of the vocal fold and ILMs were activated in a graded manner. A right-angled prism provided two views of the medial surface, which were recorded using a high-speed camera and used to reconstruct the 3D posture deformations of the medial surface. Thyroarytenoid (TA) muscle activation results in initial inferomedial bulging and increased glottal channel thickness and then glottal adduction with a final rectangular glottal channel shape. Lateral cricoarytenoid (LCA) activation closes the posterior glottis but final posture remains slightly convergent. Together, TA + LCA forms a rectangular glottis with an increased glottal vertical thickness. Posterior cricoarytenoid activation results in abduction and a slightly divergent glottis, whereas cricothyroid activation elongates the glottis and reduces the glottal channel vertical thickness. A quantitative analysis of in vivo canine vocal fold medial surface upon activation of selective ILMs is provided. This may guide our therapeutic efforts during medialization laryngoplasty, as well as computational modeling of laryngeal physiology.

Relationship Between Acoustic Voice Onset and Offset and Selected Instances of Oscillatory Onset and Offset in Young Healthy Men and Women

This study aimed to investigate the relationship between (1) onset of the acoustic signal (X1a) and prephonatory phases associated with oscillatory onset and (2) offset of the acoustic signal (X2a) with the postphonatory events associated with oscillatory offset across vocally healthy adults. High-speed videoendoscopy was captured simultaneously with the acoustic signal during repeated production of /hi.hi.hi/ at typical pitch and loudness from 56 vocally healthy adults (aged 20-42 years; 21 men, 35 women). The relationships between the acoustic sound pressure signal and oscillatory onset and offset events from the glottal area waveforms (GAWs) were statistically investigated using a multivariate linear regression analysis. The X1a is a significant predictor of the onset of first oscillatory motion (X1g) and onset of sustained oscillations (X2g). X1a as well as gender are significant predictors of the first medial contact of the vocal folds (X1.5g). The X2a is a significant predictor of the first instance of oscillatory offset (X3g), first instance of incomplete glottal closure (X3.5g), and complete cessation of (vocal fold) oscillatory motion (X4g). The acoustic signal onset is closely related to the X1.5g, but the latency between these events is longer for women compared to men. The X2a occurs immediately after incomplete glottal adduction. The emerging normative group latencies between the onset and offset of the acoustic and the GAW from this study appear promising for future investigations.

Phonatory Strategies of Male Vocalists in Singing Diatonic Scales With Various Dynamic Shapings

This work aimed to investigate glottal adduction in the case of the singing of diatonic D major ascending scales with different dynamic shapings on vowel [a:] by 10 classically trained male singers. The parameters obtained by inverse filtering-closed quotient (CQ), normalized amplitude quotient (NAQ), and the level difference between the first two partials of the glottal flow waveform spectrum (H1-H2)-all indicated statistically significant systematic changes when singers sang (1) with habitual dynamics without intentional dynamic changes; (2) with sempre crescendo from piano to forte; and (3) with sempre diminuendo from forte to piano. Adduction on average was lower if the tone with the same pitch was sung piano compared with when it was sung forte. The piano tones with the limit of one and the same dynamic task were sung with lower adduction on average compared with one octave higher or lower tones sung forte, although here the agreement between different parameters was poorer and the individual variability was greater. There was only a moderate negative correlation between CQ and NAQ (r = -0.41) but a strong negative correlation between CQ and H1-H2 (r = -0.8). CQ showed a moderate positive correlation with sound level but no significant correlation with pitch. NAQ showed a strong and significant positive correlation with pitch but not with sound level (except when it was calculated only at constant pitch). Some of the most experienced singers used quite high glottal adduction levels, questioning the concept of whether flow phonation is always the favorite classical style.

Soul and Musical Theater: A Comparison of Two Vocal Styles

The phonatory and resonatory characteristics of nonclassical styles of singing have been rarely analyzed in voice research. Six professional singers volunteered to sing excerpts from two songs pertaining to the musical theater and to the soul styles of singing. Voice source parameters and formant frequencies were analyzed by inverse filtering tones, sung at the same fundamental frequencies in both excerpts. As compared with musical theater, the soul style was characterized by significantly higher subglottal pressure and maximum flow declination rate. Yet sound pressure level was lower, suggesting higher glottal resistance. The differences would be the effects of firmer glottal adduction and a greater frequency separation between the first formant and its closest spectrum partial in soul than in musical theater.

Do Different Semi-Occluded Voice Exercises Affect Vocal Fold Adduction Differently in Subjects Diagnosed with Hyperfunctional Dysphonia?

Objective: To observe the possible differential effects of 8 different semi-occluded vocal tract exercises on glottal contact quotient (CQ) as a measure of vocal fold impact stress. Patients and Methods: Eighty participants were divided into two groups: an experimental group with hyperfunctional dysphonia and a control group of vocally healthy subjects. The participants were recorded before, during and after the exercises. Electroglottographic samples were analyzed to obtain CQ. Results: For the experimental group, all exercises, except lip trills and tongue trills, had an overall significant effect when conditions before, during and after the exercises were compared. The CQ presented differently across the 8 semi-occluded postures during exercise for both groups. For the experimental group, most exercises increased the CQ during practice. Only lip and tongue trills demonstrated lower CQ during exercise. Conclusions: Different semi-occluded exercises differentially affect vocal fold adduction. Lip and tongue trills produced the lowest CQ. Therefore, they may be recommended for decreasing glottal adduction. A straw submerged 10 cm below the water surface presented the greatest CQ. A shallower depth led to a lower CQ, while deeper submersion produced a higher CQ.

Glottal Adduction and Subglottal Pressure in Singing

Previous research suggests that independent variation of vocal loudness and glottal configuration (type and degree of vocal fold adduction) does not occur in untrained speech production. This study investigated whether these factors can be varied independently in trained singing and how subglottal pressure is related to average glottal airflow, voice source properties, and sound level under these conditions. A classically trained baritone produced sustained phonations on the endoscopic vowel [i:] at pitch D4 (approximately 294 Hz), exclusively varying either (a) vocal register; (b) phonation type (from "breathy" to "pressed" via cartilaginous adduction); or (c) vocal loudness, while keeping the others constant. Phonation was documented by simultaneous recording of videokymographic, electroglottographic, airflow and voice source data, and by percutaneous measurement of relative subglottal pressure. Register shifts were clearly marked in the electroglottographic wavegram display. Compared with chest register, falsetto was produced with greater pulse amplitude of the glottal flow, H1-H2, mean airflow, and with lower maximum flow declination rate (MFDR), subglottal pressure, and sound pressure. Shifts of phonation type (breathy/flow/neutral/pressed) induced comparable systematic changes. Increase of vocal loudness resulted in increased subglottal pressure, average flow, sound pressure, MFDR, glottal flow pulse amplitude, and H1-H2. When changing either vocal register or phonation type, subglottal pressure and mean airflow showed an inverse relationship, that is, variation of glottal flow resistance. The direct relation between subglottal pressure and airflow when varying only vocal loudness demonstrated independent control of vocal loudness and glottal configuration. Achieving such independent control of phonatory control parameters would be an important target in vocal pedagogy and in voice therapy.

Respiratory and Acoustical Differences Between Belt and Neutral Style of Singing

Belt is a style of singing commonly used in nonclassical genres. Its respiratory, phonatory, and resonatory characteristics are unclear. Basic research. Six female singers, professionally performing in the belt styles since many years, sang an excerpt of a song in belt and nonbelt/neutral style, two times with the lyrics and two times replacing the lyrics with /pae/ syllables. On separate channels, recordings were made of audio, oral pressure, and rib cage and abdominal wall movements, as picked up by respiratory inductive plethysmography. Lung volume and breathing patterns during inhalation and phonation were normalized with respect to duration and averaged. Voice source was analyzed in terms of flow glottograms derived from the audio signal by inverse filtering. Belt was produced with higher pressures and yielded higher sound levels, but no consistent breathing pattern was observed, neither for the belt, nor for the neutral style. Voice source differences suggested that belt was produced with firmer glottal adduction than neutral. Also, in four of the singers, the first formant was closer to a spectrum harmonic in belt than in neutral. Belt style of singing is not associated with a characteristic breathing behavior but is produced with higher subglottal pressures, higher sound levels, and firmer glottal adduction than a neutral style of singing.

Electrophysiological properties of laryngeal motoneurones in rats submitted to chronic intermittent hypoxia.

The respiratory control of the glottis by laryngeal motoneurones is characterized by inspiratory abduction and post-inspiratory adduction causing decreases and increases in upper airway resistance, respectively. Chronic intermittent hypoxia (CIH), an important component of obstructive sleep apnoea, exaggerated glottal abduction (before inspiration), associated with active expiration and decreased glottal adduction during post-inspiration. CIH increased the inspiratory and decreased the post-inspiratory laryngeal motoneurone activities, which is not associated to changes in their intrinsic electrophysiological properties. We conclude that the changes in the respiratory network after CIH seem to be an adaptive process required for an appropriated pulmonary ventilation and control of upper airway resistance under intermittent episodes of hypoxia. To keep an appropriate airflow to and from the lungs under physiological conditions a precise neural co-ordination of the upper airway resistance by laryngeal motoneurones in the nucleus ambiguus is essential. Chronic intermittent hypoxia (CIH), an important component of obstructive sleep apnoea, may alter these fine mechanisms. Here, using nerve and whole cell patch clamp recordings in in situ preparations of rats we investigated the effects of CIH on the respiratory control of the upper airway resistance, on the electrophysiological properties of laryngeal motoneurones in the nucleus ambiguus, and the role of carotid body (CB) afferents to the brainstem on the underlying mechanisms of these effects. CIH rats exhibited longer pre-inspiratory and lower post-inspiratory superior laryngeal nerve activities than control rats. These changes produced exaggerated glottal abduction (before inspiration) and decreased glottal adduction during post-inspiration, indicating a reduction of upper airway resistance during these respiratory phases after CIH. CB denervation abolished these changes produced by CIH. Regarding choline acetyltransferase positive-laryngeal motoneurones, CIH increased the firing frequency of inspiratory and decreased the firing frequency of post-inspiratory laryngeal motoneurones, without changes in their intrinsic electrophysiological properties. These data show that the effects of CIH on the upper airway resistance and laryngeal motoneurones activities are driven by the integrity of CB, which afferents induce changes in the central respiratory generators in the brainstem. These neural changes in the respiratory network seem to be an adaptive process required for an appropriated pulmonary ventilation and control of upper airway resistance under intermittent episodes of hypoxia.

Laryngoscopic and Spectral Analysis of Laryngeal and Pharyngeal Configuration in Non-Classical Singing Styles

The present study aimed to assess three different singing styles (pop, rock, and jazz) with laryngoscopic, acoustic, and perceptual analysis in healthy singers at different loudness levels. Special emphasis was given to the degree of anterior-posterior (A-P) laryngeal compression, medial laryngeal compression, vertical laryngeal position (VLP), and pharyngeal compression. Prospective study. Twelve female trained singers with at least 5years of voice training and absence of any voice pathology were included. Flexible and rigid laryngeal endoscopic examinations were performed. Voice recording was also carried out. Four blinded judges were asked to assess laryngoscopic and auditory perceptual variables using a visual analog scale. All laryngoscopic parameters showed significant differences for all singing styles. Rock showed the greatest degree for all of them. Overall A-P laryngeal compression scores demonstrated significantly higher values than overall medial compression and VLP. High loudness level produced the highest degree of A-P compression, medial compression, pharyngeal compression, and the lowest VLP for all singing styles. Additionally, rock demonstrated the highest values for alpha ratio (less steep spectral slope), L1-L0 ratio (more glottal adduction), and Leq (more vocal intensity). Statistically significant differences between the three loudness levels were also found for these acoustic parameters. Rock singing seems to be the style with the highest degree of both laryngeal and pharyngeal activity in healthy singers. Although, supraglottic activity during singing could be labeled as hyperfunctional vocal behavior, it may not necessarily be harmful, but a strategy to avoid vocal fold damage.

Formant and Voice Source Properties in Two Male Kunqu Opera Roles: A Pilot Study

Objective: This investigation analyzes flow glottogram and electroglottogram (EGG) parameters as well as the relationship between formant frequencies and partials in two male Kunqu Opera roles, Colorful face (CF) and Old man (OM). Participants and Methods: Four male professional Kunqu Opera singers volunteered as participants, 2 singers for each role. Using inverse filtering of the audio signal flow glottogram parameters and formant frequencies were measured in each note of scales. Two EGG parameters, contact quotient (CoQ) and speed quotient, were measured. Results: Formant tuning was observed only in 1 of the OM singers and appeared in a pitch range lower than the passaggio range of Western male opera singers. Both the CF and the OM role singers showed high CoQ values and low values of the normalized amplitude quotient in singing. For 3 of the 4 singers CoQ and the level difference between the first and second partials showed a positive and a negative correlation with fundamental frequency (F0), respectively. Conclusions: Formant tuning may be applied by a singer of the OM role, and both CF and OM role singers may use a rather pressed type of phonation, CF singers more than OM singers in the lower part of the pitch range. Most singers increased glottal adduction with rising F0.

Nonlinear Analyses of Elicited Modal, Raised, and Pressed Rabbit Phonation

The purpose of this study was to use nonlinear dynamic analysis methods such as phase space portraits and correlation dimension (D2) as well as descriptive spectrographic analyses to characterize acoustic signals produced during evoked rabbit phonation. Seventeen New Zealand white breeder rabbits were used to perform the study. A Grass S-88 stimulator (SA Instrumentation, Encinitas, CA) and constant current isolation unit (Grass Telefactor, model PSIU6; West Warwick, RI) were used to provide electrical stimulation to laryngeal musculature, and transglottal airflow rate and stimulation current (mA) were manipulated to elicit modal, raised intensity, and pressed phonations. Central 1 second portions of the most stable portion of the acoustic waveform for modal, raised intensity, and pressed phonations were edited and then analyzed via phase space portraits, Poincaré sections, and the estimation of the D2. In an attempt to limit the effects of the highly variable and nonstationary characteristics of some of the signals being analyzed, D2 analysis was also performed on the most stable central 200-millisecond portion of the acoustic waveform. Descriptive analysis of each phonation was also conducted using sound spectrograms. Results showed that the complexity of phonation and the subsequent acoustic waveform is increased as transglottal airflow rate and degree of glottal adduction are manipulated in the evoked rabbit phonation model. In particular, phonatory complexity, as quantified via D2 analyses and demonstrated via spectrographic characteristics, increases from "modal" (ie, phonation elicited at just above the phonation threshold pressure) to raised intensity (phonation elicited by increasing transglottal airflow rate) to pressed (phonation elicited by increasing the stimulation current delivered to the larynx). Variations in a single dynamic dimension (airflow rate or adductory force) resulted in significantly increased productions of nonlinear phenomenon, including bifurcations from periodicity to regions of subharmonic content, fundamental frequency, and harmonic jumps, and evidence of periodicity within aperiodic regions ("chaos"). The evoked rabbit phonation model described in this study allows for the elicitation of various types of phonations under controlled conditions and, therefore, has the potential to provide insight regarding important variables that may elicit examples of nonlinear phenomena such as subharmonics and deterministic chaos.

Vocal Economy in Vocally Trained Actresses and Untrained Female Subjects

Vocally trained actresses are expected to have more vocal economy than nonactresses. Therefore, we hypothesize that there will be differences in the electroglottogram-based voice economy parameter quasi-output cost ratio (QOCR) between actresses and nonactresses. This difference should remain across different levels of intensity. A total of 30 actresses and 30 nonactresses were recruited for this study. Participants from both groups were required to sustain the vowels /a/, /i/, and /u/, in habitual, moderate, and high intensity levels. Acoustic variables such as sound pressure level (SPL), fundamental frequency (F0), and glottal contact quotient (CQ) were obtained. The QOCR was then calculated. There were no significant differences among the groups for QOCR. Positive correlations were observed for QOCR versus SPL and QOCR versus F0 in all intensity levels. Negative correlation was found between QOCR and CQ in all intensity levels. Considering the differences among intensity levels, from habitual to moderate and from moderate to loud, only the CQ did not differ significantly. The QOCR, SPL, and F0 presented significant differences throughout the different intensity levels. The QOCR did not reflect the level of vocal training when comparing trained and nontrained female subjects in the present study. Both groups demonstrated more vocal economy in moderate and high intensity levels owing to more voice output without an increase in glottal adduction.