A Comparison of Two Methods of Formant Frequency Estimation for High-Pitched Voices

This study sought to compare formant frequencies estimated from natural phonation to those estimated using two methods of artificial laryngeal stimulation: (1) stimulation of the vocal tract using an artificial larynx placed on the neck and (2) stimulation of the vocal tract using an artificial larynx with an attached tube placed in the oral cavity. Twenty males between the ages of 18 and 45 performed the following three tasks on the vowels /a/ and /i/: (1) 4 seconds of sustained vowel, (2) 2 seconds of sustained vowel followed by 2 seconds of artificial phonation via a neck placement, and (3) 4 seconds of sustained vowel, the last two of which were accompanied by artificial phonation via an oral placement. Frequencies for formants 1-4 were measured for each task at second 1 and second 3 using linear predictive coding. These measures were compared across second 1 and second 3, as well as across all three tasks. Neither of the methods of artificial laryngeal stimulation tested in this study yielded formant frequency estimates that consistently agreed with those obtained from natural phonation for both vowels and all formants. However, when estimating mean formant frequency data for samples of large N, each of the methods agreed with mean estimations obtained from natural phonation for specific vowels and formants. The greatest agreement was found for a neck placement of the artificial larynx on the vowel /a/.     

A physiological and acoustic study on voiced bilabial fricative /β:/ as a vocal exercise

The voiced bilabial fricative /β:/ has been used as a vocal exercise. The present study investigated the effects of the exercise on voice production and voice source. This study compared vowel phonation on the syllable /a:p/ with the production of the exercise and vowel phonation before and immediately after the exercise. The methods were (a) dual-channel electroglottography, from which the vertical laryngeal position was derived, (b) electromyography using surface electrodes, and (c) inverse filtering of the acoustic signal to obtain an estimate of the voice source. In the production of /β:/ as compared with vowel phonation in most of the cases, the vertical laryngeal position seemed to be higher, the muscular activity of the larynx lower, and the slope of the voice source spectrum steeper. In vowel phonation after the exercise, the muscular activity seemed to be lower in most cases, although the voice source remained unchanged. This seems to indicate improved vocal economy.     

Gender comparisons of children's vocal fold contact behavior

Vocal fold contact behavior was examined in separate groups of boys and girls through application of an electroglottograph(EGG). In general, a contact quotient (EGG duty cycle) showed minimal differences within and between boys and girls during sustained production of the vowels /i/, /u/, and /a/. The findings are discussed with respect to the laryngeal behavior of prepubescent children as well as the clinical utility and applicability of the EGG for examining phonatory behavior among young children.     

The Aged Voice: A New Hypothesis

The anatomical changes in the senescent larynx are presented, with particular reference to the nonlinearity model of laryngeal biomechanics. The behavior of the Ishizaka-Flanagan 2-mass model in geriatric phonation suggests that an increase in nonlinearity can explain a number of disparate observations about the aged voice. Biomechanical assessment of real laryngeal tissue and experimentation in vivo is needed to confirm the hypothesis, leading to better paradigms of some phonatory disorders and perhaps to novel treatments.     

Physiological aspects of a vocal exercise

The physiological aim of vocal exercises is mostly understood in intuitive terms only. This article presents an attempt to document the phonatory behavior induced by a vocal exercise. An elevated vertical position of the larynx is frequently associated with hyperfunctional phonatory habits, presumably because it induces an exaggerated vocal fold adduction. Using the multichannel electroglottograph (MEGG), the laryngeal position was determined in a group of subjects who performed a voice exercise that contained extremely prolonged versions of the consonant /b:/. This exercise is used by the coauthor (N.E.) as part of a standard vocal exercise program. Two of the seven subjects were dysphonic phonastenic patients, and the rest were normal trained or untrained persons. Different attempts to calibrate the MEGG confirmed a linear relationship with larynx height, provided electrode positioning was correct. The results showed that the exercise induced substantial vertical displacements of the larynx. Comparison with larynx height during voicing of other consonants showed that the /b/, in particular, tended to lower the larynx.     

On the influence of laryngeal pathologies on acoustic and electroglottographic jitter measures

This study compared acoustic and electroglottographic (EGG) jitter from [a] vowels of 103 dysphonic speakers. The EGG recordings were chosen according to their intensity, signal-to-noise ratio, and percentage of unvoiced intervals, while acoustic signals were selected based on voicing detection and the reliability of jitter extraction. The agreement between jitter measures was expressed numerically as a normalized difference. In 63.1% (65/103) of the cases the differences fell within +/-22.5%. Positive differences above +22.5% were associated with increased acoustic jitter and occurred in 12.6% (13/103) of the speakers. These were, typically, cases of small nodular lesions without problems in the posterior larynx. On the other hand, substantial rises in EGG jitter leading to differences below -22.5% took place in 24.3% (25/103) of the speakers and were related to hyperfunctional voices, creaky-like voices, small laryngeal asymmetries affecting the arytenoids, or small-to-moderate glottal chinks. A clinically relevant outcome of the study was the possibility of detecting gentle laryngeal asymmetries among cases of large unilateral increase in EGG jitter. These asymmetries can be linked with vocal problems that are often overlooked in endoscopic examinations.     

Fundamental Frequency Change During Offset and Onset of Voicing in Individuals with Parkinson Disease

SUMMARY: After years of treatment with the medication levodopa, most individuals with Parkinson disease (PD) experience fluctuations in response to their medications. Although relatively consistent perceptual voice improvements have been documented to correspond with these fluctuations, consistent quantitative data to support this finding are lacking. This mismatch may have occurred because most of this phonation research has centered on long-term phonatory measures (ie, across speaking samples and prolonged vowel tasks). The current study examined short-term phonatory behavior in individuals with PD, specifically examining fundamental frequency (F0) at the offset and onset of phonation, before and after a voiceless consonant. The F0 analysis at phonatory offset supported the conclusion that individuals with PD have difficulty with the rapid offset of voicing, and that they are stopping vocal fold vibration primarily through vocal fold abduction (without adding tension). The F0 analysis at phonatory onset revealed that all groups use some laryngeal tension at the initiation of voicing. The tension was lowest for the PD participants who were in their OFF medication state, and it was highest for the age-matched control participants and the PD participants in their ON medication states.     

Phonatory characteristics of excised pig, sheep, and cow larynges

The purpose of this study was to examine the phonatory characteristics of pig, sheep, and cow excised larynges and to find out which of these animal species is the best model for human phonation. Excised pig, sheep, and cow larynges were prepared and mounted over a tapered tube on the excised bench that supplied pressurized, heated, and humidified air in a manner similar to that for excised canine models. Each excised larynx was subjected to a series of pressure-flow experiments with adduction as major control parameter. The subglottal pressure, electroglottograph (EGG), mean flow rate, audio signal, and sound pressure level were recorded during each experiment. EGG signal was used to extract the fundamental frequency. It was found that pressure-frequency relations were nonlinear for these species with large rate of frequency changes for the pig. The average oscillation frequencies for these species were 220+/-57 Hz for the pig, 102+/-33 Hz for the sheep, and 73+/-10 Hz for the cow. The average phonation threshold pressure for the pig was 7.4+/-2.0 cm H(2)O, 6.9+/-2.9 cm H(2)O for the sheep, and 4.4+/-2.3 cm H(2)O for the cow.     

On the relation between the dimensions and resonance characteristics of the vocal tract: a study with MRI.

The relation between the spatial configuration of the vocal tract as determined by magnetic resonance imaging (MRI) and the acoustical signal produced was investigated. A male subject carried out a set of phonatory tasks, comprising the utterance of the sustained vowels /i/ and /a/, each in a single articulation, and the vowel /epsilon/ with his larynx positioned variously on a vertical axis. Two- and three-dimensional measurements of the vocal tract were performed. The results of these measurements were used to calculate resonance frequencies, according to predictions from acoustical theory. Finally, calculated frequencies were compared with actually measured resonance frequencies in the audio signal. We found a strong relation between the acoustical signal produced and the spatial configuration for the first resonance frequencies of the articulations of the vowel /epsilon/, and first two resonance frequencies of the vowels /a/ and /i/. The capability to determine accurately vocal tract dimensions is a major advantage of this imaging technique.     

Significance of mechanoreceptors in the subglottal mucosa for subglottal pressure control in singers

According to Wyke and Kirchner (Wyke B, Kirchner J. Neurology of the larynx. In: Hinchcliffe R, Harrison D, eds. Scientific foundation of otolaryngology. London: William Heinemann Medical Books, 1976:546–66) mechanoreceptors in the subglottal mucosa play a significant role in the control of laryngeal muscle activity in response to changes of subglottal pressure during phonation. In singers this pressure is adapted not only to phonatory loudness but also to fundamental frequency. By spraying Xylocaine solution with a needle inserted into the trachea through the anterior gap between the cricoid and thyroid cartilages, the subglottal mucosa was anesthetized in three singers. The effects on subglottal pressure and fundamental frequency of this anesthesia were examined. The pressure effects varied between the subjects, whereas the fundamental frequency accuracy was adversely affected in all three subjects. The implications of these findings are discussed.     

Relationship between aerodynamic measures of glottal efficiency and stroboscopic findings in asymptomatic singing students

Singing requires exquisite coordination between the respiratory and phonatory systems to efficiently control glottal airflow. Asymptomatic singing students underwent pulmonary function testing (PFT), videostrobolaryngoscopic examination, and measures of glottal efficiency (maximum phonation time [MPT], glottal flow rate [GFR], and phonation quotient [PQ]) performed in both a sung and spoken tone. Pulmonary function and glottal efficiency values were within reported normative data for professional singers. However, sung tones were made with significantly higher GFR and PQ and lower PQ than spoken tones. The mean GFR was not related to the degree of glottal closure (by videostrobolaryngoscopy) or underlying pulmonary support.     

Effect of Fasting on Voice in Women

OBJECTIVE/HYPOTHESIS: To study the effect of fasting on voice in women: abstinence from food and water intake between 14 and 18 hours. STUDY DESIGN: A prospective study on female subjects. MATERIAL AND METHOD: A total of 28 female subjects were included in this study. Their age ranged between 21 and 45 years. Subjects with vocal symptoms or vocal fold lesions were excluded. The subjects were tested when they were not fasting and while fasting after the first week of intermittent fasting during Ramadan. Each subject was first asked about her vocal symptoms and the ease of phonation or phonatory effort. Then each underwent acoustic analysis and laryngeal video-endostroboscopy. RESULTS: Vocal fatigue was the most common reported complaint (53.6%) followed by deepening of the voice (21.4%) and harshness (10.2%). Self-reported phonatory effort was significantly affected by fasting (P value < 0.001). Out of the 28 subjects, 23 had an increase in their phonatory effort. Vocal acoustic parameters did not change markedly except for the maximum phonation time, which decreased significantly. Laryngeal video-endostroboscopy did not reveal any significant changes during fasting. All stroboscopic parameters were the same except for a decrease in the amplitude of the mucosal waves in one subject and the presence of a posterior chink in three subjects. CONCLUSION: Fasting affects voice. There is an increase in the phonatory effort, and vocal fatigue is the most common symptom.     

Effects of laryngeal endoscopy on the vocal performanceof young adult females with normal voices

This study investigated changes in maximum phonation time andacoustic and perceptual measures of voice following topical anesthesia and laryngeal endoscopy with the flexible endoscope. Forty-four females, aged 18–33 years and with normal voices, performed four vocal tasks: (a) 3-second /i/ prolongation, (b) maximum phonation time on /i/, (c) stepwise scale-singing, and (d) reading a standard passage. Subjects performed these tasks prior to anesthesia, after anesthesia, and again during laryngeal endoscopy. Voice samples were analyzed for jitter, shimmer, harmonic-to-noise ratio, speaking fundamental frequency, maximum phonational frequency range, maximum phonation time, harshness, and breathiness. Results demonstrated significant reductions in maximum phonational frequency range following anesthesia and, during laryngeal endoscopy, reductions in maximum phonation time and increases in speaking fundamental frequency, minimum fundamental frequency on scale-singing, and breathiness. Clinicians using laryngeal endoscopy for evaluation and management of vocal dysfunction should, therefore, consider the possible effects of these procedures on vocal functioning.     

Effects of Inhalatory Abdominal Wall Movement on Vertical Laryngeal Position During Phonation

The configuration of the body resulting from inhalatory behavior is sometimes considered a factor of relevance to voice production in singing and speaking pedagogy and in clinical voice therapy. The present investigation compares two different inhalatory behaviors: (1) with a "paradoxical" inward movement of the abdominal wall, and (2) with an expansion of the abdominal wall, both with regard to the effect on vertical laryngeal position during the subsequent phonation. Seventeen male and 17 female healthy, vocally untrained subjects participated. No instructions were given regarding movements of the rib cage. Inhaled air volume as measured by respiratory inductive plethysmography, was controlled to reach 70% inspiratory capacity. Vertical laryngeal position was recorded by two-channel electroglottography during the subsequent vowel production. A significant effect was found; the abdomen-out condition was associated with a higher laryngeal position than the abdomen-in condition. This result apparently contradicted a hypothesis that an expansion of the abdominal wall would allow the diaphragm to descend deeper in the torso, thereby increasing the tracheal pull, which would result in a lower laryngeal position. In a post-hoc experiment including 6 of the subjects, body posture was studied by digital video recordings, revealing that the two inhalatory modes were clearly associated with postural changes affecting laryngeal position. The "paradoxical" inward movement of the abdominal wall was associated with a recession of the chin toward the neck, such that the larynx appeared in a lower position in the neck, for reasons of a postural change. The results suggest that the laryngeal position can be affected by the inhalatory behavior if no attention is paid to posture, implying that instructions from clinicians and pedagogues regarding breathing behavior must be carefully formulated and adjusted in order to ensure that the intended goals are reached.     

Differential diagnosis of spasmodic dysphonia: A kinematic perspective

Although originally considered an hysterical functional disorder, spasmodic dysphonia (SD) appears to be a heterogeneic symptom complex that is associated with several neurological diseases. Perceptual, acoustic, and electromyographic studies have not clearly differentiated the underlying pathologies that result in spasmodic phonatory dysfunction. Kinematic analysis of documented laryngeal examinations during phonation and respiration indicates that particular different movement disorders affect laryngeal function and are associated with spasmodic phonatory characteristics. The particular features of dystonia, tremors, myoclonus, and progressive supranuclear pathology should be recognized, since they may present with disease focal to the laryngeal muscles. Other movement disorders may also be associated with spasmodic phonatory abnormalities, but are less likely to be focal. Treatment of SD signs and symptoms is more likely to be successful and assessments of treatment more likely to be meaningful if the underlying pathophysiology of spasmodic phonatory behavior is identified.     

Acoustic analysis of voice in individuals with amyotrophic lateral sclerosis and perceptually normal vocal quality

Currently, early phonatory changes in amyotrophic lateral sclerosis(ALS) are not well understood. The aim of this study was to compare acoustic parameters of voice in ALS subjects who demonstrated perceptually normal vocal quality on sustained phonation with a control group. We hypothesized that objective analysis of voice would reveal significant differences on specific acoustic parameters of voice compared to the control group. Results revealed statistically significant differences between the two groups on measures related to frequency range and phonatory stability. The findings suggest that early bulbar signs affecting the laryngeal system may be present in patients with ALS before the occurrence of perceptually aberrant vocal characteristics.     

Problems and pitfalls of electroglottography

The popularity and usefulness of the electroglottograph (EGG) has increased remarkably since its introduction over a decade ago. It has been used to measure fundamental frequency of phonation, fundamental frequency perturbation, details of the vocal fold vibratory cycle, as well as to provide an indication of laryngeal vertical movement. It has also been used with a variety of speech and voice disorders. The EGG is not without its limitations and problems. Some of these are found in the electronic designs of specific instruments, whereas other problems are related to subject characteristics, the placement of the electrodes, electrode symmetry, and subject/instrument interaction. This article explores some of these concerns, primarily from the perspective of two individuals who have used the EGG extensively with children, men and women, voice patients, stutterers, and neurologically impaired persons. Some of the concerns to consider and pitfalls to avoid in the interpretation and measurement of EGG signal are discussed.     

Electroglottographic quasi-open quotient and amplitude in crescendo phonation

Crescendo phonation (swelltone) was used to evaluate the laryngeal tensioning behavior of seven normal speakers and of 12 dysphonic patients. EGG quasi-open quotient (qOq), stroboscopic open quotient, and vocal sound pressure level (SPL) were measured, and EGG amplitude and the mucosal wave were assessed qualitatively. For normal speakers, the qOq decreased greatly as vocal intensity increased. The same tendency was observed, but to a lesser extent, among hyperfunctional dysphonics. In contrast, qOq increased with vocal intensity among the hypofunctional dysphonics. The crescendo task combined with EGG assessment appears to offer a valid approach to the classification of laryngeal dysfunctions.     

Fundamental Frequency in Speakers of Portuguese for Different Voice Samples

The purpose of this research was to obtain information on the mean fundamental frequency (Fo) levels of Portuguese speakers and to investigate (1) whether differences exist between two groups with different voice qualities (normal and dysphonia), genders, ages, and speech tasks; and (2) which variables contribute to the variance. To this end, 109 subjects (52 dysphonics and 57 controls) participated in the study. Speech material included three sustained vowels ([u], [i], and [a]), a standard written passage, and a conversation produced at a comfortable conversational pitch and loudness level. Electroglottographic (EGG) data were obtained. Although the results show that, overall, the dysphonics had lower Fo than did controls for all speaking conditions, and that there were differences according to age, these contrasts were not statistically significant. Gender and speech task effects were statistically significant. Additionally, the mean Fo variance is explained by a high prediction model (between 59% and 73%).     

Neuroanatomical model for laryngeal operation

The focus of this presentation is on the development of a neuroanatomical model underlying laryngeal function. It is suggested that the model can be used as an aid to the understanding of the structures that support phonatory output as well as a basis for physiological research on the nature of voice production. Although the postulates are anatomically grounded, the approach utilized also shows that there is ongoing feedback during phonation and, hence, that both the motor and sensory (neural) networks are coordinated during any phonatory activity. Additionally, the discussion serves to review the neuroanatomical interface between respiration and voice.