Historical Approaches in Revealing the Singing Voice, PART 1

Reviewing hundreds of years of history, this chapter details the development of means of visualizing the larynx and the vocal folds, and explores how these technologies influenced theories of voice production. Key investigators in vocal physiology are discussed, and their contributions put into context with modern understandings of voice production. These leaders helped bring about the growth of the field of laryngology, which occurred in parallel with improvements in laryngeal imaging. The chapter tracks these developments, starting with Garcia’s laryngeal mirror, then continues through the rest of the nineteenth and twentieth centuries. Among the innovations described are the use of stroboscopy to study the opening and closing vibratory pattern in different vocal registers; the development and application in Groningen of videokymography to examine fast and irregular vibratory events; and the development of VoceVista, a non-invasive tool which combines electroglottography with acoustical information on the sung production.

Typing Vocal Fold Vibratory Patterns in Excised Larynx Experiments Via Digital Kymography

Objectives Signal typing is central to the understanding of vocal fold vibratory patterns. Digital kymography (DKG) allows the direct observation of vocal fold vibratory patterns, and therefore, using DKG for vibratory signal typing may provide a useful complement to traditional signal typing techniques. Methods Video data collected from 20 larynges excised from mongrel dogs were observed with DKG in order to find examples of type 1 (nearly periodic), type 2 (subharmonic), and type 3 (aperiodic) vibratory patterns. The time series, frequency spectra, and correlation dimensions were calculated for each signal type. Results The type 1 pattern showed a periodic time series of glottal edges and a discrete frequency spectrum. The type 2 vibratory pattern displayed a time series of alternating high- and low-amplitude waves and a frequency spectrum that included a subharmonic (F0/2) frequency component. Regular and symmetric vibratory patterns were observed in the type 1 and type 2 patterns. The type 3 vibratory pattern was characterized by an aperiodic time series of glottal edges, a broadband frequency spectrum, and irregular and asymmetric vibratory patterns. The correlation dimension estimates increased from type 1 to type 2 to type 3. Conclusions Imaging with DKG demonstrated an ability to assign a signal type to various laryngeal vibrations. Signal typing techniques utilizing direct observation of the vocal folds could be useful in determining valid methods for the analysis of vocal fold vibrations.

Vocal fold injury following endotracheal intubation

Vocal fold scarring results in the formation of fibrous tissue which disturbs the vibratory pattern of the fold during phonation. However, vocal fold scarring in humans is poorly understood because of the lack of clear case reports focusing on voice quality. The authors present a case of vocal fold scarring with changes in voice quality. At the time of injury the pedicle mucosa was cemented with fibrin glue. Phonation was inhibited for two weeks and tranilast (300 mg/day) was given for 3 months. Sixty-nine days later, perceptual evaluation showed a normal result and the phonation time became better, but the mucosal vibration was still lacking. Ninety-seven days later, mucosal vibration was finally restored. We suggest that characterization of vocal fold scarring in humans may be different from that in animals, and recommend that surgical management should be avoided for at least three months after injury.

I. Internal Superior Laryngeal Nerve Afferent Activity during Respiration and Evoked Vocalization in Cats

The purpose of this project was to identify and categorize patterns of activity of the internal branch of the superior laryngeal nerve during vocalization evoked by midbrain stimulation in cats anesthetized with α-chloralose. Unit activity was isolated from the cut distal end of the internal branch of the superior laryngeal nerve by means of floating bipolar electrodes that retained their contact with nerve fibers despite movement due to vocalization. The phases of respiration and vocalization were determined with a diaphragm electromyogram, a photoglottogram, and a microphone recording. Five groups of discrete afferent activities were defined according to relationships between the spike activity and the phases of vocalization. Group 1 cell activity peaked just before phonation, during expiratory airflow (n = 26). Group 2 cells (n = 19) followed a vocal fold vibratory pattern during phonation. Group 3 cell activity (n = 6) peaked during phonation, but did not follow vocal fold vibration. Group 4 cells (n = 3) were active during inspiration between phonations. Group 5 cells (n = 4) showed both inspiratory and expiratory modulation. These results indicate that laryngeal afferent activity responds to phonation-specific events during vocalization. This stereotyped afferent information might be used by the central nervous system to modulate vocalization.

Microvascular Lesions of the True Vocal Fold

Microvascular lesions, also called varices or capillary ectasias, in contrast to vocal fold polyps with telangiectatic vessels, are relatively small lesions arising from the microcirculation of the vocal fold. Varices are most commonly seen in female professional vocalists and may be secondary to repetitive trauma, hormonal variations, or repeated inflammation. Microvascular lesions may either be asymptomatic or cause frank dysphonia by interrupting the normal vibratory pattern, mass, or closure of the vocal folds. They may also lead to vocal fold hemorrhage, scarring, or polyp formation. Laryngovideostroboscopy is the key in determining the functional significance of vocal fold varices. Management of patients with a varix includes medical therapy, speech therapy, and occasionally surgical vaporization. Indications for surgery are recurrent hemorrhage, enlargement of the varix, development of a mass in conjunction with the varix or hemorrhage, and unacceptable dysphonia after maximal medical and speech therapy due to a functionally significant varix.

A Subharmonic Vibratory Pattern in Normal Vocal Folds

This study observes in detail an F 0 /2 (sounding an octave below an original tone) subharmonic vibratory pattern produced in a normal larynx. Simultaneous electroglottographic and photoglottographic measurements reveal two different open phases within a subharmonic cycle—the first shorter with a simple shape, the second longer with a shape containing a “ripple.” Such parameters as the large open quotient (ca. 0.8) and the high airflow values (ca. 1000 cm 3 /s) distinguish this phonation from the vocal fry (pulse) register. Using an electronic divider to track the subharmonic frequency, a method has been developed to observe the subharmonic vibration of the vocal folds stroboscopically. The stroboscopic visualization reveals an unusual mucosal movement during the “ripple,” characterized by an opening movement of the upper margins, which interrupts the closing movement of the vocal folds. An explanation is offered that this vibratory pattern arises as a consequence of detuning of the usually identical frequencies of the dominant modes of the vocal folds, with 3:2 entrainment replacing the normal 1:1 pattern.