No abstract

No abstract

No abstract

No abstract

The relationship between the voice intensity (sound pressure level), the subglottic pressure, the air flow rate, and the glottal resistance was investigated. Simultaneous recordings were made of the sound pressure level of voice, the subglottic pressure, the flow rate, and the volume of air utilized during phonation. The glottal resistance, the subglottic power, and the efficiency of voice were calculated from the data. It was found that on very low frequency phonation the flow rate remained almost unchanged or even slightly decreased with the increase in voice intensity while the glottal resistance showed a tendency to augment with increased voice intensity. In contrast to this, the flow rate on high frequency phonation was found to increase greatly, while the glottal resistance remained almost unchanged as the voice intensity increased. On the basis of the data it was concluded that at very low pitches, the glottal resistance is dominant in controlling intensity (laryngeal control), becoming less so as the pitch is raised, until at extremely high pitch the intensity is controlled almost entirely by the flow rate (expiratory muscle control).

This paper reviews progress in laryngeal framework surgery since it was first reported about 25 years ago. The success of this type of surgery requires both a basic knowledge of the physiology of phonation, in order to make decisions about the surgical procedure, and surgical skill, in order to accomplish the intended procedure successfully. The main reason for hoarseness is imperfect closure of the glottis, but the second most important reason for hoarseness, increased stiffness of the vocal fold, cannot be corrected by mere medialization of the vocal fold. Laryngeal framework surgery is different in concept from conventional surgery, which is intended to remove the lesion. Controversial points discussed here regarding type I thyroplasty include: (i) whether the cartilage window should be removed; (ii) materials for fixation of the window; and (iii) comparison of type I thyroplasty with arytenoid adduction. A new surgical treatment for spasmodic dysphonia and its results in three patients are described briefly. Surgery for raising the vocal pitch requires further improvement. In the future, laryngeal framework surgery will have wider application in treatment of dysphonias, such as asthenic voice due to atrophy in professional singers or aging, pitch problems in females and gender identity disorder and spasmodic dysphonia.

The effects of asymmetrical tension on the vibratory pattern of the vocal cords were studied in two kinds of experiments: 1) high speed motion picture photography of artificial voice production in excised canine and human larynges, and 2) computer synthesis of voice and vocal cord vibration via a theoretical model incorporating the physiological parameters required for phonation. In both approaches the asymmetrically tensed vocal cords consistently vibrated in three distinct modes which depend partly on the rest positions of the vocal cords; Type I. For rest positions at or near closure, the two cords vibrate at the same frequency with glottal closure every period, and with tense cord preceding the lax one in phase and with the line of contact moving toward the tenser cord during the closed phase. The voice produced is not hoarse; Type II. For wider rest positions glottal closure occurs irregularly, the vibrations become complex and less periodic, and the voice becomes hoarse; Type III. The glottis never closes and the vibrations become more periodic with reduced amplitude. Supplementary stroboscopic observations suggest a precedure for diagnosing tension asymmetry and the implications for surgical treatment for disorders of vocal pitch are discussed.

A dynamic model of the vocal cords, namely, a bilaterally symmetric two-mass model, is extended to a bilaterally asymmetric two-mass model to simulate pathological conditions of the vocal cords. Asymmetric behavior of the computer model is investigated for various conditions of imbalance in bilateral tension. The computer model is found to behave in three basic vibratory modes that are similar to those observed in physiological experiments on larynges under tension imbalance. The three distinctive modes are (1) a vibratory pattern with differences in phase and amplitude of cord vibration; (2) a nearly periodic motion without glottal closure; and (3) an unsteady, dicrotic or tricrotic motion. The three modes are found to be a strong function of the subglottal pressure and the glottal rest area, as well as the imbalance conditions of the cord parameters. The asymmetric vocal-cord model is incorporated into a dynamic vocal-tract synthesizer to simulate speech with a hoarse voice. Subject Classification: [43]70.20, [43]70.50.