Glottal closure in the hemiparalyzed canine larynx.

Although compensation of voice with unilateral recurrent laryngeal nerve paralysis is commonly held to be the result of the unaffected vocal fold crossing past midline, or overcrossing, this mechanism of compensation has rarely been documented accurately. Beagle dogs were used to create a model of another proposed mechanism of compensation, known as midline drift. Six animals underwent sectioning of the left recurrent laryngeal nerve. One week later, three of the dogs underwent removal of the left posterior and lateral cricoarytenoid muscles. The effects of these procedures were studied by subjective assessment, direct laryngoscopy, and sound spectrographic analysis. Results indicate that glottal closure was improved after the second surgical procedure. The clinical implications of the results are discussed and compared with other manners of compensation hypothesized in the literature.

H-Index: a new measure of glottal efficiency for the pathologic voice.

Taking advantage of the extended dynamic range of digital analysis of voice the H-Index represents the first proposed acoustical measure of glottal efficiency. "Hi" /hai/ was chosen to evaluate glottal efficiency since it provides an excellent test of glottal transformation from voiceless to voiced sound energy, the upper vocal tract having a neutral effect. Fifteen individuals with normal voices and 30 patients with hoarse voices were asked to say "hi." The power ratio of /h/ to /a/ was calculated from peak power of each measure from the power envelope. Voice quality had a highly significant effect on measured values (P < .001). A high degree of correlation (P < .001) was found with the AC/DC ratio, a standard aerodynamic measure of glottal efficiency. The results indicate that the H-Index represents an excellent measure of glottal efficiency, obviating the need of invasive techniques or expensive, highly specialized equipment.

High-frequency power ratio of breathy voice.

Digital technological advances have made detailed voice analysis possible. This report proposes, with the use of such equipment, a new method of quantifying differences in the high-frequency content of normal and breathy voices. The high-frequency power ratio, a ratio of high-frequency power versus total power, was calculated as the lower limit of the high-frequency range (Fc) and varied from 1 to 10 kHz. The high-frequency power ratio values of two groups, 16 normal and 24 breathy voice individuals, were then compared. Three breathy individuals were also studied after type I thyroplasty. High-frequency power ratio values measured at an Fc of 6 kHz significantly separated normal from breathy voices. The specifications provided are appropriate for both the commercial voice lab and for clinical resources. Furthermore, a high-frequency power ratio (6 kHz) is a useful tool for the evaluation of phonosurgery.