Stereoendoscopic observation of the larynx--vocal fold length in respiration and in phonation with vocal pitch change

Abstract

By use of a rigid stereoendoscope system, the vocal fold length in living human subjects was measured in absolute values. The subjects were seven adults. None of them had special training for singing. The measurements were made during inspiration and phonation with systematic changes in vocal pitch. During respiration, the glottal width was widened in inspiration and narrowed in expiration. Following the widening of the glottis, the vocal fold length increased and following the narrowing of the glottis, it decreased. In steady phonation with systematic changes in vocal pitch, the minimum length of the vocal fold ranged from 5.6 to 9.8mm in males and from 6.0 to 7.3mm in females. The range of maximum length was from 10.7 to 15.0mm in males and from 9.2 to 12.6mm in females. In male subjects, the vocal fold length in usual spoken pitch (USP) ranged from 8.9 to 11.3mm. In the female subjects, it ranged from 7.0 to 10.1mm. It is noted that the subjects having a larger value of the vocal fold length in USP, also have larger value in the minimum and maximum length of the vocal fold. There was a general tendency for vocal fold length to increase with pitch ascent at least within some portion of the voice range of spoken voice. The rate of the elongation in relation to the pitch ascent appears to be variable among the subjects. It is also noted that the vocal fold length does not necessarily increase with the increase in vocal pitch in the higher portion of the voice range, including both natural and falsetto registers. In these pitch ranges, the physiological mechanisms for pitch control might not consistently be seen in the change of the vocal fold length. It seems that these variabilities of relation between the vocal pitch and the vocal fold length are evident in spoken voice, while uniform patterns are dominantly seen in singing voice, although further research is needed to support this notion.