<P> The perceived pitch of a person's voice is determined by a number of different factors, most importantly the fundamental frequency of the sound generated by the larynx . The fundamental frequency is influenced by the length, size, and tension of the vocal folds . This frequency averages about 125 Hz in an adult male, 210 Hz in adult females, and over 300 Hz in children . Depth - Kymography is an imaging method to visualize the complex horizontal and vertical movements of vocal folds . </P> <P> The vocal folds generate a sound rich in harmonics . The harmonics are produced by collisions of the vocal folds with themselves, by recirculation of some of the air back through the trachea, or both . Some singers can isolate some of those harmonics in a way that is perceived as singing in more than one pitch at the same time--a technique called overtone singing or throat singing such as in the tradition of Tuvan throat singing . </P> <P> Wound healing is a natural regeneration process of dermal and epidermal tissue involving a sequence of biochemical events . These events are complex and can be categorized into three stages: inflammation, proliferation and tissue remodeling . The study on vocal fold wound healing is not as extensive as that on animal models due to the limited availability of human vocal folds . Vocal fold injuries can have a number of causes including chronic overuse, chemical, thermal and mechanical trauma such as smoking, laryngeal cancer, and surgery . Other benign pathological phenomena like polyps, vocal fold nodules and edema will also introduce disordered phonation . </P> <P> Any injury to human vocal folds elicits a wound healing process characterized by disorganized collagen deposition and, eventually, formation of scar tissue . Verdolini and her group sought to detect and describe acute tissue response of injured rabbit VF model . They quantified the expression of two biochemical markers: interleukin 1 and prostaglandin E2, which are associated with acute wound healing . They found the secretions of these inflammatory mediators were significantly elevated when collected from injured VF versus normal VF . This result was consistent with their previous study about the function of IL - 1 and PGE - 2 in wound healing . Investigation about the temporal and magnitude of inflammatory response in VFs may benefit for elucidating subsequent pathological events in vocal fold wounding, which is good for clinician to develop therapeutic targets to minimize scar formation . In the proliferative phase of VFs wound healing, if the production of HA and collagen is not balanced, which means the HA level is lower than normal, the fibrosis of collagen cannot be regulated . Consequently, regenerative - type wound healing turns to be the formation of scar . Scarring may lead to the deformity of vocal fold edge, the disruption of LPs viscosity and stiffness . Patients suffering from vocal fold scar complain about increased phonatory effort, vocal fatigue, breathlessness, and dysphonia . Vocal fold scar is one of the most challenging problems for otolaryngologists because it's hard to be diagnosed at germinal stage and the function necessity of VF is delicate . </P>

During phonation abduction of the vocal folds is a function of