Pitch altering Phonosurgery in Trans sexual or Transgender individuals

(Voice Feminization Surgery: A Critical Overview By Anne A. Lawrence, M.D., Ph.D).

Male and female voice differ primarily in their pitch (frequency) and in their timbre (resonance). The characteristic pitch or fundamental frequency (F0) of the male voice ranges from about 100 to 150 Hz; for the female voice, F0 ranges from 170 to 220 Hz. The lower pitch of the male voice is primarily due to the greater length and mass of the male vocal cords. The distinctive timbre or resonance of the male voice is primarily due to the greater length of the male upper airway (throat, mouth, nose, and sinuses; see Fitch & Giedd, 1999). Both fundamental frequency and resonance provide important acoustic cues to the sex of a speaker, but fundamental frequency is the more important cue (for a review see Oates & Dacakis, 1983). There is currently no practical way to surgically feminize the resonant properties of the airway (more research in this area would be desirable), but there are several operations that can surgically modify the pitch or F0 of the voice.
Fundamental frequency, F0, is inversely proportional to the length of the vocal cords, is inversely proportional to the square root of the density (mass per unit volume) of the cords, and is directly proportional to the square root of the tension of the cords (see Kunachak, Prakunhungsit, & Sujjalak, 2000). Consequently, there are really only three ways to attempt to increase F0 surgically: (a) by decreasing the vibrating length of the vocal cord (highly efficient), (b) by increasing tension of the vocal cord (less efficient, since the relationship is square root rather than linear), or (c) by decreasing the density of the vocal cord (also less efficient, since the relationship is square root).

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