Pitch can also be altered through voice resonance modification. The length of the vocal tract affects the resonance of the vocal tract, which in turns affects the pitch. Cis men tend to have vocal tracts that are 10-20% larger than those of cis women, and therefore cis men have a lower vocal tract resonance, and a lower pitch, than cis women. Modifying the length of a vocal tract results in a change in resonance and in pitch, as can be shown by saying the sound “sss” and protruding and retracting the lips. Transgender women can use techniques, such as retracting the lips, to shorten the vocal tract and sound more feminine.