Head size (hs) option is specified as the average size for an adult man (if sx = 1) or an adult woman (if sx = 0). A head size of 100% is normal or average for a given sex, but people can differ significantly in this characteristic. Head size has a strong influence on a person's voice. Large musical instruments produce low notes, and humans with large heads tend to have low, resonant voices. For example, to make Paul sound like a larger man with a 15% longer vocal tract (and formant frequencies that are scaled down by a factor of about 0.85%), use the following command:
[:np][:dv hs 115] Do I sound more like huge Harry this way?
Head size is one of the best variables to use if you want to make dramatic voice changes. For example, Paul has a head size of 100, while Harry's deep voice is caused in part by a head-size change to 115, or 15% greater than normal. Decreasing head size produces a higher voice, such as in a child or adolescent. Extreme changes in head size, as in the following examples, are somewhat difficult to understand.
[:nh][:dv hs 135] Do I have a swelled head?
[:nk] I am about 10 years old.
[:nk][:dv hs 65] Do I sound like a six year old?
Note
Extreme changes in head size can cause overloads, as well as difficulties in understanding the speech. The modification of certain options such as f4, f5, and g1 can help to correct this problem.