Examining the Effect of Volitionally Altering Fundamental Frequency on Measures Associated With Vocal Hyperfunction.

Speech-language pathologists who work with transgender and nonbinary individuals are often concerned about introducing vocal hyperfunction (VH) while supporting the use of a more gender-congruent voice. The current study examined the effects of volitionally altering fundamental frequency (fo) on measures associated with VH. Forty (20 female, 20 male) speakers with no vocal complaints and who did not identify as transgender were recruited. Speakers were recorded in two conditions: habitual fo and altered fo. In the altered fo condition, speakers volitionally altered their fo by two semitones in the stereotypical direction desired by transgender and nonbinary speakers with the same vocal anatomy: females lowered their fo and males raised their fo. A total of 13 acoustic, aerodynamic, videostroboscopic, and perceptual (self- and other) measures were assessed. Of the 13 measures, 7 were statistically affected by the two-way interaction between sex and fo condition. Only three measures had medium or larger effect sizes. Compared to using a habitual fo, females used longer vocal tract lengths, and higher smoothed cepstral peak prominences (CPPS) and low to high (L/H) ratios when lowering fo and males used shorter vocal tract lengths and lower L/H ratios when raising fo. In general, vocalizations produced with a volitionally altered fo were more consistent with those in speakers with VH than vocalizations produced with a habitual fo. In response to altering fo, females had more measures that differed than males. This is counter to expectations given that males raised their fo and using a higher fo is associated with increased laryngeal tension. That being said, many of the changes reflected the physiological adjustments required to achieve an externally specified fo target.