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Briana Figallo, Sally Gallena, Ph.D.

The Effect of Speech Therapy on Vowel Formant Frequencies in Transgender Male-to-Female Speakers


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The research described in this abstract is the continuation of a pilot study which occurred from November 2014 through April 2015. Preliminary results of the pilot study were shared at the 2015 Emerging Scholars event as well as the 2015 American Speech-Language-Hearing Association convention. Through the pilot study, weaknesses in study design, protocol, and treatment fidelity were identified and addressed for a re-launch of the study which occurred over the fall 2015 semester with one new participant. A brief summary of the study’s purpose, research questions, methods, and results are described below.

For male-to-female (MtF) transgender speakers, achieving voice that matches their desired gender is a critical component of a successful gender transition, yet it is one of the most difficult components of the transition to achieve. Current research on this topic suggests that increasing F0 to a feminine range is the most salient factor in achieving feminine voice, but raising F0 in and of itself is often not sufficient to give the perceptual impression of a female speaker (Gelfer & Mikos, 2005; Gelfer & Schofield, 2000; Hillenbrand & Clark, 2009; King, Brown, & McCrea, 2011; Skuk & Schweinber, 2014). Some research suggests that vowel formant frequencies need to be increased as well as pitch in order to give the perception of feminine voice (Adler, Hirsch, & Mordaunt, 2012; Gelfer & Bennett, 2013; Hillenbrand & Clark 2009; Mount & Salmon, 1988).

However, an explicit relationship between a rise in F0 and its effect on vowel formant frequencies has not been established. Additionally, the ability of MtF speakers to raise vowel formant frequencies through speech therapy lacks conclusive evidence. Thus, the purpose of this study was twofold and investigated the following research questions:

1) Do MtF vowel formants F1-F3 automatically align with female vowel formant ranges when F0 increases to a feminine range?

2) Can MtF speakers change vowel formants F2-F3 to align with female vowel formant ranges by purposefully adjusting articulator placement?

This single subject study utilized a multiple baseline, AB design. The participant was a transgender MtF individual receiving voice therapy at the Loyola University Maryland Clinical Center in Columbia, MD. A revised three-phase protocol including evidence-based practices was implemented to improve treatment fidelity and correct limitations exposed in the pilot study. The participant attended weekly therapy sessions targeting increased pitch to a feminine range and, subsequently, articulator adjustment (i.e., forward tongue position and lip retraction) to raise vowel formant frequencies. The participant recorded weekly speech samples consisting of syllables in the /h/+ /vowel/+ /d/ format (e.g., “heed”, “had”, “hod”, etc.) and The Rainbow Passage (Fairbanks, 1969). These recordings were analyzed via PRAAT software to determine changes in the participant’s vowel formants F1, F2 and F3 as the participant increased F0 and altered tongue and lip postures to mimic a female vocal tract.

Graphical representations of the data were created, visually inspected, and compared to the pilot study. Results varied by vowel and vowel formant, but overall observations can be made regarding each research question. The data suggests that vowel formants did not automatically align with female vowel formant ranges when F0 reached a feminine range. However, for certain vowels, articulation modifications were successful in helping transgender MtF participants produce vowel formants that are more closely aligned with female vowel formant ranges.


Adler, R. K., Hirsch, S., & Mordaunt, M. (2012). Voice and communication therapy for the transgender/transsexual client: A comprehensive clinical guide (2nd ed.). San Diego, CA: Plural Publishing.

Gelfer, M. P., & Bennett, Q. E. (2013). Speaking fundamental frequency and vowel formant frequencies: Effects on perception of gender. Journal of Voice, 27(5), 556-566. doi:10.1016/j.jvoice.2012.11.008

Gelfer, M.P., & Mikos, V.A. (2005). The relative contributions of speaking fundamental frequency and formant frequencies to gender identification based on isolated vowels. Journal of Voice, 19(4), 544-554. doi: 10.1016/j/jvoice.2004.10.006

Gelfer, M. P., & Schofield, K. J. (2000). Comparison of acoustic and perceptual measures of voice in male-to-female transsexuals perceived as female versus those perceived as male. Journal of Voice, 14(1), 22-33. doi:10.1016/S0892-1997(00)80092-2

Hillenbrand, J. M., & Clark, M. J. (2009). The role of f(0) and formant frequencies in distinguishing the voices of men and women. Attention, Perception, & Psychophysics, 71(5), 1150-1166. doi:10.3758/APP.71.5.1150

King, R. S., Brown, G. R., & McCrea, C. R. (2011). Voice parameters that result in identification or misidentification of biological gender in male-to-female transgender veterans.International Journal of Transgenderism,13(3), 117-130. doi:10.1080/15532739.2011.664464

Mount, K. H., & Salmon, S. J. (1988). Changing the vocal characteristics of a postoperative transsexual patient: A longitudinal study. Journal of Communication Disorders, 21, 229-238.

Skuk, V. G. & Schweinberger, S. R. (2014). Influences of fundamental frequency, formant frequencies, aperiodicity, and spectrum level on the perception of voice gender. Journal of Speech, Language, and Hearing Research, 57, 285-296. doi: 10.1044/1092-4388(2013/12-0314)


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