Loyola University Maryland

Emerging Scholars

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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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.  This has highlighted the need for speech-language pathologists to gain a concrete understanding of the dynamics of MTF transgender speech and voice.  It has been widely accepted that the most salient goal in achieving feminine voice is increasing pitch (fundamental frequency, or F0) to a female range of 170 Hz to 220 Hz (Hillenbrand & Clark, 2009).  However, existing consensus suggests that vowel formant frequencies need to be increased as well as pitch in order to give the perception of feminine voice. 

Currently, there is a lack of conclusive evidence regarding the relationship between fundamental frequency and vowel formant frequencies.  In addition, the efficacy of speech therapy in raising vowel formant frequencies has not been proven.  Thus, this study focuses on the relationship between increased pitch and vowel formant frequencies in transgender MTF speakers receiving speech therapy.  The purpose of this study is twofold and investigates the following:

1)      Do vowel formant frequencies F1-F3 in MTF transgender speakers change when fundamental frequency (F0, or pitch) increases to a feminine range?

2)      Can vowel formant frequencies F1-F3 in MTF transgender speakers be changed by purposefully adjusting articulator placement during vowel production?

This single subject study utilizing AB design has been approved by the Loyola IRB and Research Committee.  There are currently three participants enrolled in the study, all of whom are MTF transgender clients receiving voice therapy at the Loyola University Maryland Clinical Center in Columbia, MD.  Participants attend weekly therapy sessions targeting increased pitch and, subsequently, articulator adjustment to raise vowel formant frequencies.  The investigator first instructed each participant to read 12 syllables following the format of /h/+ /vowel/+ /d/ (ex. “heed”, “hid”, “head”) for purposes of obtaining baseline values for fundamental frequency (F0), and the first three vowel formants (F1, F2, F3).  Three trials of baseline values with the participant using their biological voice were recorded and measured to determine formant stability.  Once vowel formant stability and the relationship between increased F0 and F1-F3 were established, vowel formant therapy begins.  Because F1 is correlated with tongue height, and this would be significantly difficult to change, therapy does not focus on adjusting F1.  To increase F2, participants are taught to speak with increased tongue forward carriage. To increase F3, participants are taught to speak with increased lip spreading.  Each participant’s data is analyzed through PRAAT, plotted and inspected. Related samples t tests will be conducted to determine whether (vowel formant frequencies F1-F3 in MTF transgender speakers change when fundamental frequency (F0, or pitch) increases to a feminine range).  The F0, F1, F2, F3 values for each vowel will be analyzed and a Repeated Measures ANOVA will determine the differences between the 3 conditions: 1) pre-therapy biological male voice, 2) pre-therapy feminine voice, 3) post-therapy feminine voice with changed tongue/lip postures.


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