Long-term Acoustic Effects of Gender-Affirming Voice Training in Transgender Women.

OBJECTIVES: One role of a speech-language pathologist (SLP) is to help transgender clients in developing a healthy, gender-congruent communication. Transgender women frequently approach SLPs to train their voices to sound more feminine, however, long-term acoustic effects of the training needs to be rigorously examined in effectiveness studies. The aim of this study was to investigate the long-term effects (follow-up 1: 3months and follow-up 2: 1year after last session) of gender-affirming voice training for transgender women, in terms of acoustic parameters.

STUDY DESIGN: This study was a randomized sham-controlled trial with a cross-over design.

METHODS: Twenty-six transgender women were included for follow-up 1 and 18 for follow-up 2. All participants received 14weeks of gender-affirming voice training (4weeks sham training, 10weeks of voice feminization training: 5weeks pitch elevation training and 5weeks articulation-resonance training), but in a different order. Speech samples were recorded with Praat at four different time points (pre, post, follow-up 1, follow-up 2). Acoustic analysis included fo of sustained vowel /a:/, reading and spontaneous speech. Formant frequencies (F1 -F2 -F3 ) of vowels /a/, /i/, and /u/ were determined and vowel space was calculated. A linear mixed model was used to compare the acoustic voice measurements between measurements (pre - post, pre - follow-up 1, pre - follow-up 2, post - follow-up 1, post - follow-up 2, follow-up 1 - follow-up 2).

RESULTS: Most of the fo measurements and formant frequencies that increased immediately after the intervention, were stable at both follow-up measurements. The median fo during the sustained vowel, reading and spontaneous speech stayed increased at both follow-ups compared to the pre-measurement. However, a decrease of 16 Hz/1.7 ST (reading) and 12 Hz/1.5 ST (spontaneous speech) was detected between the post-measurement (169 Hz for reading, 144 Hz for spontaneous speech) and 1year after the last session (153 Hz and 132 Hz, respectively). The lower limit of fo did not change during reading and spontaneous speech, both directly after the intervention and during both follow-ups. F1-2 of vowel /a/ and the vowel space increased after the intervention and both follow-ups. Individual analyses showed that more aspects should be controlled after the intervention, such as exercises that were performed at home, or the duration of extra gender-affirming voice training sessions.

CONCLUSIONS: After 10 sessions of voice feminization training and follow-up measurements after 3months and 1year, stable increases were found for some formant frequencies and fo measurements, but not all of them. More time should be spent on increasing the fifth percentile of fo , as the lower limit of fo also contributes to the perception of more feminine voice.