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

Abstract

ObjectivesOne 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: 3 months and follow-up 2: 1 year after last session) of gender-affirming voice training for transgender women, in terms of acoustic parameters. Study designThis study was a randomized sham-controlled trial with a cross-over design. Methods26 transgender women were included for follow-up 1 and 18 for follow-up 2. All participants received 14 weeks of gender-affirming voice training (4 weeks sham training, 10 weeks of voice feminization training: 5 weeks pitch elevation training (PET) and 5 weeks articulation-resonance training (ART)), but in a different order. Speech samples were recorded with Praat at 4 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). ResultsMost 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 one year 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. ConclusionsAfter ten sessions of voice feminization training and follow-up measurements after three months and one year, 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.