Alternating Masculinized and Feminized Vocal Motor Behavior: A self-study Single Case Experimental Design (SCED)

Researchers are becoming increasingly interested in the effectiveness of gender
affirming voice (and communication) training. To date, no study has assessed the
possibility of a person alternating between feminized and masculinized vocal motor
behavior, although this type of demand is growing among non-binary people, artists,
and binary trans people. The aim of this article is to determine whether an individual
can alternate between two vocal motor behaviors (VMBs), one feminized and the other
masculinized, without creating vocal dysfunctions. The assigned-male-at-birth
participant-researcher underwent 10 feminizing vocal training of 30 minutes each, one
per week, with another Speech and Language Therapist. Measures were taken in a
span of 23 weeks. Three research questions are addressed: (1) How can a feminized
VMB be acquired by the assigned-male-at-birth participant-researcher? (2) How does
the masculinized VMB change after acquisition of the feminized VMB? (3) How does
the feminized VMB change over time if it is not used permanently? The quantitative
prospective self-study Single-Case Experimental Design (SCED) was used to assess
the acoustic parameters related to fundamental frequency, formants, and prosody at
eight different times (four with a feminized voice and four with a masculinized voice),
whereas the self-study design allowed qualitative aspects and a proprioceptive
description of the VMBs. The masculinized VMB was not affected by the alternating
VMBs during the experiment. An upward trend from the first to the last measure times
in feminized VMB was observed for the resonance frequencies of the third and the
fourth formant (fR3 and fR4), as well as for the mean resonance frequency (fRM).
Significantly higher parameters were reported in feminized VMB for the length of the
vowels (Tvow), the resonance frequency of the fourth formant (fR4), pitch (fo) and its
variation in continuous speech (sd_fo) compared to masculinized VMB. The results
show that the participant-researcher was able to acquire a second VMB that was
different from the first. The voice of the participant-researcher kept being healthy. In
addition, the feminized VMB improved over time as shown by the upward trend
observe in some parameters.