Listeners’ Perception of Gender after Raising Vowel Formant Frequencies in a Male Speaker
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Current clinical practice in voice therapy for male-to-female (MtF) transgender clients focuses on raising modal frequency to a level that can be representative of either male or female, termed “gender neutral”. However, listening studies have revealed that raising pitch alone is not sufficient to change gender perception. One possible explanation is that the vowel formant frequencies (F1-F3) have remained in a male range. A few studies have confirmed that through therapy, MtF transgender clients can raise their vowel formant frequencies by altering tongue position and lip posture. However there is no consensus regarding which formant and at what frequency range listeners change their gender perception.
The purpose of this study was to identify which formant(s) F1-F3 and frequency level(s) are most influential in listeners’ perception of gender neutral or feminine voice, by systematically manipulating the formant frequencies from 1500ms vowel samples of a biological male voice. Using a customized Matlab program, vowel samples were manipulated by isolating each formant using a corresponding band pass filter designed with cutoff frequencies matching the specified frequency range, modifying the isolated formant, and then combining the modified and unmodified components of the sample. Individual and combined vowel formant frequencies F1–F3 were increased in 20% increments until the male vowel formants matched those typical of a female. Samples were randomized into a video format and played for listeners to perceptually categorize each sample as male, female, or gender neutral.
Results of this study will indicate the formant(s) and the frequency range(s) that are associated with a perceptual shift in gender identification. These results could have clinical implications in creating speech treatment goals for MtF transgendered individuals that will result in a more successful transition.