Voice gender diversity: expression, perception and acoustics.

The voice is a key marker of gender identity, yet gender non-conforming speakers often diverge from binary vocal norms. This review synthesizes findings from 45 studies published between January 2020 and January 2025 examining how gender is expressed and perceived for the voices of gender-diverse individuals. We report how gender identities and expressions are measured, how gender-diverse voices are perceived, and how acoustic features relate to both self-reported and perceived gender. While binary frameworks still influence the experimental methods used, a shift towards more inclusive models is emerging. Gender-diverse voices are frequently externally perceived or acoustically represented as falling between binary categories or as misaligned with affirmed gender identity. Similar to binary voice gender, fundamental frequency and formants are key components of expressed and perceived gender. However, these findings may be biased owing to the binary understanding of gender in the methods used, a general focus on transfeminine voices, and few investigations on the impact of listeners' identity. A few studies reported that gender non-conforming listeners tend to have a distinct understanding of voice gender compared with cisgender listeners. To move forward, future research should adopt inclusive perceptual tasks, account for listener demographics, and further explore self-perception of voice gender.