In the following audio clips, recorded by University of Colorado Boulder researcher Lal Zimman, two transgender men say the same sentence. Both speakers’ voices have a mean pitch of 140 hertz, which is typically considered to be part of the male-sounding vocal range. But the two speakers pronounce “s” sounds differently, affecting whether their voices are perceived as male or female by the listener. In the first audio clip, a speaker called “Joe” uses low-frequency “s” sounds, and in the second clip, “Kam” uses high-frequency “s” sounds. When the clips were played for a group of 10 listeners participating in Zimman’s study, the group unanimously perceived “Joe” to be male and “Kam” to be female. Read the full news release for more details on Zimman’s work.