A recent study of creaky voice

Yuasa. (2010). Creaky voice: A new feminine voice quality for young urban oriented upwardly mobile American women? American Speech. 85(3): 315-337.

Yuasa conducts a two-part study of creak: an auditory and acoustic analysis of creaky voice in young speakers and a perception survey completed by college students about the social significance of women’s use of creak in natural conversation. The conversations average ten minutes in length and focus on the topic of food, what she sees to be a neutral topic (but is this actually neutral, and how is it "natural" to control for topic?)

Yuasa counts creaky voice at the word level, in a 401-word sample taken randomly from each recording. She locates creak auditorily and confirms her assessment using the program Praat to look at the waveforms and spectrograms of the words. For her statistical assessment of the data, Yuasa uses a t-test. She finds that the differences between the American female speakers and the American men (p = 0.0133) and the American female speakers and the Japanese female speakers (p = 0.0267) is significant; American women have a higher rate of use of creak.

The perception study includes 175 college students in both Northern California and Eastern Iowa who listened to and responded to questions about audio files online (one modal voice recording and one creaky voice recording from the same female speaker). Then they were asked 1.) if they heard the second type of voice (creak) a lot where they live and 2.) what traits the women in the recordings project just with their voice and 3) to rate the women's characteristics based on their voice quality with predetermined binary choices such as formal versus informal.

Many of the participants in the survey remarked that they often heard creak where they lived and that the voice type suggests the following attributes: hesitant, informal, non-aggressive, as well as educated, professional and urban. Yuasa suggests that young American women may be using creaky voice more to continue the trend of “lowering” their voices to reappropriate creak as portraying the contemporary, urban and upwardly-mobile woman.

While the above study is thought-provoking and Yuasa's analysis is intriguing, saying that creaky voice indexes numerous characteristics at once (based on survey questions that gave participants binary choices, perhaps forcing some responses) for American women in general is an ambitious claim that requires much more research, especially since the social meaning of creaky voice and women has only recently been a topic of study.