Subtle vocal changes occur across the menstrual cycle in women who are not using hormonal contraception, according to a study published in PLOS One.

“As an evolutionary psychologist, generally interested in the hormonal regulation of mating behavior, I studied changes across the menstrual cycle. Interest in voice production came a bit later, after finishing a course in linguistics,” said study author Irena Pavela Banai of the University of Zadar.

“Combining these two fields resulted in the investigation of voice changes across the cycle, assuming that any vocal changes related to hormone fluctuation have an important function in mating behavior,” she continued. “Relatedly, it was really interesting to compare voices of naturally cycling women and users of exogenous hormones contained in monophasic pills (meaning they have stable hormonal profile throughout the entire cycle) and to inspect the influence of synthetic hormones, if any, on women’s voice.”

“I find this topic very important since more than a third of women in their reproductive age in western societies are using pills,” Banai said.

The researcher examined vocal changes across the menstrual cycle in 44 women who had not taken hormonal contraceptives and 21 women using monophasic hormonal contraceptives. She recorded the women speaking five vowels (/a/, /e/ , /i/, /o/ and /u/) in three different phases of the menstrual cycle.

Banai found that women who were not using hormonal contraceptives showed some changes in their voice across the menstrual cycle. In particular, they had lower minimum pitch in the late follicular phase compared to the menstrual phase, and they had lower voice intensity in the luteal phase.

There were no significant vocal changes across the menstrual cycle among the women using hormonal contraceptives.

“A takeaway message would be that women’s voices do change during the menstrual cycle, most likely due to fluctuations of sex hormones. Probably some women, like professional singers, notice that their ability to reach high notes, for example, is different in different cycle points, and these changes are normal,” Banai told PsyPost.

“However, pill usage may disrupt naturally occurring changes in voice production and make voice more stable throughout the cycle, or even less feminine to some extent.”

She also found that, overall, naturally cycling women showed a greater ability to produce higher pitched tones compared to contraception users.

A person’s voice can convey important information about them. However, the vocal changes found in the study were subtle. It is unclear if another person could detect them in everyday conversation.

“It is worth pointing out that voice in this study was analyzed during vowel production. So, based on these results it is not quite possible to conclude that similar voice changes would occur during real communication and during normal conversation,” Banai explained.

“It might not be possible to capture some vocal changes that would normally occur during free speech. In fact, my colleagues and I have already tested this assumption and conducted another experiment in which we recorded women’s voice during free speech in various cycle phases, and the results are promising, so we plan to investigate this further.”