Did you ever see that episode of Friends where Phoebe had a cold but loved it because she was singing with a "sexy" voice? It turns out a bad head cold isn't the only way to acquire a sexier voice than usual. Research indicates that women's voices become more alluring when they're at their peak of fertility.

Recordings were taken of women's voices at different times during their menstrual cycle. When replayed to both women and men, the recordings taken closest to ovulation were rated as more attractive. Researchers think that hormones may affect the voice box, creating a sexier voice. More work is needed to determine exactly how the voice is affected. But I think we all know why, don't we?

Check out AOL Body for more on women's sexual health. Guys, here's a link for you, too.