LOS ANGELES, Nov. 1 (Xinhua) -- There is mounting evidence that when women are fertile, their voices in some conditions go up in pitch, according to a new study.

    The finding showed that female humans exhibit detectable clues when they are fertile, a condition formerly thought to be undetectable without medical evaluation, said the study conducted by researchers at the University of California in Los Angeles (UCLA).

    The researchers measured the pitch of 69 women through their ovulation cycles, and discovered that their voices in some conditions go up in pitch when they are fertile.

    The scientists said the study was based on the theory that humans find a higher pitch more attractive and more feminine.

    The changing voice joins what the researchers called a "suite of behaviors that women engage in during high fertility" that includes changes in the way they walk, and the mates that they choose when ovulating.

    The scientists theorize that women unconsciously change their voice in relation to fertility, and possibly only in social communication contexts.

    The finding was published in the Nov. issue of scientific journal Biology Letters.