The findings are published in this month's Journal of the Acoustical Society of America. If humans had maintained a large vocal sac, our voices would be particularly prone to cracking, said Reide. Men's voices tend to fall within the 80 to 120 hertz spectrum, while women's voices fall between 180 to 250 hertz. "These numbers are identical to the frequency of vocal fold vibrations," he said, adding that air sacs would be a disadvantage since "our voices would break all of the time if the air sac resonance [would] come near the frequency of the vocal fold vibrations." Humans instead have what appear to be relics of the larger air sacs. These are the laryngeal ventricles, located in the voice box. Chuck Brown, a professor of psychology at the University of South Alabama who specializes in the biology of acoustic communication, told Discovery News that prior to the research, he did not know that other primates may use the air sac effect "to heighten the possibility of communication in some settings." "In speech, instabilities in voicing are usually regarded as undesirable phenomena that tend to impair communication," Brown said. "Yet, in many of our closest primate relatives, the presence of air sacs and other features of their vocal anatomy appear to be designed to expand the opportunities" for communication. Riede and his team have already confirmed their findings by studying how air sacs work in Siamang gibbons, but they hope to conduct more studies on animals with air sacs -- big and small -- in the future. Related Links: |
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