![]() Measurements of vocal fold resistance to stretching and shearing let researchers accurately predict the "fundamental frequency" ranges at which lions and tigers are known to roar, and the lung pressures needed to produce those roars. We tested if the mechanical properties of the vocal folds allowed us to make predictions about the sound." Riede says the scientists "set out to find out the relationship between structure of the vocal folds and how they work to produce the roar in lions and tigers. "It's true they have large vocal folds, but the shape and the viscoelastic properties make the roars so loud and deep," he says. "We were trying to correct a previous assumption that lions and tigers roar at low fundamental frequencies because they have a huge vocal folds," says study co-author Tobias Riede, a research assistant professor of biology at the University of Utah and a research associate at the National Center for Voice and Speech. The fat also may cushion the vocal folds and provide repair material when they are damaged, the researchers say. Instead, the fat helps give the vocal folds their square shape where they protrude into the airway, unlike triangular vocal folds in most species. ![]() That contradicts a theory that lions roar deeply because the vocal folds are heavy with fat. The new study's key finding is that lions and tigers can roar loudly and deeply because their vocal folds have a flat, square shape and can withstand strong stretching and shearing. Roaring Frequency Dictated by Structure of Vocal Folds The main difference: Babies cry at a high-pitched frequency, while big cats have a low-frequency roar. The same is true of roars by lions and tigers, and, like babies, their vocal folds (commonly called vocal cords) are "very loose and gel-like" and vibrate irregularly to make roars sound rough, Titze says. When a baby cries, the sound isn't pretty. "In both cases, we hear loud, grating sounds that grab people's ears. The lion uses similar attention-getting sound, but mainly to say, 'I am here, this is my territory, get out of here.'" While the comparison was not part of the study, Titze says a baby "cries to have people come to help it. ![]() 2, in the Public Library of Science's online journal PLoS ONE. The study of lion and tiger vocal folds and how they produce roaring - vocalizations used by big cats to claim their territory - was set for publication on Nov. "In some ways, the lion is a large replica of a crying baby, loud and noisy, but at very low pitch." "Roaring is similar to what a baby sounds like when it cries," says speech scientist Ingo Titze, executive director of the National Center for Voice and Speech, which is administered by the University of Utah. So says the senior author of a new study that shows lions' and tigers' loud, low-frequency roars are predetermined by physical properties of their vocal fold tissue - namely, the ability to stretch and shear - and not by nerve impulses from the brain.
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