Instead, the fat helps give the vocal folds their square shape where they protrude into the airway, unlike triangular vocal folds in most species. The fat also may cushion the vocal folds and provide repair material when they are damaged, the researchers say.
"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.
"It's true they have large vocal folds, but the shape and the viscoelastic properties [tension and shearing strength] make the roars so loud and deep," he says.
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. We tested if the mechanical properties of the vocal folds allowed us to make predictions about the sound."
They did. 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.
Titze and Riede conducted the research with first author Sarah Klemuk, an adjunct assistant professor of communication sciences at the University of Iowa; and Edward Walsh, director of auditory physiology at Boys Town National Research Hospital in Omaha, Neb. Titze is on the faculty at the University of Iowa and University of Utah, where he is a research professor of otolaryngology and medicinal chemistry. The research was funded by the National Institutes of Health and the National Science Foundation.
"We study a lot of animals deer, elk,
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University of Utah