(Image: Edward J. Walsh, Boys Town National Research Hospital.)
Babies may look sweet and innocent, but their cries have just been compared to lion and tiger roars. The sounds are very similar, only babies "roar" at a much higher pitch.
The study, published in the latest PLoS ONE journal, helps to explain why it's hard to ignore all of these sounds, which appear universally to grate on the nerves of most mammals.
“Roaring is similar to what a baby sounds like when it cries,” speech scientist Ingo Titze, executive director of the National Center for Voice and Speech, was quoted as saying in a press release. “In some ways, the lion is a large replica of a crying baby, loud and noisy, but at a very low pitch.”
The finding also helps to explain how domesticated cats manipulate women with their vocalizations. All people are hardwired to respond to baby cries, but that's especially true for women. Crying house cats sound a lot like crying babies, causing us to react even when we may not consciously want to. (This has benefited cats for ages, revealing how they really are like babies to some owners, and I'm one of them.)
Both roars and cries are indeed meant to grab our attention. Titze said a baby “cries to have people come to help it. The lion uses similar attention-getting sound, but mainly to say, ‘I am here, this is my territory, get out of here.’”
He added, “In both cases, we hear loud, grating sounds that grab people’s ears. When a baby cries, the sound isn’t pretty. The sound is basically rough. The vibration isn’t regular.”
Titze and his team determined that big cats' loud and low-frequency roars, which also possess this irregular quality, are predetermined by physical properties of their vocal fold tissue. These tissues have the ability to stretch and shear. Previously it was suspected that nerve impulses from the brain helped to control the sounds.
For both human babies and cats, the vocal folds/cords are “very loose and gel-like” and vibrate irregularly to make roars sound rough, Titze said. The main difference is just that babies cry at a high-pitched frequency, while big cats have a low-frequency roar.
In terms of cats, the new study negates the idea that big felines sound the way they do because they have large vocal cords.
“We were trying to correct a previous assumption that lions and tigers roar at low fundamental frequencies because they have a huge vocal folds,” study co-author Tobias Riede, a research assistant professor of biology at the University of Utah and a research associate at the NCVS, was also quoted as saying in the press release.
“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 added. “We study a lot of animals –- deer, elk, dogs and cats. Lions and tigers are just interesting examples for very loud and low-frequency vocalization.”
Some other interesting findings from the new research:
“They roar with a sound that is frightening to people because it has this rough and raw quality,” Titze said. “Lions and tigers are deemed the kings of the beasts, partly because of their roars. Imagine if they sang beautiful tunes and they were very low-frequency tunes. Who’s going to be afraid of that?”