Vocal Cords
The vocal cords (also called vocal folds) are made up of two bands of folded mucous membrane, which are stretched horizontally across the larynx (voice box). Although there are two sets of bands, only one is involved in actually producing sound. The vocal cords vibrate when pulled together and when air is passing up from the lungs, thus producing the vocal sounds we hear.
The vocal cords are white in color becausethere is little blood circulation in this region.
A person’s voice pitch is determined by the resonant frequency of their.
vocal cords. In an adult male, this average frequency is about 125 Hz. The voice pitch of an adult female is around 210 Hz, and that of children is about 300 Hz
Born to Roar: Lion’ and Tigers’ Fearsome Roars Are Due to Their Unusual Vocal Cords
When lions and tigers roar loudly and deeply – terrifying every creature within earshot – they are somewhat like human babies crying for attention, although their voices are much deeper.
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.
“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. “In some ways, the lion is a large replica of a crying baby, loud and noisy, but at very low pitch.”
Titze says 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.”
“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 vibrations isn’t regular.”
The same is true of roars by lions and tigers. and, like babies, their vocal folds (commonly called vocal cords) are “very loose and gel0like” and vibrate irregularly to make roars sound rough. The main difference: Babies cry at a high-pitched frequency, while big cats have a low-frequency roar.
In this new study, scientists had set out to answer the question, “why do lions and tigers sound the way they do when they roar?” Was it because their vocal cords were larger than other mammals? Or was it because of their shape? Mainly researches had speculated that their deep roars were caused by vocal folds heavily weighed down by a layer of fat.
“We study a lot of animals, deer, elk, dogs, and cats,” the scientist said. “lions and tigers are just interesting examples for very loud and low frequency vocalization.” In fact, a lion’s or tiger’s roar can reach 114 decibels to someone standing a few feet away, which is about 25 times as loud as a gas lawn mower. And roars aren’t delivered one at a time; instead, lions roar about 50 times in 90-second bout.
“They roar with a sound that is frightening to people because it has this rough and raw quality,” Titze says. “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.
These studies have a practical aspect. “If you understand how vocal folds are structured and what effects that structure has on vocal production, then it could help doctors make decisions on how to reconstruct damaged vocal fold tissue” in people such as cancer patients, singers, teachers, coaches and drill sergeants, he says.
Adapted from extracts taken from the Science Daily Website:http://www.sciencedaily.com/releases/2011/11/111102190012.htm?+Animals+News+–+Cats)