The science of American.

The sixth season of the popular television show American Idol is in full swing and the judging trio of Paula Abdul, Randy Jackson, and Simon Cowell have been busy separating the Idol hopefuls from the musically challenged.

Last summer, the popular talent show held auditions in seven cities around the U.S. Contestants sing a cappella, or without musical accompaniment, before panels of judges. Those who impress Paula, Randy, and Simon move on to Hollywood, where the judges whittle down the field even further.

Once a few dozen semifinalists remain, the democratic part of the TV show kicks in. This season, the audience will start voting for its favorite crooners on February 21.

The winner of this season's contest is anyone's guess. But one thing is for sure: Without science, American Idol would fall flat. Science World talked to voice experts and tech wizards to discover what separates good singers from bad ones, and how the show's voting technology works.

PERFORMANCE

The contestant picks up the mike and gets ready to wow the crowd. What makes the singing voice sound sweet--and not screechy?

Singer

When Idol contestants open their mouths to sing, the audience hears the sounds produced by air moving through the singer's voice box, or larynx. The larynx is a group of muscles, bone, and a rubbery tissue called cartilage that's located in the throat. Vocal chords stretch across the larynx. When air from the lungs moves over these twin membrane-covered folds, their vibrations create sound.

Audience

Most Idol contestants don't get any further than singing for the judges in a nearly empty room in their audition city. But for the show's finale, two singers will test their voices in front of a packed house at the Kodak Theater in Los Angeles, California.

Whether the audience is large or small, a singer's sound waves hit the listener's ears in the same way: Sound waves are invisible waves of vibrating air molecules that travel from the singer's mouth to the audience's ears. Structures in the ear then translate these vibrations into signals that the brain recognizes as sound.

Judges

So what does a judge look for in a singer? Robert White, a voice professor at New York City's Juilliard School, says good singers have a mixture of talent and proper vocal technique. The best singers know how to fine-tune the sounds they produce by changing the shape of their mouth, lips, and tongue. They're also able to make their vocal chords vibrate at a specific frequency, or the number of waves that pass a point in a specific amount of time. The result: They hit a specific note. For instance, to sing an A on key means that a contestant's vocal chords must vibrate at 440 hertz (440 Hz). A singer's "range" is the highest and lowest vibrations that he or she can maintain.

VOTING

Get ready to punch the dial pad and vote for your favorite Idol contestant. What technologies help make your vote count?

Power Dialing

During the two-hour voting window, callers who get through can vote as many times as their redial buttons allow. But some overzealous Idol fans use specialized technology to cast thousands of votes--a violation of the show's rules.

When a rapid redialing device is connected to a landline phone, it can place roughly 1,200 calls per hour. When hooked up to a computer with a high-speed Internet connection, the device can generate thousands of calls simultaneously--as many as 125,000 calls an hour. The device was originally designed to redial phone numbers that are constantly busy.

But could "power dialing" unfairly influence voting results? The show's Web site says that power dialers' votes are disqualified if they are detected.

How can they spot power dialers? Sandy King, of Telescope Inc., the Los Angeles company that manages American Idol voting, told the magazine Broadcast and Cable that votes dialed at regular intervals indicate that the votes might have been machine-dialed.

Landline Phones

According to Broadcast and Cable, two of the nation's largest landline phone companies have reported huge spikes in call volumes on voting nights. Sometimes, callers are unable to get through to vote.

Why the busy signal? A landline telephone network is like a spider web, says Jason Hillery, a spokesperson for AT&T. When you make a phone call, the call goes to a central office in your town, which routes it to the number you dialed. If you're calling a faraway location, the central office redirects the call to a high-capacity system, called a backbone network, which carries the call across the country.

"Our backbone network is built to function even with extremely high call volumes," says Hillery. With landline phones, logjams usually occur at the local level. "When you pick up the phone and hear a dial tone, you're opening a circuit with the central office. Every central office has only a limited number of circuits," he says. For a show that averages more than 30 million viewers, it's easy for voters in some towns to overwhelm the central office.

Text Messaging

American Idol also allows viewers who are Cingular Wireless subscribers to vote by text messaging. Text messaging is the ability to send and receive short messages--usually no more than 160 characters--on a cellular phone. During the last season of American Idol, Cingular reported that more than 64.5 million show-related text messages were sent.

When casting a text message vote, the message is converted into digital signals (a series of on-off pulses), which are then transmitted via radio waves. The wireless carrier receives these signals instantly and then translates them back into characters. If the characters match a contestant's number, a vote is cast for that singer.

PRE-READING PRDMPTS

Jump-start your lesson with these pre-reading questions:

* More than 50,000 people tried out for the 2006 season of American Idol. But only one out of every 10,000 Americans has perfect pitch. That means they can identify the exact note being sung or played by a musical instrument just by hearing it. How do you think this ability could give singers a leg up on the competition?

* When singers audition for American Idol, they show off their vocal skills in front of the judges in a relatively empty audition room. If a contestant makes it onto the show, he or she will perform in a packed auditorium. The size and shape of a performance space affects how a singer sounds. That's because when the sound waves produced by the singer bounce off surfaces, a series of echoes called reverberations result. Different surfaces will cause the sound to reverberate at different intensities. How are sound waves produced? How do you perceive sound?

CRITICAL THINKING:

* After reading the article, have students discuss whether they think the current technology used for voting for their favorite American Idol contestant is fair. How could the voting methods be improved or changed to ensure that everyone can cast a fair vote?

CROSS-CURRICULAR CONNECTIONS:

HISTORY: Each week, American Idol chooses a different theme for the show, such as country music or love songs. Throughout history, humans have created many different styles of vocal music. Have each student select a different music style, and have him or her do research to create a time line showing when and how the vocal style originated and how it has evolved.

RESDURCES

* To learn more about what it takes to turn sounds into music, visit the Science of Music page at the Exploratorium's Web site: www.exploratorium.edu/music/index.html

* Read more about American Idol voting controversies in the magazine Broadcast & Cable at: www.broadcastingcable.com/article/CA417981.html?display=Top+of+the+Week

* This Scholastic Instructor Web site provides lesson plans to help discuss the science behind sound: http://content.scholastic.com/browse/article.jsp?id=3896

* For hands-on activities on sound waves, see TE 6 of the March 6, 2006, issue of Science World.