Wednesday, May 10, 1995

      Science and Technology

      If you're no Pavarotti (who is?), here's why

      The voice is an instrument that must be learned. If yours is a plastic ukulele, stick to the shower.

      by Shankar Vedantam
      The Philadelphia Inquirer

      Show time.

      Step into the shower and gracefully draw the curtain. Do you feel that welling up in the heart as the theater bursts into applause?

      As you reach for the soap, you draw in a mighty breath and reach for that high, high note--the kind of stratospheric note that lifts and liberates the soul.

      And then your voice, that graceful, beautiful thing, changes into something between a choke and a scream. Suddenly, the bathroom walls seem very thin.

      When it comes to singing, we're all limited by physics. Voices are sound-producing instruments. And like all instruments, some are better than others. They can accomplish so much, and no more.

      Training or gift?
      A bit of both

      Physicists and musicians still debate whether training is what brings a voice to excellence or if great singing is a natural gift. But this much is certain--how good a singer you are does depend heavily on the quality of the acoustic system installed between your chest and your lips.

      "If Joe Smith has a two octave range and his girlfriend or wife says it's of good quality, he has a good voice instrument," said Ingo Titze, a physicist at the University of Iowa who studies speech science. He was explaining a rule-of-thumb method for people to test their singing potential.

      "If someone gives him a pitch, can he imitate it and hold it? Does he have control over the quality of the sound?" asked Titze, who is also a tenor.

      For enthusiasts who feel up to proving themselves to the trained ear, music schools are developing sophisticated tests, besides the age old audition, to gauge talent.

      Some teachers are using high technology sound spectrographs to evaluate the potential of students. The spectrograph gives a graphical display o f all the components in the student's voice.

      But while Titze agrees with those who believe that great singing implies loads of natural talent, he says the reverse is not necessarily true. Many people have great voices but are lousy singers.

      "It's like putting someone in front of a great piano like a Steinway," Titze said. "They still have to learn how to play."

      Human beings produce sound by expelling air against a valve in the throat called the larynx. The larynx has a couple of fleshy shelves called the vocal folds that hang into the circular airway of the windpipe. The vocal folds are controlled by muscles in the throat.

      During normal breathing, the chest muscles expand to suck in air and relax when breathing out, so that the lungs empty themselves like a full balloon with an open mouth. During singing or speaking, the chest muscles force the air out in a controlled manner--imagine pressing the balloon with one hand while adjusting the size of the balloon's mouth with the other.

      As the air rushes out through the windpipe, the throat muscles push the vocal folds into the airstream, which sends them into vibration, producing; sound.

      The muscles themselves don't make the folds vibrate. They just hold the folds in the airstream and stretch or relax them. The more the folds get stretched, the faster they vibrate and the higher the pitch of the sound. The looser they are held, the lower the pitch.

      Why doesn't any C sound like Pavarotti's?

      The limits of pitch and sound are set by the size, shape and symmetry of the vocal folds and the strength and control of the chest and voice muscles.

      "If you poke a singer between the ribs, you'll find that the muscles are rock hard," said Katherine Harris, professor of speech and hearing sciences at the City University of New York. 'Also the way the muscles work can be trained."

      Sounds are not produced in the throat alone. The cavern of the mouth can change shape rapidly, sculpting the vibrating air into different patterns - varying pitch and intensity.

      "But the discerning shower-singer will now ask plaintively. "how come my C note doesn't sound like Luciano Pavarotti's or Whitney Houston's?"

      Even assuming two people sing exactly the same note at exactly the same loudness, they will sound very different. That's because of the same reason that the C note on a piano sounds different from a C on a guitar.

      It's because of a property of sound called harmonics. When we sing a note or play it on an instrument, what comes out is really a complex combination of notes.

      The strongest one is the basic note you're playing, say C. But there are also several notes that are mathematical "relatives" of the C note that get produced. Which "harmonics" get produced and how strong they are depends on the acoustical properties of the musical instrument or the person's vocal system.

      Some of the harmonics have lower frequencies than the C note. Others are higher.

      The harmonics are produced all the time, with every note you sing and every word you speak. They are your voice's signature. Harmonics make it possible to recognize a friend who calls on the telephone and says,"Hi it's me."

      An ideal singing voice keeps its pitch and loudness independent from each other. The better the singer, the better the control over a wide range of pitch and intensity.

      Lowness and pitch also tend to get mixed up at the upper end of humans' singing register, when the vocal folds become very highly stressed.

      Good singers also have a "stable vibrato," an ability to run up and down the register without switching from mellifluous to guttural to screech. They maintain the quality of their sound throughout.

      Since voices tend to get unstable at either end of the register, good singers practice to expand the region in which they can sing comfortably, without losing control of the quality of the note.