Human vocal cords can vibrate more than 150 times per second, potentially racking up a million vibrations in just over an hour of speaking and damaging the membranes involved. And new research shows teachers spend nearly a fourth of their time at work talking—not including the silent pauses between words. “Professional voice users make up about a quarter of the U.S. population,” said Eric Hunter, an acoustician with the National Center for Voice and Speech at the Denver Center for the Performing Arts. “That includes singers and telemarketers, but one of the biggest chunks is teachers.” And voice loss shouldn’t be taken lightly. “About 40 percent of teachers report losing their voice sometime during their career,” he said, a dilemma costing taxpayers $2.5 billion each year in substitute teacher wages, sick pay and other expenses. The results of Hunter and his colleagues’ study are detailed in a recent issue of the Journal of the Acoustical Society of America, but he told LiveScience they need more data to fully assess the problem. “We have a sister project looking at the biological aspects,” Hunter said. “For example, the vibrating action of the vocal cords actually damages their edges, like a flag that flaps in the wind and begins to shred itself.” But until that information comes in, Hunter and his team are focused on getting more teachers to volunteer their voices—they currently have data from 31 subjects, but want to get to a total of 100 teachers. To find out just how chatty a teacher is, Hunter said study subjects receive a pocket PC hooked to a device called an accelerometer. “It’s not a microphone because it measures the movement of the skin, not sound waves,” he said. “It feeds data to the PC and tells us how long you speak down to the millisecond, plus at what pitch you spoke.” And every hour or so, the teachers run through a quick test that measures the strain of their voice. The acousticians also measured how often the teachers used their voice when not at work. “Off the clock, teachers speak only 14 percent of the time” and performed better on voice strain evaluations, Hunter said. While the research team was reluctant to provide ways for teachers to save their voices, Hunter did recommend engaging in more dialogue-like situations. Why? “We’re finding short breaks in blocks of speaking give the vocal cords time to recover,” he said. “It may have something to do with blood flow being interrupted vibration—that break gives the body to swoop in and heal, let the vocal cords recover.” As to whether male or female teachers are the most talkative: “Right now it looks like females,” Hunter said. What’s worse, he explained, is that female vocal cords vibrate faster than men’s to achieve a higher pitch. “For the same amount of speaking, their vocal cords tire more quickly.”
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