MANY a parent has suffered with the hope that more practice would improve the sounds produced by his or her child's merciless sawing of the youngster's first violin. Now researchers have found that regular practice not only improves the skills of violinists, but also the tone of the instrument.

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Researchers in England say that laboratory tests conducted on wood commonly used to make violins supports age-old claims by musicians that the regular playing of a stringed instrument improves its tone.

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Dr. David G. Hunt of the School of Engineering Systems and Design at South Bank University in London says his studies with pieces of spruce show that continuous forced vibrations similar to those experienced with regular use of a musical instrument changes the nature of the wood.

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In a letter published in the current issue of the journal Nature, Dr. Hunt and a graduate student, Emmanuel Balsan, said that wood vibrated in conditions of high humidity increased in stiffness and saw a decrease in dampening coefficient, a measure of cycles of vibrations emanating from the material. Both factors are known to help provide more pleasant tones in spruce, mature pine and other woods used in instrument sounding boards, experts say.

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Dr. Hunt, who studies the structure of wood for the construction industry, said the results concerning musical instruments were a byproduct of research into the effect of moisture in wood. A music lover and avid concertgoer, he said he built a guitar several years ago but was not a violin expert.

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"People don't understand entirely the structure of wood, even after using it and studying it for centuries," he said in a telephone interview, "Part of the strength of wood is based on the amount of water in it and the way it bonds."

The researchers vibrated beams of spruce at 10 cycles a second for 48 hours and the damping coefficient went down by 5 percent. The changes persisted when the vibrations stopped, they said. Lower damping coefficents mean that a single note is heard longer, which is considered a beneficial attribute.

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When the wood was vibrated in a chamber where the humidity was taken up to 80 to 90 percent, the damping coefficient went up fast before drifting downward, they reported. This resulted in a decrease in damping and increase in stiffness during vibrations that persisted when the vibrations were turned off, they said.

 

Dr. Hunt attributed the changes in the wood to a redistribution of moisture in the wood caused by the vibration that remained stable for several days after the test. Over time, perhaps months, he speculated, the wood was expected to go back to its initial state of equilibrium unless the vibrations were applied periodically.

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"Musicians have said that the sound of an instrument gets better the more you play it, and we have found a basis for that," he said.

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"Although for the best care of a musical instrument, both high and low humidities should be avoided," the researchers wrote, "the results suggest that at intermediate or high humidities, the sound quality may be improved by regular playing."

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Carleen Maley Hutchins of Montclair, N.J., considered one of the world's best violin makers and researchers, said she found the British work interesting and consistent with much of her research. Among other things, she has vibrated violins for 1,600 hours using frequencies from radio broadcasts and found that this changes wood resonance.

"This would appear to complement work I have been doing," Mrs. Hutchins said in a telephone interview, "but I would question their conclusion that moisture bonding is the reason. There is research to indicate that the molecular bonds of wood actually break because of vibration and that this is what affects the tonal qualities. So I think there may be more to it than moisture bonding."