Good vibrations make violins sing

By Mick Hamer VIOLINISTS will tell you that they can produce a sweeter sound with a regularly played fiddle. Now engineers led by David Hunt of London’s South Bank University say they know why. The key to the sound of a stringed instrument is its body, which is often made of spruce. If the wood is not stiff enough the body will rapidly damp sounds, producing a dull tone. Hunt and his colleagues found that inducing vibrations of 10 hertz in a beam of spruce for 48 hours, simulating the effect of regular playing, could make the wood stiffer and reduce its tendency to damp sounds. They describe their results in this week’s issue of Nature. The effect depends on humidity. At 40 per cent humidity, the equivalent of a dry summer day, the vibrations made little difference to the stiffness of the wood. But at 90 per cent humidity the vibrations made the wood noticeably stiffer, reducing its damping effect by about 5 per cent. The engineers have yet to perform tests at intermediate humidities, but Hunt suspects the stiffening will occur unless the air is very dry. The human ear is very sensitive to these small changes, says Hunt. “Generally it sounds better if the sound lasts a little longer.” Most of the increase in stiffness occurs during the first 12 hours of induced vibration, and after 48 hours further vibration has no effect. The changes seem to be permanent, so once an instrument has been played its sound should stay sweet forever. The physical reasons for the change in stiffness are not known, but Hunt, whose day-to-day work is concerned with structural timber in buildings, says:
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