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Physicist explores the mysteries of great violins

What makes a Stradivarius sound like a Stradivarius?

Between about 1600 and 1750, the violin makers of Cremona, Italy, produced instruments whose "voices" were the most beautiful ever heard. Today, those 350-year-old violins remain regally unique. But physicist and violin maker Jack Fry believes their voices (and those of modern violins) can be analyzed with the mathematics of acoustics and then replicated or modified using the humblest of tools: sand paper and coat hangers.

Fry is professor emeritus of physics at the University of Madison at Wisconsin, where he established the Experimental High Energy Physics program in 1952. For the past 30 years, he has also explored the physics of stringed instrument construction. He spoke about his research on the violin's structural acoustics on April 19 in Killian Hall.

Rose Mary Harbison, a professional violinist and a longtime associate of Fry's, told the audience that violins produced in the so-called "golden age" have "personalities" of their own. "The violin can sound seductive, pleading, secretive or even nasty,"said Harbison, whose husband is composer and Institute Professor John Harbison. But there is no well-developed vocabulary to describe these sounds, which makes them difficult to analyze or reproduce.

Fry studies how a violin's proportions and construction contribute to its distinctive voice. By analyzing old instruments, he said, he has learned to modify modern violins to approximate the qualities of great instruments of the past.

Fry explained that a violin's voice is dependent on several aspects of its construction. These include the thickness of the fibers that run parallel to the "tweeter," an area between the outside of the violin's right F hole and the instrument's edge. That area affects the very high frequencies--important for both a violin's carrying power and the "silkiness" of its voice.

In contrast to his mathematics' subtlety, the tools Fry uses to modify his modern violins are low-tech: small scrapers made from bent coat hangers and tipped with sandpaper, which he uses to reach inside a violin and remove infinitesimal amounts of wood from the fibers. The quantity is so small that it wouldn't even be visible as dust, he said.

After the presentation, Fry and Harbison gave a demonstration of his method: Harbison played on a violin, then handed it over to Fry for scraping as the two discussed how to "smooth" its voice. After several repetitions, Harbison's eyes brightened at the sound. "Yes!" she said. She asked the audience, "Can you hear the difference?" They murmured assent. Sternly, she told Fry, "You can't have it back!" Fry smiled and put his scraper away.

A version of this article appeared in MIT Tech Talk on May 12, 2004 (download PDF).

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