Washington, October 3 : Researchers at East Carolina University in Greenville, North Carolina, have identified a measurable sound quality that distinguishes the superior quality violins made by eighteenth-century Italian instrument-makers Stradivari and Guarneri del Gesu from cheap, factory-made instruments.
Research leader George Bissinger spent ten years painstakingly measuring the acoustics of violins rated from "bad" to "excellent" by professional musicians, and observed that the 'excellent' old Italian violins in his sample showed a significantly stronger acoustic response in the lower octaves than did the 'bad' violins.
The instruments rated merely "good" had intermediate values, the researcher said.
He revealed that the high-quality tone was caused by a single mode of vibration of air inside the body, which radiated sound strongly through the violin's f-holes.
Bissinger measured all manner of sound characteristics for the 17 instruments in his sample that included legendary instruments known as the 'Titian' and 'Willemotte' Stradivari and the 'Plowden' del Ges, made respectively in 1715, 1734 and 1735, to mass-produced instruments for beginners.
He focused on the properties of the key vibrational resonances or 'modes' of the instruments, recording the frequencies of these modes, the radiativity (the sound radiated for a certain applied force to the strings at the bridge), the degree of focusing in specific directions (directivity), the flexibility of the wooden body plates, and the amount of damping of the sound.
"The radiativity is closest to what the violinist hears and thus bears most directly on the quality perception," he says.
Almost all of these features showed no discernible trends from bad to good instruments, but the best violins showed a more even radiation of sound across the range of acoustic frequencies that they generated.
Bissinger believes that the greater strength of the best violins' lowest-octave response could partially account of the richness and sweetness of tone.
"They (violinists) generally like a big sound low down," he says.
Though Bissinger believes that a 'great' violin is created by a great violinist, his study suggests that the instruments themselves do matter.
The researcher says that even some 'bad' instruments can be made into 'good' ones by paying close attention to some basic details of construction and set-up.
"Even a 'bad' violin somehow contains the essence of good violin sound, needing only the proper driving force at the bridge to elicit its capabilities," he says.
"Violin-makers could actually use these results to help achieve a certain sound. There could be a much larger number of exceptional violins than there are," he adds.