Why Stradivarius violins sound so good

Scientists have used a CT scanner and a modified version of a computer programme written to diagnose the chest disease emphysema to solve the mystery of why 300 year old Stradivarius and Guaneri violins sound so good.

Writing in the journal PLoS ONE, Leiden Univesity researcher Berend Stoel and Arkansas-based violin maker Terry Borman scanned 5 "classical" Stradivarius and Guaneri violins dating from 1715-1734, and 7 contemporary instruments.  In order to understand how the wood might be contributing to the way a violin sounds they fed the scan results into a modified version of a computer programme used normally to calculate the lung densities of patients with emphysema!

The results showed intriguing differences in the wood structure between the two groups of instruments.  Trees lay down annual growth rings corresponding to the production of new wood.  In general, growth in the spring tends to be faster, softer and more porous so the resulting wood is therefore less dense than growth occurring later in the season.

But the CT scans showed that the classical instruments showed much less variation (or differential) in density between the early and late growth than modern instruments.  Differentials in wood density will affect how well a piece of wood will vibrate and therefore the ultimate quality of the sound it can produce.  Having more homogenous wood could therefore be the key to a much purer sound.

However, scientists still don't know why the classical wood shows this dramatic reduction in density.  One possibility is that the weather in the 1700s, when there was a mini ice-age coinciding with a period of reduced solar activity called the Maunder mimimum, may have slowed tree growth leading to denser wood.  More likely, however, is that the ancient craftsmen knew a chemical trick or two to alter the structure of the woods to get just the sound they were after.

"It's possible that you could use this CT technique to select different types of wood that would be more like the wood that Stradivarius used. But if you are a lousy violin maker and use the best wood, you will still end up with a very bad violin," says Stoel.