Lung density software explores the Stradivarius violin
Using an adaptation of a computer program developed to calculate lung densities in people with emphysema, with a medical scanner, researchers have been able to analyse the physical properties of violins without risking damage to instruments worth millions of dollars. Their findings as to why a Stradivarius violin sounds so good is now attributed of the remarkably even density of their wood.
For the past 300 years, musicians and scientists have puzzled over the amazing and unparalleled quality of classical Cremonese violins made by the Italian masters Antonio Stradivari and Giuseppe Guarneri del Gesu.Now researchers, a Dutch doctor and a violin maker from Arkansas think they have the answer after comparing five classical and eight modern violins in a computed tomography (CT) scanner normally used to examine patients. They found no significant differences between the median densities of the modern and the antique violins, but the did discover far less variation between wood grains of early and late growth in the older ones.
Since wood density differentials affects vibration and thus sound quality, the discovery may well explain the 
superiority of the Cremonese violins, they reported in the online journal PLoS ONE .
The violins were scanned at Mount Sinai Hospital in New York City, USA, using a multi-detector row CT scanner (Sensation Cardiac 64, Siemens, Germany). The scans produced 3-dimensional data sets of approximately 1200×512×512 voxels for each violin.
A dedicated computer program was developed to automatically detect the superior and inferior surface of the top and back plates. From these surfaces, the local plate thickness, median wood density and density differential were calculated, as discussed below. Additionally, the volume of the sound box (luminal volume) was also calculated.
So why is the maple and spruce wood in a Stradivarius so different? According to the Stradivarius Organistion, "the spruce was used for the top and internal parts, while the maple was utilised for the back of the violin, the strip, and the neck. Minerals such as sodium, potassium silicate, Bianca, and potassium borate, were also utilised to enhance the quality of the wood."
Part of the reason may be that trees grow slightly differently today than in the past.
"Climate difference could explain part of it, but treatment of the wood could be another explanation. A third answer could simply be the ageing of the wood over the past 300 years. There is no way of knowing from this data; we've just shown that there are density differences."
Dr Berend Stoel of the Leiden University Medical Center told Reuters.
But Stoel and U.S. violin maker, Terry Borman think the research may help modern
instrument makers seeking to more closely
replicate the work of the Italian masters.
[Above] Regions of interest (ROI) Five different ROI's of 100×100 pixels were defined, carefully avoiding repair work. The same areas were taken from the top and back plates.
Source: http://uk.reuters.com
Research article: http://tinyurl.com/3l42x4