Scientists have identified the design features that boost the acoustic power of violins.
Italian workshops of master violin-making families (such as Stradivari) produced increasingly powerful instruments in the renaissance and baroque musical eras during the 17th and 18th centuries, the so-called Cremonese era.
Advances in the manufacturing of violins happened mostly by accident rather than design, according to a new study by modern acousticians and fluid dynamicists at MIT.
Boffins teamed up with violinmakers at the North Bennet Street School in Boston in the US to analyse measurements from hundreds of Cremonese-era violins, identifying key design features that contribute to these particular violins’ acoustic power, or fullness of sound.
The team obtained technical drawings of Cremonese-era violins from museums, collector databases, and books, as well as X-ray and CAT scans of actual instruments. Dimensions of various features from one instrument to another, as well as measurements of acoustic resonances across instruments, were compared.
The key to a Stradivarius violin’s sound turns out to revolve around its holes or more precisely “the shape and length of its ‘f-holes’, the f-shaped openings through which air escapes”, as a statement on the researchers work explains.
The more elongated these are, the more sound a violin can produce. What’s more, an elongated sound hole takes up little space on the violin, while still producing a full sound – a design that the researchers found to be more power-efficient than the rounder sound holes of the violin’s ancestors, such as medieval fiddles, lyres, and rebecs.
The thickness of a violin’s back plate also contributes to its acoustic power. Violins carved from wood are relatively elastic: As the instrument produces sound, the violin’s body may respond to the air vibrations, contracting and expanding minutely. A thicker back plate, they found, would boost a violin’s sound.
Violins slowly evolved to more elongated f-holes and thicker back plates because of these improved acoustic features. To find out if design changes were intentional the researchers fed the measurements from hundreds of Cremonese-era violins into an evolutionary model, finding that any change in design could reasonably be explained by natural mutation – or, in this case, craftsmanship error.
Makers may have crafted violins with longer sound holes and thicker back plates not by design, but by accident, the researchers concluded.
“We found that if you try to replicate a sound hole exactly from the last one you made, you’ll always have a little error,” explained Nicholas Makris, a professor of mechanical and ocean engineering at MIT.
“You’re cutting with a knife into thin wood and you can’t get it perfectly, and the error we report is about 2 per cent … always within what would have happened if it was an evolutionary change, accidentally from random fluctuations.”
Although each violin maker inarguably possessed a good ear – in order to recognise and replicate the violins that sounded best – whether or not they recognised the particular design elements that contribute to a more powerful sound is still up for debate.
In other words, the violinmakers knew what was a better instrument to replicate but they didn’t necessarily know that its slender holes were what made the sound it produced tonally pleasing.
The scientists published their study, funded in part by the Office of Naval Research, in the Proceedings of the Royal Society.
Makris got tuned into the field of research after taking up the lute. The lute, which effectively became extinct for centuries before its recent re-emergence, is much quieter than the violin. Its sound holes are circular rather than f-shaped and featuring elaborate interior carvings known as rosettes.
Answering a musician’s simple question about whether or not carvings within a lute’s sound hole make a difference to the overall sound produced morphed over time into a seven-year project examining the acoustic dynamics of stringed instruments through time. ®