Violin makers, aka luthiers, traditionally learn from hands-on experience how to craft parts and select materials to shape an instrument’s final sound. MIT engineers hope to streamline that painstaking process with their new virtual violin. It’s a computer simulation tool that can capture the precise physics of the instrument and even reproduce a realistic sound of a plucked string, according to a paper published in the journal npj Acoustics.

Unlike the more common software programs and plugins that simulate violin sounds via sampling, averaging the final sound based on thousands of notes, the MIT model is based on the fundamental physics of the instrument. “We’re not saying that we can reproduce the artisan’s magic,” said co-author Nicholas Makris. “We’re just trying to understand the physics of violin sound, and perhaps help luthiers in the design process.”

Violin acoustics has long been a hot topic of research among acousticians, particularly when it comes to unlocking the secret to the superior sounds of violins crafted during the so-called “Golden Age”—notably the instruments of famed Cremona luthier Antonio Stradivari, as well as those of the Amati family and Giuseppe Guarneri. There are plenty of variables to consider, given a violin’s acoustic complexity.

Per my 2021 article, the (perceived) unique sound can’t just be due to the instrument’s geometry, although Stradivari’s geometrical approach gave us the violin’s signature shape. It might be due to the wood; some researchers have hypothesized that Stradivari used Alpine spruce grown during a period of uncommonly cold weather for the region. The annual growth rings were closer together, making the wood unusually dense. Differences in wood density, they argue, would have an impact on the instrument’s vibrational efficiency and hence its sound.

The construction of a violin.

Or perhaps it was the varnish Stradivari used: a cocktail of honey, egg whites, and gum arabic. A 2022 study involving nanoscale imaging of two such instruments revealed a protein-based layer at the interface of the wood and the varnish, which may influence the wood’s natural resonance.

Biochemist Joseph Nagyvary has argued that it was the chemicals used to treat the wood that give Stradivari violins their unique sound, specifically salts of copper, iron, and chromium used to preserve the wood—all of which are excellent wood preservers but may also have altered the instruments’ acoustical properties. A 2021 study supported that argument, identifying borax, zinc, copper, alum, and lime water as the most likely chemicals affecting the sound.

CT scans have provided quite a bit of insight into the conundrum, since the technique can reveal wood density, size and shapes, volume measurements, and thickness graduation, as well as any damage or repairs to a given instrument. For instance, a 2009 study used CT scans to study the material properties of the wood. In 2011, Minnesota radiologist Steven Sirr took detailed CT scans of the 1704 “Betts” violin and then collaborated with two luthiers to make a replica.

One of the most thorough investigations was the Strad3D project, spearheaded in 2006 by the late George Bissinger. That project used 3D scanning lasers to make detailed quantitative measurements of the acoustic properties of several Stradivarius violins, essentially mapping out precisely how the instruments vibrate and hence produce their distinctive sound. (For what it’s worth, when I interviewed Bissinger way back in 2007, he was skeptical of efforts to one day reproduce the sound quality of a Stradivarius violin on a mass scale, insisting that making an instrument is as much art as science and that there is no single secret to the Stradivari sound.)

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