In search of the perfect sound: The case of the Stradivarius violins

Milan, 6 May 2022 - What makes the sound of one violin preferable to that of another? Do some Stradivarius violins really have a special sound? To answer these questions, a multidisciplinary team coordinated by the CNR engaged 70 violin makers in a listening experiment to evaluate the sound qualities of four violins, including a Stradivarius. The results, published in The Journal of the Acoustical Society of America, suggest that what makes the Stradivarius the preferred sound is a particular balance in the properties of the violin's timbre.

Stradivarius violins are recognized around the world as an excellence in craftsmanship, a model for violin makers and the holy grail for collectors and musicians. However, several studies show that experienced violinists, when blindfolded, seem to prefer modern violins.

The experiment conceived by Carlo Andrea Rozzi from the CNR Nanoscience Institute (CNR-Nano), Alessandro Voltini from the ‘A. Stradivari’ Scuola internazional e di liuteria (International School of Violin Making) in Cremona, Fabio Antonacci from the Politecnico di Milano, Massimo Nucci and Massimo Grassi from the Department of General Psychology at the University of Padua (UniPadova), helps to clarify this apparent paradox. The researchers invited 70 violin makers from Cremona to analyse and compare the timbre of four violins - two modern, one factory and one Stradivarius - compared to the sound of a reference Stradivarius violin. Based solely on five notes, the listeners showed a marked preference for one particular violin, in this case the Stradivarius. The researchers then identified a kind of 'signature' that distinguishes the preferred violin sound from those considered less pleasant. “Thanks to an in-depth analysis of the descriptions provided by the listeners and vibro-acoustic measurements made on the instruments, we were able to describe the preferred sound as one that has a particular balance of 'openness', 'clarity' and 'nasality',” explains Carlo Andrea Rozzi from CNR-Nano, first author of the study.

“This is a double-blind listening experiment, i.e. conducted without the listeners and us researchers knowing which violin was playing while they were listening,” explains Massimo Grassi from UniPadova. “We used a very simple sound stimulus - the musical scale - so that the judgements were guided only by the timbre of the violin and not by other factors such as ‘liking/disliking’ a particular piece of music.”

“Establishing which aspects of the sound contribute to making the timbre of an instrument pleasant is important for violin making,” emphasises Fabio Antonacci from the Politecnico di Milano, “as it paves the way for the creation of instruments with desired timbral properties. The vibratory measurements made on these violins also have the purpose of building, in the future, a data repository that enables the relationship to be estimated between the way the instrument vibrates and the timbre.”

“The results suggest that not all instruments are created equal, regardless of whether they were built by Stradivari; but rather that we can find in the timbre of an instrument the qualities that make it better appreciated by listeners,” adds the CNR-Nano researcher.

The experiment was conducted in the name of excellence: thanks to the support of the Municipality of Cremona, the researchers had access to violins from the Historical collection of the Cremona Violin Museum and the excellent acoustics of the Auditorium room for listening tests. “The broad and committed participation of master violin makers and students from the International School of Violin Making provided us with very reliable data,” concludes Rozzi.