Sound chemistry

For most of us, sound chemistry or sonochemistry is about the use of ultrasound in chemistry. The science has been around for about 80 years and now mainly focuses on the effect of ultrasound on reactions. Many reactions which are sluggish, or indeed can not proceed at all, can be mediated by bathing the reaction in ultrasonic waves.

Dr Muthupandian Ashokkumar, a senior lecturer at the University of Melbourne, is Australia's foremost expert on sonochemistry, with about 100 journal publications in the area of sonochemistry and sonoluminescence.

Dr Ashokkumar's current research focuses on developing new applications of ultrasound-induced chemical and physical effects in the food science area, in particular the sonochemical modification of the functionalities of food ingredients in order to enhance their bioactivities.

In a completely different take on sound chemistry - researchers at Texas A&M have proved that the chemicals used to treat the wood used in Stradivarius and Guarneri violins are the reasons for the distinct sound produced by the world-famous instruments.

The conclusions, published in the current issue of Nature magazine, have confirmed 30 years of work into the subject by Joseph Nagyvary, professor emeritus of biochemistry at Texas A&M University, who was the first to theorise that chemicals - not necessarily the wood - created the unique sound of the two violins. Nagyvary teamed with collaborators Joseph DiVerdi of Colorado State University and Noel Owen of Brigham Young University on the project.

"This research proves unquestionably that the wood of the great masters was subjected to an aggressive chemical treatment and the chemicals - most likely some sort of oxidising agents - had a crucial role in creating the great sound of the Stradivarius and the Guarneri," Nagyvary says.

"Like many discoveries, this one could have been accidental. Perhaps the violin makers were not even aware of the acoustical effects of the chemicals. Both Stradivari and Guarneri wanted to treat their violins to prevent worms from eating away the wood. They used some chemical agents to protect the wood from worm infestations of the time, and the unintended consequence from these chemicals was a sound like none other," he adds.

The team tested several instruments, including violins and cellos, produced by Stradivari and Guarneri from 1717 to around 1741, using spectra analysis and other methods.

The results and those previously reported by Nagyvary showed that two specific areas of the instruments accounted for their unique sound - chemicals used in the varnish and fillers of the instruments, and the overall wood treatment process used by Stradivari and Guarneri.

There is still a missing piece of the puzzle, Nagyvary believes.

"The next step is to identify the chemical agents involved. To do that, more precious wood samples are needed," he adds.

"But in the past, there has been a lack of cooperation from the antique violin business, and that has to be overcome. It may help us to produce violins and other instruments one day that are just as good as the million-dollar Stradivarius. And this research could also tell us ways to better preserve instruments, too."