string theory guitar physics
July 25, 2014

Research Rock-Star: Oxford Scientist Analyses The Physics Of Playing Guitar

redOrbit Staff & Wire Reports - Your Universe Online

When most scientists discuss string theory, they aren’t referring to the physics behind the distinctive lead guitar techniques of Eric Clapton or Jimi Hendrix, but that’s exactly what one Oxford University researcher examines in a new PLOS ONE study.

“Very good guitarists will manipulate the strings to make the instrument sing,” Dr. David Robert Grimes, a postdoctoral researcher in Oxford University's Department of Oncology as well as a guitarist himself, said in a statement Thursday.

“On a piano, you've got the 12 chromatic notes in a scale,” he added. “On a guitar, you can bend the strings to get the notes in between. I wanted to understand what it was about these guitar techniques” – which include string-bending, tapping, vibrator and whammy bars – “that allows you to manipulate pitch.”

Typically, Dr. Grimes is working to develop mathematical models of oxygen distribution in an attempt to improve radiotherapy treatments for cancer patients. However, he has also been a session musician and a member of a Dublin band in the past, and the university describes him as “a keen guitarist.”

Working in his spare time, first at Dublin City University and now at Oxford, Dr. Grimes has been studying on the physics behind the guitar-playing techniques of the greats. He worked out equations to describe how string bending, vibrato and whammy bars change the pitch of a note, as well as how a string’s thickness and its ability to stretch under force (the Young's modulus) can have a tremendous impact on the change in pitch.

He also figured out how easy it is to perform hammer-ons and pull-offs, depending on how high the guitar strings are above the finger board. In his experiments, Dr. Grimes confirmed an equation for string bends by measuring the frequency of the sound produced for strings bent through different angles on a guitar, the university explained.

“I took one of my oldest guitars down to the engineering lab at Dublin City University to one of the people I knew there and explained that I wanted to strip it down to do this experiment,” he said. “We had to accurately bend the strings to different extents and measure the frequency produced. He was a musician too and looked at me with abject horror. But we both knew it needed to be done – We put some nails into my guitar for science.”

While scientists have long understood the physics of vibrating strings and string instruments, this is the first time that anyone has worked out how bending the string and other similar effects can alter the pitch of a sound. Likewise, no one had previously determined how this depends on the tension of the string or the amount of force applied.

“It turns out it's actually reasonably straightforward,” Dr. Grimes said. “It's an experiment a decent physics undergraduate could do, and a cool way of studying some basic physics principles. It's also potentially useful to string manufacturers and digital instrument modelers.”

And what rock gods helped inspire his love of the guitar and his interest in the physics behind the art form? “Dave Gilmour of Pink Floyd has the most amazing bend control. And Steve Vai is the kind of guy you hate for his sheer talent,” he said. “[But] I think the only person I ever wrote fan mail to was Brian May of Queen – he was one of the reasons I got into playing music. It's still one of my life's ambitions to have a conversation with Brian May.”