Striking a chord

Fundamentals of physics found in the sound of music

By Steven Schultz

Princeton NJ -- It was the week after spring break and the freshman seminar had just finished a detailed discussion of the violin and the unique qualities of its sound. Freshmen Lauren Carpenter, a violinist, and Daniela Smolov, a pianist, came to the front of the room to play a moving duet from the opera "Orpheus and Eurydice" by the 18th-century composer Christoph Gluck. The class fell silent as the room filled with sound.

  
Students in the freshman seminar "Sound, Music and ... Physics" build on their common interest in music to learn physical principles that are important to many areas of natural science. Here, physics professor Pierre Piroué shows Lauren Carpenter (with violin) and Daniela Smolov how to use a computer to record and analyze sound waves from the violin.
 
  
The final notes faded away and the class, mostly musicians, burst into applause.

It may have seemed like an introductory music class, but the room was on the fourth floor of the Jadwin physics building. On the blackboard behind Carpenter were mathematical expressions of Newton's laws. Smolov was playing an electronic keyboard that sat -- surrounded by a computer, cables and microphones -- on the plywood top of a gray metal lab cart.

The class is Freshman Seminar 110 "Sound, Music and ... Physics" taught by Pierre Piroué, the Henry DeWolf Smyth Professor of Physics Emeritus.

Piroué created the class this year to harness students' natural interest in music as a vehicle for introducing them to physics. His goal is to draw students who may not naturally be inclined toward the sciences into the wonders of the physical laws that govern everything from the character of arpeggios to the birth of stars.

"The approach is to teach physics, but to start with music," said Piroué. "When you start with music, you have a common background. You never ask somebody, 'Do you like music?' You ask, 'What kind of music do you like?'"

So far, it seems the idea is working. In its first year, the course was immediately oversubscribed.

"He really balances the physics and the music. There is a real appreciation of the music," said freshman Ben Gerut, who plays the piano and guitar. "To have a class that's explaining your instrument to you is really great."

Samantha Adamson, who plays piano, said the class has begun to bring clarity to many of the ideas that she only vaguely knew were underlying the music she studied. "It made sense, but now it really makes sense," she said.

Students said that the course's lab activities, such as seeing the inside of a dismantled piano and measuring the tension on the strings, have exposed the vast complexity of music, but also made those ideas seem more accessible. "This class, and just the way the material is presented, makes it a lot more attainable," Adamson said.

Measured tones

Piroué's idea for the class began to take shape when he retired in 2001 after more than 40 years as a leading particle physicist. Not content with slowing down, he was intrigued when Daniel Marlow, chair of the physics department, suggested that he develop a freshman seminar. They kicked around a couple ideas, and Marlow suggested the physics of music as a topic.

"It clicked for me, because, as everyone knows here in the department, I am interested in music," Piroué said. He studied piano until he was 18 and picked it up again about 10 years ago. Since then he has played many times in an annual recital for musicians associated with the physics department.

Still, said Piroué, the idea was somewhat vague; he needed a sense of purpose, a specific approach. He read many books on the subject and finally found one that described a philosophy that made a lot of sense to him.

In "Measured Tones: The Interplay of Physics and Music," author Ian Johnston lays out an approach that essentially became Piroué's course description. The traditional way to teach the physics of music, Johnston argued, is to start with the key physical concepts of vibrations, waves and harmonic analysis and then apply the ideas to music and musical instruments. The trouble is that, unless the students have a natural affinity for the science, they quickly lose their grasp of the concepts and feel lost by the time they have a chance to apply them.

The alternative, said Piroué, is to start with the musical applications and bring in the physical concepts as they are needed.

"I was intrigued by that, and I thought it was absolutely right," said Piroué. "From my experience, it's very difficult to teach physics to people who are not naturally scientifically minded. They see things differently."

Piroué also realized that the course could go far beyond the physics of music. It could become a platform for helping students become comfortable with concepts that are used throughout the physical sciences and for countering declining science literacy. The physics that make an A played on a violin sound different from an A played on a piano are in some ways the same as the physics that allow scientists to discern a hydrogen atom from a helium atom. Just as each instrument has a characteristic signature in its sound waves, each element has a signature in the light it emits or reflects.

  
   Mark Daly (left) and Ayan Chatterjee measure the length of piano strings as part of a lab project to understand the string tension and other physical properties of piano design.
 
This analysis of waves, whether sound or light, is called spectroscopy and is one of the most fundamental of all scientific techniques. "Most of what we know about the universe is due to electromagnetic waves and what we get when we study the spectra from galaxies and stars," said Piroué.

In the class, Piroué, who is a native of Switzerland and speaks English with a crisp French accent, clearly relishes the material. "It's an incredible story, the story of the violin," he told the students. The instrument was invented in 1580 and, within a few decades, had been refined to the shape and structure it still has today, he said. Almost immediately, it became the reigning instrument.

"It's because of its wonderful sustaining, singing tone and its wide dynamic range," Piroué said, as he asked Carpenter to show off a few notes as examples.

"It gave the artist an opportunity to express himself in an incredible way," Piroué continued. "And in the same way that musicians rank the violin at the top of all instruments, so do physicists. It's so subtle, so complicated." With that, Piroué moved into a discussion of force and friction and how the bow and string and violin body interact to give the instrument its unique sound.

Friendly atmosphere

Piroué teaches the seminar once a week, dividing the three-hour session into half classroom and half lab work. Classes cover such topics as the relation between string tension and frequency, the history and physics of the piano, the acoustics of architecture and the working of the human ear.

Setting up the lab component was one of the biggest challenges in preparing the class, Piroué said. He became a regular customer at a local music store, obtaining keyboards, patch cords and many other musical items that are not regularly stocked in the Jadwin laboratories. "Students always complain about physics lab," he said. "It was important to give it a friendly atmosphere."

"The labs are great," said Gerut. "My friends don't believe me when I say I get to come into the lab and play music and mess around with keyboards."

For many students, that chance to explore makes the class an ideal opportunity.

"It just seemed like the perfect class for me in many ways," said Tali Malott, who stopped playing piano and flute when she came to Princeton and sees the class as a chance to reconnect with music and "answer a lot of questions I've always had in the back of my mind about music."

"I always wondered why playing certain tones together sounds so good," she said. "It's just one of those things I've wondered about -- how music works, how sound works. It's so interesting to see that a lot of that can be attributed to physical properties."

 
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April 14, 2003
Vol. 92, No. 23
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Contents

Page one
Fundamentals of physics found in the sound of music
Paul Muldoon honored with Pulitzer Prize for poetry

Inside
Library, research center launch arts and cultural policy data archive
Wild ape population undergoing 'catastrophic' decline
Booming Indian cinema plays starring role in Sachs scholar's research

People
Mathematician spins novel tale of life on a college campus
Spotlight
Briefs

Sections
Calendar of events
Nassau Notes
By the numbers:


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