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The Art and the Science of Acoustics

Why does music sound fuller and richer in some concert halls than it does in others? Why does a minister’s sermon resonate clearly, even in the back row, of some churches and not in others?  Why is it easy to hear a teacher in some classrooms and not in others?

Physics professor David Bradley (left) and his URSI fellows Ian Kowolok ’16 and Ariana Sharma ’14 setting up their acoustics experiment / Photo by Buck Lewis

The answer to these questions can be summed up in a single word: acoustics. If you know how sound travels, how it bounces off the surfaces in the room before it strikes your eardrum, you can design a concert hall or a church or a classroom that makes it easier for everyone in that room to hear.

But how exactly do sound waves travel, and what happens when they hit a variety of surfaces along the way? Those are the questions associate professor of physics David Bradley and several Vassar students are attempting to answer under the auspices of the college’s Undergraduate Research Summer Institute.

In one project in Kenyon Hall, Ariana Sharma ’14 and Ian Kowolok ’16 are attaching dozens of weirdly shaped plastic panels to the walls and ceiling. Using a high-tech array of cameras and microphones, they are mapping how the sound in the room travels.  Bradley says the results of this summer’s research can help architects design more acoustically pleasing spaces. “Acoustics is a combination of art and science, but the more data you have about how the sound in a room travels, the closer you are to a science,” he says.

Sharma, a physics major from Katy, TX, first became interested in acoustics during her freshman year when she saw some articles on the subject Bradley had tacked onto a bulletin board outside his office. “Both of my parents are musicians, and I’d been in choirs all my life, so sound is something I’d always been interested in,” she says. “I did some acoustics research for Professor Bradley last summer, and what we’re doing this summer is a continuation of that.”

Researchers often bounce sound off oddly shaped panels, called diffusers, to track its behavior, Sharma says. But they usually use only one or two diffusers at a time. Using many of them at once is something new, she says, and measuring the data has been a challenge. First, Sharma and Kowolok had to find a way to attach all the panels. Then they had to devise software that would accurately translate the sound waves onto a graph on a computer screen. “We’re finding out there’s a reason no one has ever tried to put 200 diffusers in the same room, and fiddling with the software was one of our first hurdles,” she says.

Kowolok, a physics major from Elizabethtown, PA,  says encountering unexpected problems, and then solving them, is part of the challenge of original research. “It’s different from what we do in the classroom because there aren’t necessarily clear-cut solutions to the problems we face,” he says. “If the software is being uncooperative, you can’t just open a textbook and find a solution.”

Kowolok says he’s enjoying learning multiple aspects of the art and science of acoustics. In addition to the experiments Kowolok and Sharma are performing with those oddly-shaped panels in Kenyon, Bradley is overseeing two other projects with  URSI students, one involving a reverberation chamber that bounces sound efficiently and another in a lab in a nearby IBM facility that completely absorbs sound waves.

“Working on this team has been a fun and a learning experience for me, Kowolok says. “We all have separate projects, but come together whenever one of us needs help. I've really enjoyed being exposed to new technologies and methods and getting a taste of what focused physics research looks like.”

Sharma says she’s confident she and her fellow URSI students will have learned enough to write a paper on their findings and deliver it at the annual conference of the Acoustics Society of America in Indianapolis in October. “It’s been fascinating to do this groundbreaking work, where every combination of diffusers yields new results,” she says. “It’s great to be able to devote the time to tackle a project and see it through to the end.”

--Larry Hertz

Posted by Office of Communications Tuesday, July 29, 2014