Nation's Business

When he hears, others listen – Sotirios J. Vahaviolos of Physical Acoustics Corp

When he hears, others listen – Sotirios J. Vahaviolos of Physical Acoustics Corp – company profile

Barbara E. Thornbury

When He Hears, Others Listen

Sotirios J. Vahaviolos is a man whose business is to hear things most people don’t. Sometimes he wishes he didn’t. His work makes him acutely aware of the dangers posed to structures of all kinds by metal fatigue.

Take airplanes, for example. A plane is like a balloon, Vahaviolos explains. When pressurized from inside, it expands. When pressure is released, the plane contracts. That process occurs over and over again during the life of a plane. After enough cycles, cracks will appear in the fuselage. If the airlines did not make repairs, those cracks could get bigger and bigger, and the plane could come apart.

Just as people groan when they have aches and pains, structures make noises when they are under mechanical stress. Vahaviolos, 43, has built a company on that fact: He is founder, president, and chief executive officer of Physical Acoustics Corp., a Princeton, N.J., firm that develops and manufactures instruments to detect acoustic emissions. Those are the high-frequency noises that can reveal structural weaknesses in everything from airplanes to bridges to storage tanks to high-pressure steam pipes.

Vahaviolos grew up in Greece, where as a child he ripped apart machinery and rebuilt it for fun. He came to the U.S. to study engineering at Fairleigh Dickinson University, in New Jersey, and went on to get his M.S. and Ph.D. in electrical engineering from Columbia University.

He started his career at American Telephone & Telegraph’s Bell Laboratories, where the concept of acoustic emissions was developed in the late 1940s. When Vahaviolos came along 20 years later, he worked out computerized solutions to the long-standing problem of how to filter out irrelevant background noises during acoustic-emission testing.

With the backing of several venture-capital firms, Vahaviolos struck out on his own in 1978, to explore industrial applications for acoustic-emission technology. AT&T gave him its blessing, in the form of a license to use technology he had developed while working at Bell Labs; it also became his first customer.

Physical Acoustics makes sensors–specialized microphones about the size of champagne corks–that can pick up acoustic emissions when they are placed on the surface of a structure. Cables carry that information to small computers that analyze it and display the locations of the noises. In that way, problem areas can often be located before they could be detected by other methods, such as visual inspection. Because structures need not be dismantled before they are tested, the acoustic-emission method is called nondestructive testing.

Physical Acoustics sells a basic testing system for between $25,000 and $100,000. Vahaviolos says the $25,000 system would be sufficient to test an airplane’s wing, but a $100,000 system would be needed to test an entire Boeing 747. Physical Acoustics provides training in the use of its equipment that ranges from a few days to a month, depending on how much a client already knows about nondestructive testing.

Approximately 70 percent of the company’s business comes from the aerospace, petrochemical, and utility industries; the rest is from research institutions and materials-testing labs. Half of Physical Acoustics’ income comes from outside the U.S.; Vahaviolos was one of the first foreign scientists invited by the Soviet Union to inspect the site of the nuclear power plant accident at Chernobyl.

Although the privately held company’s sales have been growing more than 30 percent a year–revenues this year will be around $17 million–and it now has 150 employees, Vahaviolos says that many people in business and government have been slow to abandon older inspection methods.

“Some people thought I was crazy, listening to abnormal material sounds,” Vahaviolos recalls, “but acoustic-emission nondestructive testing is an industry now.”

And, he adds, “we believe very strongly that we can avoid catastrophes.”

PHOTO : A sensor like the one Sotirios J. Vahaviolos is holding can pick up high-frequency noises

PHOTO : that warn of defects in aging aircraft. The locations of those noises can then be

PHOTO : displayed on a computer screen.

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