Back in 2006, Nike introduced the high-performance SUMO 2 golf club driver, specially engineered to help golfers hit straighter shots, even for slightly off-center hits. There was just one problem: the newly designed club made an unpleasantly loud, tinny sound when it struck the ball—so much so, that most players proved unwilling to tolerate it, even in exchange for improved performance.
Scientists have now pinpointed the problem: the bottom of the club head (called the sole) vibrated at frequencies that fell smack in the most sensitive range of human hearing. That’s the conclusion of Daniel Russell, an acoustician at Pennsylvania State University, who described the results of his latest experiments earlier today at a meeting of the Acoustical Society of America in Salt Lake City, Utah. A paper is pending publication in the Journal of the Acoustic Society of America.
Russell has been researching the acoustics of sports equipment for the past 18 years, spanning everything from the various types of baseball bats to hockey sticks and tennis rackets. Last summer, he heard that Nike Golf was designing a new line of composite drivers with the goal of addressing that unpleasant impact sound. His graduate student, Peter Kerrian, happened to be an avid golfer—and was also in need of a research project for his master’s thesis.
That’s how Russell and Kerrian ended up collaborating with Nike to investigate the acoustic properties of the problematic golf club. “Some players compared the sound to a cookie tray hitting the top of a car,” Russell said in a statement. “It was such a different—some say annoyingly loud—sound, it raised eyebrows.”
Members of Penn State’s golf team gamely hit a few balls with the noisy golf club, and Russell and Kerrian recorded and analyzed the resulting sounds. They found that those sounds peaked in the 2-3 kilohertz range—right where the human ear is most sensitive.
Kerrian likens the sound of impact from the SUMO 2 to the tin-can ping of an aluminum baseball bat—a pet peeve of avid baseball players, who generally prefer the satisfying crack of a wooden bat. Diehard golfers are just as particular about how their clubs sound in action.
“I am always amazed how strongly the sound of the club-ball impact matters to players, not just in golf, but also in baseball, softball, and tennis,” Russell told Gizmodo. “If the club, bat, or racket doesn’t sound ‘right’—whatever ‘right’ means—then players usually are not willing to use that club, regardless of how high performing it might be.”
Based on these measurements, Russell thinks the Nike SUMO 2 club could be redesigned to dampen the annoying sound without sacrificing the improved performance—perhaps by incorporating different sound-absorbent materials. Player preferences with regard to sound may also be shifting, given the current trend away from pure titanium clubs and toward composite drivers. In fact, newer designs using ultra-lightweight composite materials are actually too quiet.
Acoustics can help find a happy medium between the two extremes, according to Russell: “Understanding how and why clubs make the sounds they make is the first step toward helping sports engineers design clues that sound ‘just right,’ while still hitting the ball straight and far.”