Vijay Singh, the world’s No. 3-ranked golfer, is poised to win the PGA Tour’s FedEx Cup, its yearlong playoff, in less than two weeks. His points lead is so large, in fact, that he needs only to complete the Tour Championship on Sept. 25-28 to clinch the victory.

But before Singh won three of the last six PGA Tour events, he had not won in 17 months.

So what is responsible for the turn-around? According to Singh, his newfound consistency comes from the Sonic Golf S-1, a new device developed by Yale applied-physics professor Robert Grober.

With curly brunette hair and sun-kissed skin, Grober looks more the part of a golf pro than the Frederick Phineas Rose Professor and director of undergraduate studies in the Applied Physics Department. During his time as a Division I golfer for Vanderbilt University, Grober even aspired to become a golf professional. But upon realizing that graduate school offered more reliable career prospects, he took his love for golf and turned it into a physics doctorate from the University of Maryland.

Grober said he has always enjoyed “using sensors in and around golf clubs,” but his hobby morphed into a company, Sonic Golf, with the creation of “System 1,” a device that slips into the shaft of a golf club and allows golfers to monitor the timing and rhythm of their swing by electronically translating speed into sound heard through a headset.

“It gets the data off the sensor wirelessly,” Grober said, “and it is broadcast to a unit that is attached to your hip, much like an iPod.”

From the hip unit, the golfer hears through a headset a series of sounds, which range from low-pitched and soft to high-pitched and loud, depending on the club’s velocity. The sounds do not indicate when a swinging error is committed, but they allow golfers of every level to hear the audio manifestation of their swing.

Grober said golfers at different levels of expertise focus on different portions of the swing. Beginning golfers with little experience getting the ball from the tee box to the fairway are much more likely to focus on the sound tempo and on increasing consistency, he said. More intermediate golfers look to ensure that their maximum speed (determined by higher pitch and volume) occurs when the club meets the ball. And golfers at the highest level analyze the transition between the backswing and downswing — the device gets louder as the club reaches the top of the swing and quiets in the pause before the downswing. By monitoring the length of the pause at the top of the swing, top golfers can carefully adjust the transition from backswing to downswing.

Peter Pulaski, director of golf operations and PGA teaching professional at The Course at Yale, said he has witnessed the S-1 device develop over time, as Grober used the course’s driving range as a test facility. The harmonics of the device provide a beneficial learning experience for golfers at all levels, Pulaski said, allowing them to become more comfortable with their own tempo.

“I think it’s a great learning tool for people who are struggling with the golf swing,” he said. “It’s something you can do on your own. Educators can talk about the golf swing, but the person has to make it theirs.”

Pulaski said he plans to purchase the S-1 tool to teach lessons as soon as the next batch comes off the assembly line.

Although Grober jokes he has referred to the device as a “thingamajig” and “whatchamacallit,” he said it stands out from other golf aids on the market because it is a “completely different modality,” using sound as the instructor.

“The conventional way of learning in golf is interacting with a teacher and then going to video,” he said. “This relates to tempo, timing and rhythm in the golf swing, which are three aspects of golf which are difficult to learn about.”

Grober’s S-1 may be impacting the golf swings of pros like Singh, but Grober said the process of starting a company has swallowed much of the time he spent working on his own game. Sonic Golf is in the beginning phase of business, but Grober says the company is working on acquiring office space in nearby Woodbridge. In an effort to keep the company Connecticut-based, he has contracted with Tri Town Precision Plastics to produce the shaft insert and Silicon Integration to assemble the electronics.

Initially, only 10 demos of S-1 were created for tour professionals, but Grober said Sonic Golf hopes to make 250 by Oct. 15 and will eventually be producing in lots of 1,000.

The product is limited to professionals right now, but some Yalies will get the opportunity to experiment with the technology: Grober is teaching a this semester — “Physics of the Game of Golf” — inspired by the quantitative data derived from the S-1 device.

Men’s golf captain Colby Moore ’09 said the Yale golf teams had opportunities to test the product during its development, allowing them to attempt to replicate the sound of pros’ swings and develop their own rhythm.

“[Grober’s] pretty much told us that we can e-mail him when we want to use it,” Moore said. “We’ve kind of been his guinea pigs year-round.”

So how did S-1 get from the Yale bubble into Vijay Singh’s grip?

“There’s a great question,” Grober said. “You go out and you show people, and if people like it, they go out and show someone else, so you are never too many introductions away from everybody.”

And if the S-1 is on par with likely FedEx Cup champion Vijay Singh’s standards, the product may soon be Grober’s hole-in-one in the golfing market.