NEW YORK — In the history of tennis, a small number of players have possessed the ability to make a crowd gasp. From the sheer venom of an Andre Agassi return to the beauty of a Roger Federer half-volley and the crack of a Juan Martin del Potro forehand, a chosen few have had the gift.

And then there is the sound of a Jannik Sinner forehand.

The Italian’s groundstrokes are the bedrock of his game, the power and speed of his shots keeping his opponents under pressure throughout. They were a key factor in earning him his first Grand Slam title, at the Australian Open in January, and have been integral to his rise to the world No. 1 ranking.

Sinner came into the US Open last week surrounded by the recent news that he had tested positive twice in March for traces of a banned steroid. He escaped a ban when anti-doping authorities accepted that he had been accidentally cross-contaminated via a spray used by his physiotherapist to heal a cut on his finger.

Despite the controversy, Sinner has looked all but unstoppable, getting through his matches at Flushing Meadows with relative ease. With Carlos Alcaraz and Novak Djokovic gone early, he is the favorite for the title, and will face Daniil Medvedev in the quarterfinals on Wednesday. Through it all, he has relied on that unique forehand.

And it’s not just the speed, power, accuracy or technique. It’s also the sound, especially on his forehand, his long levers and high racket-head speed allowing him to whip the ball through the court with a crack. It was the first thing that Darren Cahill, who joined Sinner’s coaching team in the summer of 2022, noticed.

“The sound of the ball when he hits it, it’s pretty amazing, isn’t it?” Cahill told reporters in Melbourne earlier this year.

“Agassi hits the ball like that. When he hits the ball, it just sounds like it’s hit harder than everybody else. Rafa [Nadal] was exactly the same. Roger [Federer], when he hit a forehand, you could just hear the sound of it. And Novak [Djokovic], when he hits a forehand and backhand, it’s like a thud. It’s not just a normal person striking the ball. All those players have a different sound when they hit the ball and Jannik certainly has that as well.”

According to TennisViz, a company that analyzes the ATP Tour, the speed of Sinner’s forehand has remained remarkably similar ever since he broke onto the Tour. At an average of 78 mph, it’s 5 miles per hour faster than the Tour average. But as he has added strength and as his body has filled out, his revs have increased markedly. In his first year on Tour — 2021 — Sinner averaged 2,883 rpm. In 2024, it’s 3041, way above the Tour average of 2,708. That, too, affects the sound the ball makes when it leaves his racket.

“The sound of the ball when he hits it is unique and special,” Cahill said. “He gets that from his timing and his hand speed. He’s worked damn hard to be able to do that. One of the toughest things we have as coaches is to stop him from practicing. He will play nonstop on the court.”

Former players and coaches are in awe of the Sinner forehand.

For Thomas Enqvist, a former world No. 4 and now a leading coach, it brings to mind one of the biggest hitters of all time.

“It’s true that it has this special sound,” he told ESPN. “It reminds me a little of the way Pete Sampras hit the ball. Remember we called him Pistol Pete, it’s like a whip almost, it comes out with such a force, with such an effect. When we say that the ball ‘goes through the court,’ we mean that when the ball bounces, the ball just kind of like spins away. I played Pete many times, that’s how it felt when you’re playing him. It’s not always like the speed of the ball, it’s actually how the ball reacts when it hits the surface. Jannik reminds me a lot of him.”

Other players have great forehands. Alcaraz can unleash immense power when he goes flat-out; Djokovic’s forehand zips through the court and Andrey Rublev creates immense racket-head speed when he hits the ball. But the sound of the Sinner forehand is different.

James Blake, another former player who was blessed with huge power on the forehand, said some of the “crack” sound comes from the strings Sinner uses.

“It’s a huge forehand,” he told ESPN. “It’s one of the biggest forehands in the game right now but I think part of the sound difference is he’s one of the few guys now — a man after my own heart — who strings his racket real tight.

“I want to say it’s around 62 pounds or something. Mine was a 68 my whole career so I think it sounds different because it doesn’t have that same trampoline feel and sound. And obviously he swings so hard that it just has that different sound and he hits the ball clean the whole time. In terms of the actual results, it’s just a huge shot.”

Like Cahill, former world No. 2 Tommy Haas compares Sinner’s ball-striking to Agassi. “I remember growing up watching Andre Agassi practice when I went to Nick Bollettieri’s [academy], when he unleashed the forehand and even the backhand, and I was always in shock and awe,” he told ESPN. “I was like, ‘I’ve got to try to hit my forehands like that if I can.’ I feel like the same way with Jannik now — I think the consistency, the control, he can just rely on those things.”

Sinner doesn’t see himself as special, however.

“It’s tough from my point of view, it’s tough to understand when someone says, ‘Look, you are special or you’re a good player,’ because you know only yourself,” he said in Melbourne. “You cannot touch the ball what you are hitting in the other side.”

Sinner may not be able to touch it, but there’s no mistaking that sound.