It sounded like popcorn warming in a microwave: sporadic bursts that quickened, gradually, to an arrhythmic clatter.

“There it is,” Mary McKee said, staring out the front door of her home in Arlington, Va., on a recent afternoon.

McKee, 43, a conference planner, moved to the neighborhood in 2005 and for the next decade and a half enjoyed a mostly tranquil existence. Then came the pickleball players.

She gestured across the street to the Walter Reed Community Center, less than 100 feet from her yard, where a group of players, the first of the day, had started rallying on a repurposed tennis court. More arrived in short order, spreading out until there were six games going at once. Together they produced an hourslong ticktock cacophony that has become the unwanted soundtrack of the lives of McKee and her neighbors.

“I thought maybe I could live with it, maybe it would fade into the background,” she said of the clamor, which began around the height of the coronavirus pandemic and now reverberates through her home, even when her windows are closed. “But it never did.”

Sports can produce all kinds of unpleasant noises: referees’ whistles, rancorous boos, vuvuzelas. But the most grating and disruptive sound in the entire athletic ecosystem right now may be the staccato pop-pop-pop emanating from America’s rapidly multiplying pickleball courts.

The sound has brought on a nationwide scourge of frayed nerves and unneighborly clashes — and those, in turn, have elicited petitions and calls to the police and last-ditch lawsuits aimed at the local parks, private clubs and homeowners associations that rushed to open courts during the sport’s recent boom.

The hubbub has given new meaning to the phrase racket sport, testing the sanity of anyone within earshot of a game.

“It’s like having a pistol range in your backyard,” said John Mancini, 82, whose Wellesley, Mass., home abuts a cluster of public courts.

“It’s a torture technique,” said Clint Ellis, 37, who lives across the street from a private club in York, Maine.

“Living here is hell,” said Debbie Nagle, 67, whose gated community in Scottsdale, Ariz., installed courts a few years ago.

Modern society is inherently inharmonious — think of children shouting, dogs barking, lawn mowers roaring. So what makes the sound of pickleball, specifically, so hard to tolerate?

For answers, many have turned to Bob Unetich, 77, a retired engineer and avid pickleball player, who became one of the foremost authorities on muffling the game after starting a consulting firm called Pickleball Sound Mitigation. Unetich said that pickleball whacks from 100 feet away could reach 70 dBA (a measure of decibels), similar to some vacuum cleaners, while everyday background noise outside typically tops off at a “somewhat annoying 55.”

But decibel readings alone are insufficient for conveying the true magnitude of any annoyance. Two factors — the high pitch of a hard paddle slamming a plastic ball and the erratic, often frantic rhythm of the smacks — also contribute to its uncanny ability to drive bystanders crazy.

“It creates vibrations in a range that can be extremely annoying to humans,” Unetich said.

These bad vibrations have created an unforeseen growing pain for pickleball, which emerged from relative obscurity in recent years to become the fastest-growing sport in the country.

The sounds were even dissected last month at Noise-Con 2023, the annual conference of North American noise control professionals, which featured an opening-night session called “Pickleball Noise.”

“Pickleball is the topic of the year,” said Jeanette Hesedahl, vice chair for the conference.

The same story, the same jarring sound, has echoed across American communities like rolling thunder.

Sue-Ellen Welfonder, 66, a best-selling romance novelist from Longboat Key, Fla., once enjoyed listening to the singing birds and the gentle swish of trees during her daily walks — her “soul balm time” — through a local park. The thump-thump of a tennis match never bothered her, either. But the arrival of pickleball this spring, she said, shattered her idyll.

“Pickleball has replaced leaf blowers as my No. 1 noise nuisance,” said Welfonder, who has been sketching the outlines of a new novel, set in the present day, with a couple of pickleball-loving characters: “I’m making them really nasty people.”

The complaints were equally dramatic at a Feb. 6 city council meeting in West Linn, Ore., where residents have been vexed by the constant click-clacking from Tanner Creek Park.

“One of our neighbors who lived directly across from the courts and was dying from cancer noted the pickleball noise was worse than his cancer,” Dan Lavery, a West Linn resident, said at the meeting. “Sadly, he recently passed.”

Scores of similarly suffering Americans are finding their way to a rapidly growing Facebook group, also started by Unetich, where upward of 1,000 frazzled users exchange technical advice, let off steam and engage in a sort of group therapy.

“We try to keep it civil,” Unetich said, “because it gets pretty emotional.”

A few lessons have crystallized within the group. Soundproof barriers — a go-to solution for many at first — can be expensive and are often improperly deployed. New paddles and balls designed to dampen noise have had marginal uptake among players. Moving pickleball far away from human life may be the only surefire solution — but many are slow to reach that conclusion, which presents its own hurdles.

Irritated homeowners, as a result, often resort to fighting pickleball courts in the courts of law.

Last year, Rob Mastroianni, 58, and his neighbors in Falmouth, Mass., filed a lawsuit against their town claiming that the courts near their homes violated local sound ordinances. They won a temporary injunction, which has closed the facility for now. By then Mastroianni had already sold his house and moved to a different part of town to escape the noise.

“I was Google Mapping the new house, making sure there were no courts nearby,” Mastroianni said.

In Arlington, McKee and her neighbors around the community center are waiting to see what happens next. They shared their pain with the county, which for now appears to be moving forward with plans to spend close to $2 million to make the pickleball courts permanent.

The players there sympathized with the residents’ plight — but only to an extent.

“If I had that home, I’d be mad, because it is annoying — it’s obnoxious,” Jordan Sawyer, 25, a dietitian from Arlington and an avid player, said between games this month. “But I don’t feel bad because I want to play, and this is the best place to play. Honestly, I just feel like it’s unfortunate. It’s unlucky for these people.”

Sawyer described herself as a “rule follower.” But McKee and the others recounted being woken up at 3 a.m. by middle-of-the-night pickleball matches. Another time they listened to a player banging a tambourine on the court, apparently to taunt those who had complained.

Armand Ciccarelli, 51, who often walks his dog, Winona, around the community center, said that anybody downplaying pickleball noise should try hearing it for 12 hours a day.

“I know this seems like a small thing in the grand scheme of the world, where we’re dealing with big things, like climate change,” Ciccarelli said. “But, as you can see, it’s a nationwide problem.”

Kitty Bennett contributed research.