• It’s the thwacking — loud and endless — that drives them up the wall, say people who live near pickleball courts in Chestnut Hill.

• It’s the neighbors — always complaining — that spoil exercise and camaraderie for pickleball players enjoying fresh air in a public space.

• In the second-most expensive community in Philadelphia after Rittenhouse Square, an ongoing fight about pickleball may seem like a trivial sort of NIMBY (Not In My Backyard) grievance.

• But this one has flared into a consequential dispute.

“When people get upset about something placed in their neighborhood, it’s usually not pickleball but something like safe-injection sites that they don’t want — which I support, by the way,” said Deirdre Dingman, a professor at Temple University’s College of Public Health who plays pickleball at the courts and lives around the corner, undisturbed by the din.

Actually, pickleball, now boasting nearly 5 million players, is roiling communities everywhere as it grows more popular, spawning anger and lawsuits throughout America. Overall, there are an estimated 2,000 regular Philadelphia pickleball players, according to Braden Keith, a community organizer who runs the Philadelphia pickleball Facebook page.

In Chestnut Hill, the rear property lines of two-story brick rowhouses on the 8100 block of Ardleigh Street sit just 14 feet from lighted pickleball courts at Water Tower Recreation Center, managed by Philadelphia’s Department of Parks and Recreation.

It’s one of five outdoor pickleball courts run by the department, said a Parks and Recreation spokesperson, who added that, despite complaints, “The pickleball courts are not moving from Water Tower Recreation Center.”

Wooden or graphite paddles striking hard-plastic balls perforated like Wiffle balls create a loud noise, less than a second in duration, at a piercing, high-pitched frequency to which the ear is quite sensitive, according to engineer Lance Willis of Spendiarian & Willis Acoustics & Noise Control in Tucson, Ariz.

Hearing pickleball smacks all day “just drains the energy out of you,” said a 79-year-old neighbor who asked not to be identified because he says pro-pickleballers have harassed him.

Players, many of whom flocked to the sport to occupy themselves during the height of the pandemic, sympathize with the neighbors — to a point.

Player Leonard Dow, 58, of Mount Airy, who works in financial services, said, “I recognize what the neighborhood is saying, but we’re giving them laughter, diversity of age and race. That’s what city life is about.”

After her game, Mary Illari, 62, a school nurse at Building 21 High School in West Oak Lane, said she’s heard the complaints and has just one observation:

“You shouldn’t buy a house near a court.”

Don’t say that to people who were living on Ardleigh years before the city spent nearly $100,000 to convert three tennis courts into six pickleball courts in 2016. Neighbors said that at the time, they were unaware that the conversion to accommodate the burgeoning appetite for pickleball was occurring.

“I loved the sound of tennis,” said Sarah Bettien-Ash, 45, who’s lived on the 8100 block for 15 years, and runs a holistic health business.

Neighbors say they’re contemplating a lawsuit against the city. They contend the pickleball courts violate Philadelphia’s noise ordinance, which states that sound from a nonresidential property reaching five decibels above background levels is excessive.

According to the Environmental Protection Agency, ambient background noise in most cities ranges from 60 to 70 decibels, though quiet neighborhoods register 45 to 50 decibels. The pickleball neighbors say they’ve measured 80-to-90-decibel days on the courts.

Normal conversation is about 60 decibels and a running motorcycle engine is about 95 decibels, according to the Centers for Disease Control and Prevention.

Overall, tennis balls are softer, and strung rackets have more give, making struck tennis balls about 25 decibels less loud than pickleballs, said Willis. Tennis hits are also an octave lower than pickleball pitch, he added. Scientists say average tennis players reach 40 decibels per strike, putting similarly skilled pickleballers in the 65-decibel range. Better players hit harder and louder.

Heidi Grunwald, director of Temple’s Institute for Survey Research and a pickleball player at Water Tower, said she requested that the university’s College of Engineering measure playing noise there.

Researchers said their work isn’t completed yet, but Grunwald added that the decibel level is closer to that of ambient sounds, nowhere near 90.

Still, Grunwald acknowledged, “I wouldn’t want to live with this sound outside my door.”

While the noise is bothersome, it’s not medically dangerous, said Robert Sataloff, chairman of the department of otolaryngology at Drexel University College of Medicine.

He suggested that people are so riled by pickleball because humans seem to be programmed by evolution to react to high-pitched sounds, like a baby’s cries.

“It’s psychological annoyance,” he said, “a quality-of-life issue.”

Environmental psychologist Arline Bronzaft, who lives in New York, agreed: “The sound is stressful and makes you unhappy. How’d you like to live like that?”

The city is striving to “find a balance between the needs of site users and the neighbors of our parks,” the Parks and Recreation spokesperson said.

To accommodate neighbors, the city reduced hours at the courts by 30%, limiting play times to 1 p.m. to 8 p.m. Monday through Friday, and 9 a.m. to 5 p.m. on Saturdays. No play is permitted on Sundays. Additional pickleball courts will be created at Awbury Recreation Center in Germantown, which aren’t as close to homes, to lighten usage at Water Tower, the spokesperson said.

Meanwhile, to help pay for possibly soundproofing the courts, the Chestnut Hill Community Association has pledged $5,000, said Keith Kunz, the Water Tower Advisory Council president. Grunwald said 15 players have raised an additional $3,000 for that purpose. Sound-muffling curtains or walls would cost around $30,000 and would reduce 50% of the noise, Kunz said. Neighbors have said they won’t pay.

None of that may even matter, Willis said.

“With houses just 14 feet away, you might need a 20-foot wall around the courts,” he said. “And even that probably wouldn’t do much. We like to see at least 100 feet distance between homes and courts.

“I’d say the courts are too close.”

To address that, a few people suggested swapping more distant tennis courts at Water Tower with the pickleball courts. But that could cost $150,000, according to one estimate by Braden. Others suggest quieter foam balls; but players say they don’t bounce the same. The best solution, several neighbors say, is shuttering the courts permanently.

“People say we’re ridiculous to go on about all this,” Bettien-Ash said. “But, believe me, if this was your house near all this noise, you’d understand.”

Staff writer Ryan Briggs contributed to this article.