The helicopters typically come in threes.

As the first one flies by, the walls of Kathy Daniel’s Bethesda, Md., home start to shake. When the second follows, the chains on the metal lamps in her living room begin jangling. The brass lamp her father brought home from the Bahamas goes “clink, clink, clink.” The lamps with sailboat finials make a “boing, boing, boing” sound.

“Then the third one goes by, and at that point my nerves are rattled,” said Daniel, 63, a retired communications expert who has lived in Bethesda for more than 30 years. “It’s loud enough where I can’t think straight. It makes my heart pound, actually — I can just feel my blood pressure going up.”

The cacophony lasts at least three minutes and repeats over the course of the day. Helicopters fly over Daniel’s home in the morning, about noon, in the evening and again late at night. Monday through Friday. The air traffic was not always this bad, Daniel said. As best she can estimate, it got much worse starting three or four years ago.

She is not alone. Following a sharp spike in complaints from D.C.-area residents about the frequency and severity of helicopter noise, local lawmakers in January asked the Government Accountability Office to study the issue. Earlier this month, the GAO accepted the request and will launch the study this fall.

Could this study help D.C. residents get relief from helicopter noise?

Rep. Don Beyer (D-Va.), one of the lawmakers who requested the study, said that helicopter noise is “our number one constituent complaint” and that the number of complaints has risen steadily since he took office in 2015.

“Constituents are asking me why the episodes of helicopter noise are increasing and I can’t explain it, I don’t know why,” said Rep. Jamie B. Raskin (D-Md.), who also requested the GAO study. “The study should give us some answers about what is behind the increase in helicopter noise and what can be done to reduce it.”

Meanwhile, households throughout the region live with a level of helicopter traffic that some residents describe as unprecedented and unbearable. The helicopters are impossible to ignore, they say, with their mind-numbing noise that rattles walls, floors, ceilings and nerves.

Daniel said the frequent sound of whirring blades overhead makes her feel as if she is “living in a war zone” — or that she’s a character cowering in a jungle in the 1979 Vietnam War movie “Apocalypse Now.”

She loves her leafy, friendly neighborhood but says she can’t take it anymore. Once she knows where her son will settle after college, Daniel plans to move away.

“For me, it brings up a visceral fear reaction,” said Gabrielle Stevens, 71, a retired environmental scientist who also lives in Bethesda. “It triggers a primitive response in me, that I have to be wary and protect myself, I have to be on guard.”

London-based psychologist Alison Greenwood, who has studied the relationship between noise pollution and mental health, said research has shown that persistent aircraft noise leads to significant emotional and physical stress. It causes annoyance, which in turn increases blood pressure and heart rate. A 2017 study found that aviation-related sounds can raise the risk of heart disease and make it harder for children to do well in school.

Complaints about noise from Washington-area airports skyrocket

“Immediately, I’d be worried particularly about children’s learning,” Greenwood said of the helicopter traffic in the D.C. area.

The helicopters’ possible negative effect on her child has caused Heather Spence, 34, to consider moving out of her home in Arlington, Va., though she has no plans to do so. Spence, a marine biologist on a fellowship at the Energy Department, is expecting a baby in a few months. She said helicopters are “a constant presence” in her neighborhood.

“I know being in a noisy environment causes stress, and now I have another human coming into my care,” Spence said. “It’s different when you’re making decisions for someone else.”

The majority of helicopters flying in the region are probably military aircraft traveling between bases or transporting VIPs, said Seth Clute, director of operations for Maryland-based helicopter company Monumental Helicopters. Weighing around 22,000 pounds, military aircraft are much larger and thus much louder than other kinds of helicopters, he said.

The Federal Aviation Administration is responsible for overseeing flights and setting rules about noise generation, Clute said, but it has a limited ability to regulate military activity.

“The FAA is responsible for the enforcement of federal aviation regulations and can conduct investigative and enforcement actions that can range from remedial training to pilot suspensions, but they can only do that with civil operators,” Clute said. “They can’t do that with [Department of Defense] or military. That’s different, the DOD handles the punishments.”

Clute said he is unsure why military traffic may have increased recently. Residents desperate for answers have resorted to obsessively logging their experiences: One Arlington resident runs outside to snap a picture every time a helicopter flies over. A retiree in McLean, Va., keeps a plastic file box in his basement crammed with helicopter-related newspaper clippings.

William Noonan, a physicist who has lived in Montgomery County for 26 years, said passing helicopters cause his entire house to shake. When he stands in the middle of his family room during a helicopter flight, he can feel the floor vibrating and see the sliding glass doors and windows “flex in and out.”

Helicopters fly above Noonan’s house on average eight times a day, he said. It has gotten so bad — in combination with airplane traffic — over the past three years that Noonan, 57, has begun sleeping in the basement guest room to escape the whirring.

“Every day, we have to straighten all the pictures in our house,” Noonan said, as do his neighbors. “We were talking with a neighbor and the neighbor was like, ‘Oh gosh, you’re right — helicopters are doing it!’ She had been blaming her 7-year-old.”

A few weeks ago, a helicopter shook Noonan’s house so badly that it caused a painting to fall from a wall of his dining room. The 18-by-20-inch portrait came off “right along with the hook and nail — it was nuts.”

Arlington resident Ruth Shearer described a similar experience. When helicopters fly over at low altitudes, her floors rumble, her windows rattle and her two dogs become distressed.

“Look, we’re not naive about living in Arlington,” said Shearer, 56.

“We have VIPs living here. We’ve had motorcades at kids’ soccer games . . . The residents of this area are very, very used to what this area brings, they’re very seasoned, but this is inexplicable,” said Shearer, whose neighborhood is home to the church attended by Vice President Pence.

D.C. Del. Eleanor Holmes Norton (D), who requested the GAO study along with Raskin, Beyer, Rep. Gerald E. Connolly (D-Va.) Rep. Anthony G. Brown (D-Md.) and David Trone (D-Md.), said the fact that experienced Washingtonians are complaining means the helicopter traffic has risen to unlivable levels.

“The tolerance level in this city and region is very high. This is the capital of the United States. We expect helicopters, we expect planes,” Norton said. “You’re dealing with a particularly tolerant population which has had enough.”

Norton and other lawmakers expect that the data gathered during the study will help explain why helicopter traffic has increased, as well as suggest possible ways to reduce the inconvenience to residents.

Among other things, lawmakers have asked the GAO to scrutinize the types of aircraft flying in the region, the frequency of the flights and their flight paths.

Spence is hopeful that the study will reveal “a better way to do things.” She is reminded of what’s at stake every time she looks at her father, who lives with her.

“With him as a [disabled] Vietnam vet with PTSD, it’s not just the physical effects, it’s also the emotional effects of what that brings up,” she said. “He’s not going to say anything about it — that’s not who he is — but I can see it.”

The helicopters “bring back his nightmares,” she said.