The noise that jolts Annie Tulkin and her husband awake in the middle of the night vibrates their bed and sounds like a jackhammer going off intermittently inside the walls of their Silver Spring home, she said.

The pounding and shaking that began three weeks ago can start at 1 a.m., 3 a.m. or anytime in the dead of night, Tulkin said. Her husband sticks in earplugs while she retreats to their quieter guest bedroom upstairs, hoping their 3-year-old daughter sleeps through it.

Tulkin has traced the nighttime racket to a massive machine hammering through bedrock while excavating a 1,000-foot tunnel that, in four years or so, will carry light-rail Purple Line trains beneath her neighborhood off Plymouth Street, just east of downtown Silver Spring.

“You can’t be waking up babies and toddlers at 3 a.m. — that’s just not acceptable,” Tulkin said. “We all accept that it’s a construction zone. But at 3 a.m.? No.”

What angers Tulkin and many of her neighbors most is that the Maryland Transit Administration (MTA) appears to have been well aware that the tunneling, which is allowed 24 hours a day, seven days a week, would be particularly disruptive. In a little-known 2016 memorandum of understanding, state and Montgomery County officials agreed that the tunneling would be exempt from local limits on construction-related noise.

“They were fully aware that this would cause noise and problems for people,” said Tulkin, who otherwise supports the Purple Line. “They essentially decided people’s sleep doesn’t matter to them.”

At a tense public meeting Tuesday night, about 30 residents received sympathy, but no relief from Maryland transit officials.

Mike Madden, MTA’s deputy project director on the Purple Line, said prohibiting the overnight excavation would delay the entire 16-mile project because the tunnel’s construction is critical to the overall schedule. The agreement with the county, Madden said, provided a “blanket noise waiver” for the tunneling.

“We regret that it’s that disruptive,” Madden told residents. Later, he added: “At this point, the state is not prepared to stop work or [direct] the contractor to not go on for 24 hours at the tunnel because that’s necessary to meet the schedule.”

Project officials said the noisiest work will be finished in about six months — too long for many residents.

Neil Fagan said he, his wife and their 2-year-old daughter can’t sleep amid the banging. Fagan said he often lies awake for two hours trying to get back to sleep, and even ample coffee can’t keep him from dragging the next morning.

He questioned why state transit officials, who control the schedule, agreed to a contract allowing such disruptive nighttime work — and why they won’t change it now that residents are losing sleep.

“They haven’t thought about the human beings this impacts,” Fagan said. “They just signed a waiver to let [the contractor] drill holes in the night without consulting the people it affects. It just seems immoral.”

Montgomery Council member Tom Hucker (D-Silver Spring) said he’s frustrated that the state won’t restrict the tunnel boring to mostly daytime hours, as it has for blasting.

“I want the project to finish on time as well, but if it means a minor delay to give my constituents some relief in the middle of the night, I’m fine with that,” Hucker said. “They’re gung-ho to finish on time, regardless of the human costs.”

Maryland transit officials did not respond Wednesday to questions seeking further explanation.

Tim Cupples, Montgomery’s liaison to the Purple Line project, told residents that the county lacks any authority to require the state to follow local noise ordinances. However, he said the 2016 agreement provided “some level of protection” for most areas along the alignment.

The agreement also granted a noise waiver for weekday pile driving, work within the Silver Spring Transit Center, and construction between Colesville Road and the intersection of Ramsey Avenue and Bonifant Street in downtown Silver Spring.

The tunnel is being excavated east to west, starting near the Giant grocery store on Arliss Street at Flower Avenue, traveling beneath Plymouth, and ending just east of Wayne Avenue. Project officials have said it’s necessary because the area’s topography is too steep for light-rail trains to travel above ground.

The top of the tunnel is about 40 feet below homes, said Carla Julian, spokeswoman for the Purple Line contractor.

Julian told residents the state would have to direct the contractor to stop working at night.

“We feel for them, we’re super sympathetic,” Julian said of the residents. “We talk all the time about if there’s anything we can do within the parameters of the contract to help them.”

Julian said one resident stayed in a hotel temporarily, at the project’s expense. Other residents, she said, say doing so is impractical, especially with children and pets.

Del. Jheanelle Wilkins (D-District 20), who represents the area, told Maryland transit officials they need to do more to help residents.

“We can’t just ask residents to not sleep or to sleep in a hotel and take their kids and dogs with them,” Wilkins said. “That is not reasonable. We need to come to the table and figure something out.”

Cupples said the county “has done and continues to do all we can to advocate with the state” on residents’ behalf. While the county couldn’t require the state to follow its noise ordinances for the tunnel work, he said, it did convince the state to abide by them “in most cases” elsewhere along the Purple Line alignment.

“Unfortunately,” Cupples said, “they did not agree to do so at the Plymouth Tunnel.”