Veteran riders won’t be surprised to learn that several stops with reputations for noisiness were, indeed, piercing. Inside the Government Center stop at peak screech, the sound level hit an average of 105 dBA. At Park Street Station, trains rounding a tight corner averaged 111 dBA.

And at Boylston Station, the screech of trains heading east hit an average of 104 dBA, with a peak reading of 115 dBA, on par with a rock concert or sand blaster.

That is way too loud, said Dr. Erica Walker, a sound researcher at Brown University who has analyzed noise levels in Boston and the way that bothersome sounds impact both mental and physical health.

“We shouldn’t automatically say that the louder the decibels, the more irritating it is, because it just depends on the individual,” Walker said. “But I can safely assume that 115 decibels for a train pulling into the station is outrageous. I think it could be viewed as a major community irritant.”

The loudest sounds tend to come when the tracks are bendiest, as they often are downtown, when the flange of train cars’ wheels press and grind against the rails. But they are also noisy on straightaways, when fast-moving trains — including the older ones that have worn and warped with time — rumble in their tunnels, and as train shoes make contact with electrified third rails. The T has been using sound-dampening equipment on its newer cars to cut down on this noise.

A Globe reporter used a sound level meter to capture the decibel readings on the Green Line.Danielle DuBois/Globe

The long-beleaguered T has shown signs of improvement lately, not least of which are the removal of “slow zones” after lengthy shutdowns in recent years. But noise at stations is a stubborn, hard-to-miss side effect of a twisty, turn-y system built eons ago.

To put numbers to the sounds T riders love to hate, the Globe took readings over the course of several days at a selection of infamously noisy spots, using a Tadeto SL720 digital sound level meter.

It recorded sound levels from the run-of-the-mill to the extreme. Some areas averaged 85 dBA, including on the westbound platform of Boylston stop, a level considered safe for sustained exposure.

A Globe reporter used a sound level meter to capture the decibel readings on the Green Line.Danielle DuBois/Globe

Other sections of track reached much higher readings, even without the characteristic screeching on the Green Line. While riding inside Red Line trains between Park Street and Alewife stations, for example, most trips registered at between 80-90 decibels.

But on one day of testing, noise inside a train traveling between Porter and Harvard peaked at 110 dBA, which, according to a chart produced by the National Hearing Conservation Association, is comparable to a power saw at a distance of 3 feet.

On another day, the meter went even higher, hitting 111 dBA between both Porter and Davis stations and between Davis and Alewife stations.

The difference between the lower and higher readings is big: Just a 10 decibel increase in sound is perceived as twice as loud by human ears, experts say.

The T, which also records decibel levels emitted by its trains, said it can be hard to rule out background sounds when taking readings. The agency said T staff who recently rode a new and empty Red Line train from Park Street to Alewife found average decibel levels in the mid-70s.

The Globe experiment didn’t control for the many variables on a busy subway train, including speed, weather, or time of day.

While this reporter has been riding the T for years, he is not a sound scientist.

The sound of MBTA Red Line trains rumbling through the tunnels between Park and Alewife averaged around 90 dBA, but in some cases leaped to above 110 dBA, a Globe analysis found.Craig F. Walker/Globe Staff

But in test after test, the T lived up to its reputation for noisiness.

Here are some of the results, averaged over multiple visits on separate days, in dBA:

• Inside Boylston Station, as trains headed west: 85
• On a Red Line train traveling from Harvard to Porter: 90
• On a Red Line train traveling from Porter to Harvard: 92
• Inside Boylston, as Green Line trains headed east: 104
• Inside Government Center, as trains entered the station: 105
• Inside Park Street, as Green Line trains entered the station: 111

All of these sounds can be unpleasant. But are they damaging?

Probably not, because, according to Meaghan Reed, clinical director of audiology at Mass Eye and Ear, when it comes to sound, timing is everything.

Standards set by the federal Occupational Safety and Health Administration, say workers can be exposed to sounds up to 90 dBA for eight hours a day. For every increase by 5 decibels, the exposure time is cut in half. At 95 dBA, the limit is four hours per day. At 105 dBA, it’s an hour. At 115 dBA, it’s 15 minutes.

“Generally, most riders are not exposed to sound for that long,” Reed said. “So while it can be irritating and uncomfortable while you’re exposed to it, unless that level is significantly louder than that, I wouldn’t expect it to be at a damaging level.”

Headphones, especially when people turn up their music to drown out the sound of public transit, may be doing more damage.

“People are listening to headphones much longer than they’re going through a little corner on the Green Line,” she said.

For its part, the T is aware of how noisy its trains and stations can be.

It records decibel levels during routine inspections, agency spokesperson Lisa Battiston said, and has tried to make it better.

More than 70 “rail lubricators” have been installed to reduce screeching, Battiston said, and new cars have “greasers” that reduce friction.

“This lubrication effort is very nuanced,” Battiston said. “Our teams are always working to make sure enough grease is deployed to mitigate the noisy friction, but not so much as to interfere with train operations and braking.”

There can also be noisy trade-offs. The removal of slow zones on the Red Line, for example, has allowed trains to travel faster. On the Braintree branch, trains are now moving at 50 miles per hour for the first time in 20 years.

And faster trains are noisier.

“As the older Red Line fleet of trains travels faster, there will likely be an increase in the ambient noise,” Battiston said. “However, the sound will be mitigated as we continue to replace the fleet with newer cars.”

Public transit is far from the only source of sound in a city. Trains are noisy, but so are lumbering delivery trucks, barking dogs, helicopters, HVAC systems, the clang-clang of construction work, and on and on.

Over the past week of testing, largely downtown, peace and quiet waxed and waned. When the Parkman Bandstand on Boston Common, a frequent site of noisy protests, was vacant on a recent Wednesday, it registered about 55 dBA.

Inside the Tatte coffee shop next to the Boylston stop, the sound of Ed Sheeran’s “Thinking Out Loud” over the cafe‘s speakers registered at 74 dBA.

A jackhammer being used by a construction crew outside the Old State House, meanwhile, topped out at 110 dBA.

Trains are also not the only noisy things in a T stop: A busker who was singing into a microphone at the State Station’s Blue Line platform registered at 110 dBA.

It’s not clear if lowering all but the loudest of subway noise can meaningfully reduce stress in a city, said Walker, the noise researcher at Brown.

“Mitigating sounds from the MBTA as much as we can would be a great benefit,” Walker said. “But if we quiet that sound, there’s going to be a million other sounds we have to quiet, and a million other stressors we have to deal with.”

Cities, she said, can make a big difference by prioritizing other noise sources, for example by updating building codes to suppress sound that travels through walls and floors.

That way, even if your commute is jackhammer-loud, your bedroom is a place to be at peace.

“We have unlimited wants and we have very limited resources,” Walker said. “I’m always like, ‘Pick your poison.’ ”

Globe correspondent Emily Spatz contributed to this report.

Spencer Buell can be reached at spencer.buell@globe.com. Follow him @SpencerBuell.