Minneapolis ? Hospital noises during the night can approach the levels of chain saws or jackhammers, making it nearly impossible for patients to sleep, according to a new study at the Mayo Clinic.

The nurses found that steps as simple as closing the door to a patient’s room and stifling the clatter of clipboards can help.

Cheryl Cmiel, a nurse at the clinic in Rochester, started the study after hearing patient complaints. She and other researchers placed noise-measuring devices in three empty patient rooms at Mayo’s St. Marys Hospital during a night shift, without the knowledge of other nurses.

They found peak noise readings of 113 decibels, usually around a nursing shift change at 7 a.m. The average noise level was 45 decibels, slightly less than you might find in a library. Noise-reduction efforts reduced the peak to 86 decibels and the average to 42.

A chain saw can produce 120 decibels, according to the League for the Hard of Hearing.

Cmiel and nurse Dawn Gasser also slept overnight in a room set up with the equipment normally found in a thoracic unit, where patients recover from chest operations.

Gasser wrote in the study, being published in the February issue of the American Journal of Nursing, that she was awakened by her roommate’s IV pump alarm at 1:15 a.m. She was awakened again at 3:15 a.m. when the portable X-ray machine was rolled into the room, sounding “like an oversized power tool as its motor whirred and the cartridges of X-ray film bumped noisily together.”

At 6:10 a.m., she was roused by the tapping of a doctor’s dress shoes in the hallway, and she opened her eyes to full-strength lighting in the hallway just outside her door.

“I realized it would be even more frustrating for the patients, who would also be dealing with pain, and having tubes going into their bodies,” Cmiel said in an interview. “It really was an eye-opener.”

Other hospitals have similar or worse noise problems. The recovery area for new mothers at Abbott Northwestern Hospital in Minneapolis is next to the helipad, and the same unit at Hennepin County Medical Center is across the street from Minneapolis’ Metrodome, site of monster truck rallies, dirt bike races and Minnesota Twins night games.

At the nurses’ suggestions, rubber pads now cushion the bottom of metal chart holders in the thoracic unit to quiet the clunk of clipboards. Signs ask visitors to stay quiet. Nightly X-rays are performed less often, and at 10 p.m. instead of 3 a.m. Noisy roll-type paper-towel dispensers have been replaced by quieter folding-towel dispensers.

Mayo patient John Foy noticed the difference.

“I was pleasantly surprised, because I had heard stories from friends and neighbors” about not being able to sleep in a hospital room, said Foy, 63, of Bermuda Dunes, Calif.

“Little by little we are seeing more nursing units within our hospital doing the same things,” Cmiel said. “We found it was a very easy thing to do.”