Noise louder than roughly the level of conversation can cause premature or sick babies' hearts to beat too fast or too slowly, said Dr. William Engle, a neonatologist at Riley. And interfering with babies' vital signs or sleep can slow development and healing because their bodies do most of that work while they sleep.
"The function of babies is to grow and develop, and in between they eat," he said.
Preemies also need quiet so they can learn their mother's voice and their brains can figure out how to process sound, things that normally happen in the last trimester before birth.
"It's definitely a great idea," Dr. Bob White, a neonatologist at South Bend's Memorial Hospital, said of the monitoring system in Riley's neonatal intensive care unit, or NICU.
White, who is not involved in creating or distributing the system, helped write national noise standards for NICUs that have been adopted by the American Institute of Architects and are used in most hospital design.
Inventor Chris Smith hopes doctors around the country agree with White. He has sold his Sonicu system to several Indiana hospitals and wants to expand nationally.
Smith, 43, had no training as a sound engineer and no plans to become an entrepreneur when his son Sean was born five weeks premature in 2000. But he noticed Sean flinch in response to bright light in the NICU of St. Vincent Indianapolis Hospital, and he wound up designing a system to soften the unit's lighting.
Then the nurses asked him what he could do about sound.
"That's really when I realized that there was no good way out there to measure sound, other than your standard, hand-held meter," he said.
Babies born too soon lose the muffling effect of the womb before their ears can filter sound, White said.
"The sounds ... come from all different directions and all different sources, and they're often associated with unpleasant sensations for the baby," White said.
NICUs are rife with noise pollution created by employees, equipment and excited family members.
"There's no good way for the nurses or doctors to walk up to a parent, tap them on the shoulder and say, 'You're being too loud,"' Smith said. "That's confrontational."
The former car mechanic filled hours of spare time in the evenings and on weekends researching sound standards and building a system.
Smith, who tinkered in radio and TV electronics in high school, hired an acoustical engineer to help. They created a ceiling-mounted system of microphones that picked up sound and funneled data back to a large control panel.
"There was a lot of wiring, a lot of labor, a lot of programming," he said.
St. Vincent paid around $100,000 for the system, which it installed about five years ago. Smith had no interest in shopping his invention to other hospitals because the work took so much time.
Then Riley Hospital, also in Indianapolis, called a few months later.
"They basically said, 'I want that,"' he said.
The latest version of Sonicu can feed a stream of both sound and light data digitally to a computer. It offers the cone-shaped warning lights and can quickly dim the lighting in a room that gets too noisy. It also can make lighting mimic the sun by brightening toward noon and then fading, which also helps babies sleep well.
White, the neonatologist who helped write the national standards, said he knows of no other NICU monitoring system that sophisticated.
Smith has sold systems to a handful of Indiana hospitals, so far to good reviews. He said the systems can cost anywhere from $40,000 to $400,000, depending on each hospital's needs.
The monitors have taught hospital staff to limit the number of groups making rounds at the same time because having more than one group in a room raises noise levels dramatically.
Most NICUs are filled with noise that can't be helped, White said. Fans in the heating and ventilation system have to operate almost constantly, and the monitors need to beep.
The Sonicu system reins in the main noise maker that can be controlled.
"People think, 'Oh gosh, I didn't realize, I'll go over here so I won't have to talk so loud,"' White said. "It really is something that addresses the human factors that we do have some control over."