The ideal amount is about 50 decibels, comparable to moderate rain or birdsong.
“Everybody knows that loud noise is stressful, and, in fact, extremely loud noise is harmful to your ear,” says study coauthor Esther Sternberg, director of the University of Arizona Institute on Place, Wellbeing & Performance. “But what was new about this is that with even low levels of sound—less than 50 decibels—the stress response is higher.”
The study’s findings suggest that if employers intend to build or redesign their office spaces with employee health and well-being in mind, they might want to consult acoustical engineers who can help them dial in conditions for good environmental sound, says Sternberg.
The study appears in the journal Nature Digital Medicine. Sudha Ram, professor of management information systems in the Eller College of Management, is the study’s senior author. Karthik Srinivasan, an assistant professor at the University of Kansas, led the research when he was a doctoral student at Eller, and is the paper’s lead author.
“When we think about well-being, typically we think about emotional or mental well-being,” Srinivasan says. “We hardly ever consider the physiological well-being or the actual ‘what’s happening in our body,’ which is also important to understand when we’re continuously exposed to environmental factors such as sound.”
A study Sternberg led in 2018 showed employees who worked in open office seating—at desks that aren’t separated by partitions—had greater daytime activity levels and lower stress levels in the evening, after work hours, compared to workers in private offices and cubicles.
But open office spaces also come with a common complaint from people who work in them: noise. With this latest study, Sternberg and her coauthors shed more light on employees’ physiological reactions to office sound.
The new study was part of Sternberg’s larger research project, called Wellbuilt for Wellbeing, in partnership with the US General Services Administration, the federal agency that oversees basic operations for all nonmilitary federal government buildings, including building and buying real estate, managing buildings’ operating systems, and managing government-wide reentry into the workplace amid the COVID-19 pandemic.
To measure the impact of sound on office workers, researchers asked 231 of the agency’s employees working in four buildings across the US to wear two devices for three days. One device, worn around the neck, measured sound levels in the person’s work environment.
Another, worn on the chest, measured participants’ physiological stress and relaxation levels, using heart rate variability, or the varying lengths of time between each heartbeat. The chest-worn monitors were designed by Aclima, Inc., which also contributed to the study.
Heart rate variability is a direct result of breathing, Sternberg says: As a person inhales, his or her heart rate slightly increases, and it decreases as the person exhales, causing variability between heartbeats.
The more variable the space between heartbeats, the healthier the person is.
“One way to think of it is, the least-variable heart rhythm is a straight line,” Sternberg says, referring to a flatline on an electrocardiogram—a sign someone has died. “You don’t want that—you want a variable heart rate.”
The researchers measured heart rate variability alongside environmental sound, then used mathematical modeling to determine how changing sound levels affect a person’s physiological well-being.
Participants also answered questions sent to their smartphones about how they were feeling at random times throughout the day.
The results show that when a worker’s environmental sound level was above 50 decibels, each 10-decibel increase was related to a 1.9% decrease in physiological well-being. But when office sound was lower than 50 decibels, each 10-decibel increase related to a 5.4% increase in physiological well-being.
Humans’ tendency to get distracted, Sternberg says, is a result of the brain’s stress response to potential threats. Our brains are “difference detectors” that take note of sudden changes in sounds so we can decide to fight or flee, she said.
That may explain why low, steady sounds help mask distractions in the workplace, she adds.
“People are always working in coffee shops—those are not quiet spaces. But the reason you can concentrate there is because the sounds all merge to become background noise,” Sternberg says. “It masks sound that might be distracting. If you hear a pin drop when it’s very, very quiet, it will distract you from what you’re doing.”
The study, Sternberg says, offers precise data that can guide employers in designing office spaces to maximize employee well-being. Acoustical engineers already take great care in choosing or designing furniture, flooring, wall coverings, and other aspects of spaces such as concert halls, recording studios, and museums.
If employee health is a priority, Sternberg says, “There’s no reason why these simple interventions can’t be installed in office spaces to mitigate sound distraction.”
Source: University of Arizona, Jon Niccum for University of Kansas
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