By Kyle Mittan, University Communications
Choosing to work in the murmur of a busy coffee shop rather than in an office with library-level silence might be healthier, according to a new study by researchers at the University of Arizona and University of Kansas.
The study finds—perhaps unsurprisingly—that loud noises at the office have a negative impact on employee wellbeing. But the study also suggests that complete silence is not conducive to a healthy workplace.
The sweet spot for office noise? About 50 decibels, roughly equivalent to birdsong or the pitter-patter of moderate rain.
"Everybody knows that loud noise is stressful, and, in fact, extremely loud noise is harmful to your ear," says study co-author Esther Sternberg, director of the UArizona Institute on Place, Wellbeing and 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, part of a larger workplace wellbeing research project led by Sternberg, suggests that if employers intend to build or redesign their office spaces with employee health and wellbeing in mind, they might want to consult acoustical engineers who can help them dial in conditions for good environmental sound, says Sternberg, who is also director of research for the UArizona Andrew Weil Center for Integrative Medicine and a member of the university's BIO5 Institute.
The study was published earlier this month 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 wellbeing, typically we think about emotional or mental wellbeing," Srinivasan says. "We hardly ever consider the physiological wellbeing 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."
Sternberg, who also holds a joint appointment in the College of Architecture, Planning and Landscape Architecture, is a renowned expert on the ways workspaces can influence physical and mental health. A study she 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 co-authors 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 U.S. 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 U.S. 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 partnered on 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 wellbeing.
Participants also answered questions sent to their smartphones about how they were feeling at random times throughout the day.
The results showed 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 wellbeing. But when office sound was lower than 50 decibels, each 10-decibel increase related to a 5.4% increase in physiological wellbeing.
Humans' tendency to get distracted, Sternberg said, 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 says.
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 wellbeing. 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."
Jon Niccum, public affairs officer at the University of Kansas, contributed to this article.