The healthiest noise level for the office is around 50 decibels

Research shows that too much or too little noise in the office can be detrimental to our well-being.

About 50 decibels is ideal, comparable to moderate rain or birdsong.

“Everyone 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 University of Arizona Institute on Place, Wellbeing & Performance. “But what was new was that even at low sound levels – less than 50 decibels – the stress response is higher.”

The study’s findings suggest that if employers want to build or remodel their office space with employee health and well-being in mind, they may want to consult acoustics engineers who can help them create conditions for good ambient sound, says Sternberg.

The study appears in the journal Nature Digital Medicine. Sudha Ram, Professor of Management Information Systems at Eller College of Management, is the senior author of the study. Karthik Srinivasan, an assistant professor at the University of Kansas, led the research when he was a graduate student with Eller and is the lead author of the paper.

“When we think of well-being, we usually think of emotional or mental well-being,” says Srinivasan. “We hardly consider physiological well-being or actual ‘what’s happening inside our bodies,’ which is also important to understand when we’re constantly exposed to environmental factors like noise.”

A study conducted by Sternberg in 2018 showed that employees who worked in open offices — at desks that weren’t separated by partitions — had more activity during the day and less stress in the evening after work than employees in individual 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 responses to office noise.

The new study was part of Sternberg’s larger research project called Wellbuilt for Wellbeing in collaboration with the US General Services Administration, the federal agency that oversees the basic operations of all non-military government buildings, including the construction and purchase of real estate and the management of building operations systems and administration of the government-wide return to work amid the COVID-19 pandemic.

To measure the effects of noise on office workers, researchers asked 231 agency employees working in four buildings across the US to wear two devices for three days. A device worn around the neck measured sound levels in the person’s work environment.

Another chest-worn device measured participants’ physiological levels of stress and relaxation based on heart rate variability, or the difference in time between heartbeats. The chest-worn monitors were developed by Aclima, Inc., which also contributed to the study.

According to Sternberg, heart rate variability is a direct result of breathing: When a person breathes in, their heart rate increases slightly and it decreases when the person breathes out, resulting in variability between heartbeats.

The more variable the interval between heartbeats, the healthier the person.

“You can think of it like this, the least variable heart rhythm is a straight line,” Sternberg says, referring to a flat line on an electrocardiogram — a sign someone has died. “You don’t want that — you want a variable heart rate.”

Researchers measured heart rate variability along with ambient noise, then used mathematical models 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 ambient noise level was above 50 decibels, every 10 decibel increase was associated with a 1.9% decrease in physiological well-being. But when office noise was below 50 decibels, every 10 decibel increase meant a 5.4% increase in physiological well-being.

According to Sternberg, people’s tendency to become distracted is a result of the brain’s stress response to potential threats. Our brains are “difference detectors” that notice sudden changes in sounds so we can choose to fight or flee, she said.

That might explain why quiet, steady noise helps mask distractions in the workplace, she adds.

“People always work in cafes – these are not quiet places. But the reason you can focus there is because the sounds all blend into background noise,” says Sternberg. “It masks sounds that might be distracting. If you hear a pin drop while it’s very, very quiet, it distracts you from what you’re doing.”

According to Sternberg, the study provides accurate data that employers can use to guide how office spaces are designed to maximize employee well-being. Acoustic engineers already take great care in selecting 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 reduce noise distraction.”

Source: University of Arizona, Jon Niccum for the University of Kansas

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