The feeling of exhaustion that so often hits at the end of a workday might be the result of an early morning, a string of bad meetings or maybe a lack of caffeine.

An equally likely culprit, though, is the barrage of sounds we’re exposed to each day, including ambient noise most people don’t even notice. Those hidden sounds, experts warn, could be having a big impact on your well-being.

“Hearing is primal. You don't have ear lids. There is no way to turn it off. You hear everything around you all day, all the time,” says Julian Treasure, founder The Sound Agency, an audio branding firm based in the U.K.

“The world is increasingly noisy. Most of us have to deal with traffic, construction, aircraft, neighbour noise, whatever it may be. The effect of this is sort of numbing. We’ve become very unconscious of sound. But it affects us powerfully under the radar.”

That is in part due to the complex nature of the human auditory system, one of the first fully formed systems in the human body. When a sound first enters the ear, the body begins processing it on a subconscious level. As the wave progresses through the brain, it is processed by a number of increasingly sophisticated “weigh stations,” says Phil Gander, a research scientist at the University of Iowa who studies how the brain makes sense of sound.

These so-called weigh stations range from the undetectable to others that ignite fight-or-flight responses, trigger memories, evoke emotions and cue other physiological reactions.

“If you hear the voice of someone you’re madly in love with, your body reacts hormonally. If you are exposed to scary sounds, you’re going to be come very stressed out,” says Marsha Johnson, an Oregon audiologist who specializes in treating patients with complex hearing conditions including tinnitus and hyperacusis. “When we get stressed out, our immune system suffers.”

Sounds that induce stress include noise pollution caused by airplanes or traffic or even a constantly running TV. But low-frequency noise — the ambient sounds one might encounter in an open-concept office without much notice — can also quietly grind down our energy stores.

“After a while, people report feeling more physically tired and mentally wiped out or even feeling depressed,” says Paul Madaule, a therapist who founded The Listening Centre in Toronto more than 40 years ago. “This can have an effect on their mental state and it can also affect sleep.”

Treasure, the soundscape designer, said productivity could be decreased by up to 65 per cent in open-plan offices due to noise alone.

"Music is the best thing we have to compensate for the noisy world in which we live in"

— Paul Madaule, therapist and founder of The Listening Centre in Toronto

“It’s rubbish for concentration,” Treasure says. “We have the mental bandwidth for 1.6 human conversations at a time, meaning you can’t understand two people talking at once. If someone in the office is behind you talking, they’re taking up half your bandwidth. And you need to hear the voice in your head to write or do mathematics or whatever it may be.”

To regain some of that bandwidth (and to improve moods at the office), Treasure’s company, which designs “soundscapes” for retail and office environments, recommends the use of sound as a positive influence.

Research, including several studies done at the University of Surrey, connects exposure to the sounds of wind, water and birdsong to decreased stress. Treasure tells many of his clients pipe these sounds into the workplace.

“We use birdsong a great deal because it makes most people feel secure. We’ve learned over hundreds of thousands of years that when the birds are happily tweeting, things are normally quite safe,” he says. “It is also nature’s alarm clock — time to be awake and alert. For working, birds are very good.”

In Toronto, Madaule’s therapy sessions focus on training people not to simply try to block out unwanted sounds. While earplugs are suitable on occasion, he says prolonged use can cause more damage.

Madaule prefers instead to teach people how to refine their listening, a skill that includes learning how to protect their brains from being taxed by the task of interpreting unwanted sounds.

When Madaule assigns homework, it often involves listening to music (he likes Mozart or sounds of the cello), which he calls “vitamins for the brain.”

“Music is the best thing we have to compensate for the noisy world in which we live in,” he says.

Johnson, the Oregon audiologist, coaches her patients to include “sound as therapy for your brain” in each day for a variety of health benefits.

“If you’re willing to listen to new types of music or sounds, it will actually form new neural connections in your central nervous system,” she says. “Maybe you learn a new language. Maybe you’re a country fan but you try a little classical. It has been shown that when you listen to pleasant sounds, it actually lowers your blood pressure. Use sound as your friend.”

Johnson believes the auditory system deserves more respect and care than most of us pay it.

“We tend to use our ears like the bottoms of our feet,” she says. “We don’t think of them unless we have a problem.”