From bird song to bulldozers, sound affects our wellbeing

A new paper from Purdue’s Bryan Pijanowski and colleagues looks at all the ways sound influences human, animal and environmental health

It’s 2 a.m. and you’re woken by a motorcycle revving its engine outside your house. It takes you an hour to get back to sleep, and you wake up exhausted and cranky. Your blood pressure might be a little higher than before, your immunity a little lower.

You’ve just been affected by sound pollution.

We’re all familiar with how air quality affects our health. But too little attention has been given to the health effects of sound. That’s a mistake, says Purdue researcher Bryan Pijanowski, the lead author on a paper on sound and wellbeing in the journal BioScience. The paper takes “a deep dive” on the positives and negatives of our exposure to sound, and what we know in terms of the health impacts,” which parallels the lens of Purdue’s One Health presidential initiative  that involves research at the intersection of human, animal and plant health and well-being.

Exposure to noise – revving motorcycles, the hum of highway traffic, throbbing bass notes leaking out of nightclubs – is associated with higher stress, poor sleep, hypertension, cardiovascular problems, immune dysfunction and more. On the flip side, exposure to nature sounds – birds chirping, waves lapping, the wind rustling autumn leaves – is associated with lower stress, better sleep, lower blood pressure and other health benefits. The benefits are real even if the sound source is not: one study showed that patients in ICUs have lower blood pressure and less agitation when listening to recorded nature sounds on headphones.

A study cited in the paper estimates 1.5 million life years were lost in Europe due to traffic noise alone during a 10-year period. Lower income people are disproportionately affected, as they are more likely to live in noisy areas – near major highways, for example – with fewer quiet green spaces.

The health benefits of sound are something many indigenous communities have long understood, Pijanowski says. A case study in the paper involves research Pijanowski conducted in Mongolia among indigenous nomadic herders. These herders are experts in listening to nature, Pijanowski says. When he asked one herder where to find the best nature sounds to record with his sensors, the man directed him to his “energy giving site.” This was a place he went to relax and reconnect with nature, listening to the song of the cuckoo and the deer bugling in the morning. It was the same place his father and grandfather had gone before him, a place where he would one day take his own children.

There are a lot of indigenous communities that are so close to nature they have somewhere to go where they can heal, that gives them energy again,” Pijanowski says.

The health impacts of sound extend to non-human animals. Pijanowski’s literature review showed wildlife exposed to high levels of noise had higher levels of cardiovascular disease and other health problems. This has potential knock-on effects for humans – if birds, for example, flee unpleasantly noisy environments, there’s less soothing birdsong for humans, which in turn makes humans sicker.

A lack of nature sounds can also be a marker of a sick environment. Pijanowski’s paper considers a study looking at a former nuclear weapons production facility in Georgia, which still has a high level of radioactive contamination. A group of researchers at the University of Georgia used sonic monitors to compare the site with another, non-contaminated site, and found that the former weapons production facility had fewer insect and animal sounds. This, again, means humans in the area have a less healthy sonic environment. It’s all connected.

But while we have established thresholds for air pollution – anyone can look at their phone’s weather app to see real-time air quality levels – nothing similar exists for sound pollution. We need more research to figure out the thresholds where a given environment goes from healthy to unhealthy, says Pijanowski.

“If you want to think about sound and a healthy planet, then what we need is a bunch of experts who can be responsive to the problem,” Pijanowski says.

This could include transportation experts – highways and airports are particularly bad noise polluters – as well as wildlife researchers and experts in the auditory system.

The paper’s authors include several of Pijanowski’s colleagues in Purdue’s Center for Global Soundscapes, Department of Music and Department of Speech, Language and Hearing Sciences, as well as researchers at the University of Georgia, the University of Arizona, University College London and Universitas Ciputra in Indonesia.

Pijanowski admits that controlling or regulating noise is especially tricky. While air pollution often has an identifiable culprit – such as a dirty factory– noise comes from all around. As to why certain sounds are healthy while others are harmful, it may have something to do with evolution, Pijanowski says.

“Natural sounds are ones we can process easily without stress; we understand what their sources are, what there meaning is, and so they have a calming effect,” Pijanowski says. “Whereas the sounds of urban environments, we haven’t evolved with those sounds, so our mind takes a lot of energy to process that information.”

To get the health benefits of nature sounds, Pijanowski suggests a walk in the woods is a good place to start.

 “Build a personal experience and see – does this make me feel good? Does this make me more clear-headed?”