The study was led by Rachel Buxton, a biologist at Carleton University in Canada, and published Monday in the scientific journal PNAS.
“We tend to look at the acoustic environment from the point of view of noise pollution and how it disturbs flora and fauna., explained the researcher to AFP. Many of us biologists are very interested in the opposite: what are the benefits of a natural acoustic environment? “
She and her colleagues reviewed the literature on the subject. Most of the past research has been carried out in a laboratory or in a hospital environment, with sounds broadcast to volunteers.
Out of 36 studies, seven looked at the effects on heart rate, blood pressure, pain experienced or stress via cortisol levels.
The others measured the consequences on mood or cognitive performance.
Combining all the positive effects on groups exposed to natural sounds, the researchers noted a 184% improvement in overall health.
These sounds also led to a 28% reduction in stress and annoyance levels.
Among the sounds with the biggest impact: that of water, followed by birdsong, then a mixture of the two.
The research team also analyzed sound recordings in 68 US national parks over the past 15 years, at 221 different locations.
The sounds have been classified: caused by humans, animals, or by the elements (wind, rain, water…). Water and bird sounds could be heard 23% and 42% of the time, respectively.
The parks with the best sound quality (lots of natural sounds, and few sounds caused by humans) were found in Alaska, Hawaii, and the Northwest.
Why this beneficial effect? No one really knows, but the researcher has her hypothesis: “From an evolutionary point of view, an acoustic environment that contains a lot of natural sounds is a good indicator of a safe environment – which allows for psychic rest.” (AFP)