By Bryce Gray

With car horns, truck traffic, and the buzz of jackhammers and construction blaring through every city neighborhood, local decibel levels make Chicago one of the noisiest places in the country.

That’s according to data released recently by the National Park Service’s Division of Natural Sounds and Night Skies.

Amid the din, Chicago Wildsounds – an organization of phonographers launched by DePaul University students – has spent the last year and a half studying the area’s natural sounds through localized projects devoted to the emerging field of soundscape ecology.

Birds breaking out in song are a sure clue to soil rich with earthworms, for instance. And crickets change the frequency of their chirps to compete with traffic noise,

Roni Jachowski, a senior environmental studies major and a co-founder of Chicago Wildsounds, says a key goal of the group’s research is “to see if we can make predictions about the health of an ecosystem based on what we hear.”

In the fall, the group put that notion to the test by conducting traditional ecological assessments of soil quality and seeing whether their findings corresponded with sounds above ground.

“We were able to come up with some interesting results,” Jachowski said.

The group found that in areas with greater quantities of earthworms present – a possible indicator of good soil health – there were also more bird calls.  Audio recordings also indicated that fewer birds correlate with higher levels of ammonia in the soil and sparser populations of worms.

[soundcloud url=”https://api.soundcloud.com/playlists/50236462″ params=”auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true” width=”100%” height=”450″ iframe=”true” /]

Another of the group’s main research projects monitors the urban soundscape on a north-south gradient stretching along the lakeshore, from McDonald Woods near the Chicago Botanic Garden in Glencoe to Burnham Wildlife Corridor on the South Side. Jachowski said that the long-term lakefront sound collection is ongoing and findings have yet to be analyzed.

Recordings captured in such an intensely urbanized environment obviously reveal more than simply the sound of the natural world – known as biophony to sound ecologists. Plenty of human-produced sounds – or anthrophony – are picked up along with the natural hum of the wind or thunderstorms, characterized as geophony.

[soundcloud url=”https://api.soundcloud.com/tracks/170249433″ params=”auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true” width=”100%” height=”450″ iframe=”true” /]

Jachowski said that she has been unable to find any location in the Chicago area where the surrounding anthrophony is completely stifled.

“The reason is because of Midway and O’Hare,” said Jachowski. “We have a lot of air noise pollution. That’s what we call a sonic signature and that is Chicago’s sonic signature. It will include airplanes – it just will.”

The students involved with Chicago Wildsounds still have yet to fully analyze their recordings. But other sound ecology researchers have drawn surprising conclusions about the influence of human noise on the natural world.

“There are studies that have shown that crickets are starting to communicate in a different frequency range – in a higher frequency range,” said Jachowski. “And they believe that’s because traffic occupies a low frequency and so crickets are having to operate on a different frequency.”

Bird species, too, have had to alter their vocalizations in order to be heard. For instance, “we know that American robins are communicating louder because of a lot of the anthrophonies – the human-made noises,” said Jachowski, noting that researchers are investigating how noisier environments are impacting reproduction in various species by drowning out mating calls. “Definitely more and more things are starting to come out about how noise is negatively affecting wildlife,” she added.

The effects of noise pollution are not confined to terrestrial ecosystems. In fact, “sounds underwater travel five times farther and it’s a noisy environment,” said Dr. Bryan Pijanowski, a renowned sound ecologist at Purdue University and the featured guest speaker at a Chicago Wildsounds event last Thursday.

“We should be a bit concerned about that because we have a lot of organisms that have to communicate long distances and that’s how they’ve evolved,” Pijanowski said. “Whales, in particular, sing their songs and try to find a mate from long distances away. And if we’re making sounds that hinder that ability, it’s not a good thing.”

Though troubled by the mounting evidence of human-caused noise disturbances in nature, Pijanowski is encouraged by the groundswell of interest in natural sound demonstrated by groups such as Chicago Wildsounds and in the general public.

“Sounds kind of have this special meaning for all of us,” Pijanowski said. “I think for a while there we turned off our ears, and now we’re seeing this resurgence.”