PARIS: Samuel Challeat was riding his bike in the city of Toulouse in the hours before France’s strict Covid-19 lockdown took hold when the thought came to him.

What impact will confinement have on the urban sound environment, and how could it be measured, he wondered.

That same day, Challeat, a geographer at the University of Toulouse II, launched an appeal to scientists and researchers around the world to measure the “unique perturbation” of city sounds during confinement.

The project, called Silent Cities, was up and running within 48 hours, and now has more than 350 participants in 40 countries around the world, including France, the United States, India and Brazil, Challeat said in an interview.

Participants captured ambient sound — recording one out of every 10 minutes — and uploading the data into an open-source database.

Because the project is open-source, anyone can access the data and the sound files for free.

The World Health Organisation (WHO) has tagged noise pollution as the second most dangerous environmental risk factor for humans after air pollution.

One in five Europeans is exposed to long-term noise pollution that is harmful to health, according to the European Environment Agency.

Confinement was the perfect natural experiment for establishing a baseline for noise pollution in cities, according to Jerome Sueur, a bioacoustician at Paris’s natural history museum.

“It showed us to what extent we are in a noisy environment and allows us to quantify that,” he said.

Sueur set up sound measurement instruments called magnetometers in Paris and Cachan, the suburb where he lives, as part of the Silent Cities project.

Published in Dawn, July 4th, 2020