Less aircraft noise, fewer buses, fewer cars: Between March and November 2020, the effects of the first two lockdowns were particularly noticeable acoustically. During this time, 261 bioacousticians from 35 countries decided to start one of the most extensive audio documentation projects in history. “We all set up our devices together, hung them out and documented how human noise suddenly became quieter,” says Lower Austrian bioacoustician Robin Sandfort.
At home in Groß-Enzersdorf (Gänserndorf district), Sandfort hung his recording device on the balcony. Sound data from Lower Austria, along with recordings from Tokyo, New York and Rio de Janeiro, are now part of the extensive sound dataset that preserved the listening experience during the pandemic. Except for Antarctica, it contains audio samples from all continents.
Because the Covid-19 measures were different in every city, the scientists were also able to document subtle nuances between noise reduction and natural background noise. The results of the study have now been published in the journal “Scientific Data”.
Birds did not have to “shout out” human noise
Birds reacted particularly clearly to the changes in the background noise, says Sandfort. Another reason was that birds did not sing louder to fill the silence. “The exact opposite was the case,” the bioacoustician told noe.ORF.at: “They no longer have to shout over the human noise.”
Birds would only sing as loudly as necessary to drown out the noise. “They have to be louder than the bus, louder than the screeching brakes,” explains Sandfort: “And when this human noise was gone, the birds sang more quietly, with more nuance, in different frequencies than they do in normal everyday life.” A study from San Francisco came to similar results – read more in Silence made birds sing more beautifully (science.ORF.at; 25.9.2020).
AI removed human language
The 260 researchers now want to publish the data set created over two years, including all raw data, but cleaned of human conversations. “We all hung it up on our private balconies. “Data protection is of course a very important issue,” explains Sandfort.
All human frequencies were removed using artificial intelligence (AI). The extensive data set will allow other scientists to research completely new questions using the collected data in the future.
