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An international group of researchers collected one hundred years' worth of sounds from around the world to investigate how soundscapes differ between urban and natural environments. They also examined how these soundscapes change throughout the day and throughout the year. The research, in Nature Ecology & Evolution, revealed that soundscape rhythms are less predictable for people living in urban areas than for animals in the wild.

In addition to researchers from the universities of Jyväskylä and Helsinki, the international study involved researchers from over thirty countries. Samples were collected by automatic recorders from 139 locations over several years.

From the collected audio material, researchers analyzed various descriptive indicators. For example, they examined the amount of sound energy present in low and high frequencies, as well as the variation in the sounds. The sounds were also classified into different categories, including human speech, vehicle sounds, and natural sounds such as rain and wind. Bird species were also automatically identified based on the sounds they produce.

"The collected sound data provides evidence of predictable rhythms in nature," says University Researcher Panu Somervuo from the University of Helsinki. "For example, birds sing most actively in the morning and evening as well as in spring."

Birds are an important part of urban green spaces

One of the most surprising findings of this study was that the number of bird species in urban green areas was, on average, greater than in natural environments.

"Green areas are often highly diverse, so a one-hectare monitoring plot can serve as a habitat for several bird species," says Academy Professor Otso Ovaskainen from the University of Jyväskylä. "However, this does not mean that natural areas in their original state are unimportant to birds, since species living there cannot be found in urban areas."