How loud is the U. S.*? Researchers from the National Park Service, led by Kurt Fristrup, shared these sound maps at a conference on Monday.

Ten years ago, Fristrup set out to measure an important natural resource – the amount of silence in national parks. He eventually realized it would take forever to actually make recordings throughout all the parks, so he used a computer program to model loudness across the country.

He uploaded all the audio he already had (over a million hours of sound from 546 recording sites) along with environmental data – proximity to roads, the type of vegetation, any nearby topographical features that might act as sound barriers etc. The computer “learned” how all these factors interacted to create a specific sound level, and then predicted loudness everywhere.

The map of all sound roughly follows population density, though there are many uninhabited places that are still loud because they are near major roads or airplane routes.

Far more interesting to me is the map of natural sounds. What happens when you subtract all of humanity’s noise? You are left with rushing rivers, crashing waves, wind in trees … and in the mountain desert, near silence.

A lot of natural soundscapes have been severely degraded, but Fristrup told me there is a more important takeaway from this kind of research: there are lots of things we can do to decrease noise pollution in nature and in our communities.

Images: Dan Mennitt, Kurt Fristrup – National Park Service

*with apologies to Alaska and Hawaii

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