Yellowstone National Park have done a cool thing by releasing a whole library of sounds that were recorded in the National Park into the public domain. The library includes a bunch of biophony including bird and bear calls, and geophony including geysers. You can access the library online at:
https://www.nps.gov/yell/learn/photosmultimedia/soundlibrary.htm
They also have a short video which discusses the National Park Services approach when it comes monitoring sound in the park and the value of that.