Over his long career, Gordon Hempton has mastered the art of truly listening. He’s known as the Sound Tracker. Some people call him an acoustic ecologist. His recordings and books have made him an international expert on the beauty and importance of undisturbed, natural soundscapes — and the ways human beings have changed them. Now, Gordon Hempton is losing his hearing. But with that loss has come an intense urgency to share his life’s work — and his passion — with as many people as are willing to listen.   Twenty Thousand Hertz is produced out of the studios of Defacto Sound, and hosted by Dallas Taylor.  Follow the show on Twitter & Facebook.   Become a monthly contributor at 20k.org/donate.  If you know what this week's mystery sound is, tell us at mystery.20k.org.  Check out the whole Sound Escapes series at BirdNote.org/SoundEscapes, or wherever you get your podcasts.  Check out Gordon’s work and buy recordings on his website soundtracker.com.  Episode transcript, music, and credits can be found here: https://www.20k.org/episodes/soundescapes  Learn more about your ad choices. Visit megaphone.fm/adchoices