I do believe that the most endangered sound in this world is silence. Even in the dead of night, I can hear the buzzing of insects outside or the gush of air through the AC vent inside. If I isolate myself deep in the forest, I can still hear the birds chirping or the river flowing nearby. When the teacher asks for “pin drop” silence, you can still hear a few chuckles in the class room. Or perhaps the sound of your own breath. If you sleep off, your vivid dreams will show you people talking and making merry.