No really! This is the sound of a cottonwood tree, captured by composer and bio-acoustician Bernie Krause. While out recording the sounds of bats he picked up a peculiar signal, which got stronger nearer a cottonwood tree. After drilling a small hole and inserting a microphone Krause managed to record the high frequency signal. What you can hear has been slowed down to get it within human hearing range. Apparently the noise occurs when cells in the tree pop while trying to maintain pressure during a drought. However, I can’t get the image of tap dancing wood nymphs out of my head! I’ll leave you to decide which explanation you prefer…

via: http://www.emusician.com/