I was doing some research into the work of Bernie Krause when I stumbled across this intriguing wee clip taken from a lecture given by the man himself. Krause explains how after using a hydrophone with the ability to detect frequencies higher than we are able to hear to record from the inside of a tree trunk, he pitched the recording down seven octaves to reveal the bizarre rhythmic pulse.
It really makes one wonder what else out there is making interesting sounds that are beyond our hearing range and and on a similar note, when do we get implants that allow us to hear them? Imagine a 100,000Hz soundwalk.
Also, check out this man-made singing tree.