Click on a date in the calendar above to listen to an archived recording of the previous – hours of Earth sound. The average (rms) energy recorded each day is represented by the color scale ; the brighter the color, the greater the energy. Audio volumes have been normalized: in recordings containing low energy (dark colors) the audio volume is increased to highlight the Earth's natural background ambience; during energetic periods (bright colors) the volume is reduced to accommodate the powerful signals from large events. Audio is unavailable on days marked ×.