Click on a date in the calendar above to listen to an archived recording of the previous 24 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. An isolated bright spot in the calendar usually indicates a day of increased background noise due to windy conditions at the sensor site. 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 ×.