Whale songs are used by certain species of whales to communicate and socialize. It is characterized as a composition of clicks, whistles and pulses that can last anywhere from 6 to 35 minutes. Some whales have been known to sing for as long as 22 hours. These songs are usually bellow 4 kHz and sometime inaudible to human ears. Recently, a unique whale song was recorded in the western Indian Ocean and it has led to the conclusion that a previously undefined population of blue whales in the region.