美国科学60秒 SSS 2013-06-12（在线收听）

　　The human voice is capable of forming a plethora of incredibly different sounds. So many, in fact, that each individual language contains only a subset of potential sound units or phonemes. What factors determine whether a phoneme enters coming in use or relegated to silence? It turns out geography may play a role. One phoneme that occurs in only 20 percent of the world's languages is the ejective consonance such as Aah or KAh.  Caleb Elvin, an anthropologist at the University of Miami, decided to map where the sound occurs. He took a sample of 567 languages spoken around the world and compares the locations and the attitudes of those either contained or ignored the ejective consonance. Elvin discovered that languages that includes the ejective consonance will generally spoken at a higher elevation than those that not. His research is in the journal of Plos One. Elvin suggests that sounds are more popular at the altitude because lower air pressure may make it easier to produce the burst of air that is the key characteristic of ejective consonance which is Pretty Cool.