There are over 70 languages in the world with just whistled sounds. They are spread around the world, from The French Pyrenees, the Canary Islands, Turkey, the foothills of the Himalayas, and the Amazon Basin.
They are usually used in areas where there are hills and valleys, or forests, where the normal human speech does not spread readily.
The following articles explore more this fascinating topic:
- BBC Future: The Beautiful Languages Of The People Who Talk Like Birds.
- The Fascinating Art of Whistled Speech by Julien Meyer, a linguist and bio-acoustician who researches the topic of whistled languages.
- Le Monde Siffle - The Whistled World.