Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echolocation in bats to see a case in which the voice plays a strictly utilitarian role.

• 并非动物发出的所有声音都充当语言，我们只要把目光转向在蝙蝠身上发现的奇特的回声定位法，就可以从中看到声音确实发挥实际有效的作用。