This is Scientific American's 60-second Science, I'm ―Jason Goldman.In the shadow of Huangshan Mountain in southeastern China lives a beige frog with black stripes.The concave-eared torrent frog, or Odorrana tormota, gets its name from its unusual hearing apparatus."It has kind of an ear canal-like structure like humans, and like most mammals.For most frog species, the eardrums are located on the body's surface, on the lateral part of the body surface.But here the eardrum is invisible because it is embedded deep inside the head, in the skull."Biologist Albert Feng, from the University of Illinois at Urbana-Champaign.Back in 2006, Feng and his colleagues discovered that this unusual anatomy allows the frogs to hear ultrasound, which includes frequencies greater than 20 Kilohertz.Biologists had always assumed that ability was restricted to some mammals because it was only known in bats, whales, dolphins, and some rodents.We can’t hear in that range.The streams that the frogs live in are quite noisy, but most of those sounds are low frequency.By restricting their vocalizations to the higher frequencies, including ultrasound, the frogs are better able to hear each other."The higher the frequency, the less that signal is distorted, or at least masked, by the ambient noise."
这里是科学美国人――60秒科学系列，我是杰森・戈德曼。在中国东南部的黄山背光处，生活着一种带有黑色条纹的浅褐色青蛙。凹耳洪流蛙(Odorrana tormota)，因其不同寻常的听觉器官而得名。“它像人类和大多数哺乳动物一样有一种类似耳道的结构。对于大多数蛙类来说，耳膜位于身体表面，在身体表面的侧面。但凹耳洪流蛙，耳膜是看不见的，因为它深嵌在头部的头骨中。”来自伊利诺伊大学香槟分校的生物学家阿尔伯特・冯说。早在2006年，阿尔伯特・冯和他的同事就发现，这种不同寻常的解剖结构使青蛙能够听到超声波，其中包括频率超过20千赫兹的超声波。生物学家一直认为这种能力仅限于一些哺乳动物，因为只知道蝙蝠、鲸鱼、海豚和一些啮齿动物有这种能力。我们听不见那个范围的声音。青蛙生活的河流非常吵闹，但大多数声音的频率都很低。通过将它们的叫声限制在更高的频率，包括超声波，青蛙们能更好地听到彼此的叫声。“频率越高，环境噪声影响下的信号失真越少或至少信号被掩盖得越少。”
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