介绍:
And then there is a third filter, it's a biological filter. 还有第三种过滤，是一种生物过滤。
Your cochlea -- it's a part of your inner ear that processes the sound -- is made out of living cells. And those living cells are going to trigger differently according to how often they hear the sound. It's a habituation effect. So because of this, as your voice is the sound you hear the most in your life, you actually hear it less than other sounds. 你的耳蜗——用来处理声音的内耳的一部分——是由活细胞组成的。那些活细胞会根据它们是否频繁地听到某种声音而被不同程度地激发。这是一种习惯效应。因此，你自己的声音虽然是你一生中最常听到的声音，实际上却比其他声音更少的被你的听觉接收。
Finally, we have a fourth filter. It's a neurological filter. Neurologists found out recently that when you open your mouth to create a sound, your own auditory cortex shuts down. So you hear your voice but your brain actually never listens to the sound of your voice. 最后是第四种过滤。这是一种神经过滤。神经学家近期发现当你张开嘴发声的时候，你的听觉皮层会关闭。因此你听到了自己的声音，但是你的大脑并没有去听你的声音。
Well, evolutionarily that might make sense, because we know cognitively what we are going to sound like so maybe we don't need to spend energy analyzing the signal. 按进化论来说，这也说得通，因为我们下意识的知道我们的声音听起来是怎样的，因此我们不需要耗费能量去分析这个信号。
And this is called a corollary discharge and it happens for every motion that your body does. The exact definition of a corollary discharge is a copy of a motor command that is sent by the brain. 这个过程被称作就“伴随发送”，会发生在你身体的每一个动作上。伴随发送的精确定义是一个大脑发出的指令的复印件。
This copy doesn't create any motion itself but instead is sent to other regions of the brain to inform them of the impending motion. And for the voice, this corollary discharge also has a different name. It is your inner voice. 这个复印件自身不产生任何动作，而是被送去大脑的另一个地方通知即将到来的动作。对于声音来说，这个伴随发送也有另一个名字。就是你内心的声音。
So let's recapitulate. We have the mask, the outward voice, the inside of the mask, your inward voice, and then you have your inner voice. And I like to see this one as the puppeteer that holds the strings of the whole system. 同样也使得我们的后脑进化，让我们来概括一下。我们有面具，也就是外在声音，在面具的里面就是你内在的声音，然后就是你内心的声音。我想把这个看成是一个手握整个系统的绳子的演木偶戏的人。
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