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Hey there! Welcome to Life Noggin!
大家好！欢迎收看脑洞大开的生命奇想！
Sound is a beautiful thing.
声音是一种美丽的东西。
It's what allows us to listen to music, communicate verbal language, and hear birds chirping on a summer morning.
它让我们能够聆听音乐，交谈，在夏日的早晨听到鸟儿啁啾。
I love all of those things, except the birds because they wake me up.
我喜欢这些，除了鸟，因为它们把我吵醒了。
But how are we able to hear all that?
但是我们怎么能听到这些呢?
What is it about our ears that allows us to hear?
我们的耳朵有什么可以让我们听得到呢?
To answer that, first we need to discuss the physics of a sound wave.
要回答这个问题，首先我们需要讨论声波的物理性质。
These are longitudinal waves that travel through a medium.
这是通过介质传播的纵波。
And therefore, there is no sound in a vacuum like space.
因此，真空中，比如太空中，没有声音。
Sorry Star Wars.
对不起《星球大战》。
But, simply put, sound waves are variations of pressure caused by some type of vibration, like an oscillating violin string or the vocal folds that vibrate as you speak.
但是，简单地说，声波是由某种振动引起的压力的变化，比如小提琴弦的振动或者你说话时声带的振动。
These pressure variations can be modeled by a sine wave, where the peaks represent increased pressure and the troughs represent decreased pressure.
这些压力变化可以用正弦波来模拟，峰代表压力增加，而谷代表压力减小。
To visualize that, let's think of a slinky: if you and your friend hold the ends and you move your hand back and forth,
为了让这个问题更直观一点，我们想象一下螺旋弹簧：你和你的朋友各执一端，你来回摆动手，
the areas where the slinky is compressed represent areas of increased pressure called compressions,
弹簧被压缩的地方代表受到压力增加的区域，称为压缩，
and the areas where the slinky is stretched represent areas of decreased pressure called rarefactions.
弹簧被拉伸的地方代表受到压力减小的区域，称为稀疏。
A few important aspects of this wave include the frequency and the amplitude.
这个波的几个重要特性包括频率和振幅。
Looking at this sine wave, the frequency is defined as how many wavelengths, or complete cycles, pass a specific point in one second.
看这个正弦波，频率的定义是在一秒内有多少波长或完整周期通过一个特定的点。
And this value is eventually perceived as pitch, with 20 hertz as the lowest humans can hear and 20 kilohertz as the highest.
这个值也就是音高，20赫兹是人能听到的最低值，20千赫兹是最高值。
The amplitude of the wave, measured as how the air pressure deviates from equilibrium, determines the sound wave's intensity, which is eventually perceived as the sound's loudness.
波的振幅，是指气压偏离平衡，它决定声波的强度，也就是声音的响度。
And this is usually represented by the nonlinear decibel scale, where a normal conversation is around 60 decibels and a rock concert is around 120 decibels.
这通常是由非线性分贝表来表示的，正常的谈话大约是60分贝，而摇滚音乐会的音量大约是120分贝。
But for all of you rock fans, keep in mind that the threshold of pain occurs around 130 decibels.
但所有的摇滚爱好者，请记住，疼痛的阈值在130分贝左右。
You definitely don't wanna get too much higher than that.
你肯定不会想要听到比这更高的声音。
But anyway, now that we know all of this, we can finally move on to what happens in the ear.
不过，既然我们已经知道了这些，我们终于可以往下讨论耳朵里的事情了。
Let's begin with the part we see, called the pinna.
我们从能看到的那部分开始，也就是耳廓。
It collects the sound waves and sends it into the ear canal where the sound is amplified.
它收集声波并将其送入耳道，声音在耳道里被放大。
And fun fact: this is where ear wax forms, coating the ear canal to moisturize it, fight off infection, and help keep debris from getting into your inner ear.
有趣的是，这是耳垢形成的地方，覆盖耳道的耳垢可以滋润耳道，防止感染，防止碎片进入内耳。
And if you're Shrek, it also allows you to make candles...Gross.
如果你是史莱克，你还能用它做蜡烛……真恶心。
But once the sound wave passes through the ear canal, it reaches your eardrum, or tympanic membrane.
声波穿过耳道，就会到达你的耳膜或鼓膜。
This transfers the wave's vibrations through the tiny bones called the ossicles, eventually reaching the inner ear.
它通过小骨这样的微小骨骼传递波的震动，最终到达内耳。
From here, we have two main structures: the semicircular canals, which are in charge of balance, and the cochlea, which is what we really care about.
这里，我们有两个主要的结构：负责平衡的半规管，还有耳蜗，这是我们真正关心的。
See, this is essentially your body's microphone, converting sound pressure waves into electrical impulses that are eventually sent to the auditory nerve and then to the brain.
看，这是你身体里的麦克风，把声音的压力波转换成电脉冲，最终传送到听觉神经，然后传送到大脑。
And this transition occurs in the Organ of Corti, which sounds way too royal to be a body part.
这种转变发生在螺旋器中，这听起来太显贵了，好像不是身体的一部分。
Anyway, this sits on top of the basilar membrane and contains up to 20,000 tiny hair cells.
它位于基底膜的顶部，包含了多达20,000个小毛细胞。
And the place among this membrane where the most hair cells are excited determines the pitch of the sound.
基底膜中这个地方兴奋毛细胞最多，这里决定了声音的音高。
Lastly, as the signals pass through the auditory nerve, they reach various areas of the brain like the auditory cortex, and voila, you can hear!
最后，当信号穿过听觉神经，它们到达大脑的各个区域，比如听觉皮层，然后，你听到声音啦!
Don't forget to come back every Monday for a brand new video.
每周一都要回来看新视频哦！
As always, I'm Blocko, this has been Life Noggin.
我是宝高，这里是脑洞大开的生命奇想。
Don't forget to keep on thinking!
思考不要停！
