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Are the sounds of throat clearing, construction, or the clack-clack-clack of computer keyboards making you scream inside?
清嗓子的声音，建筑施工的声音，敲键盘的声音，这些声音会让你内心抓狂吗？
Before you commit a serious crime, let’s talk about some OTHER solutions, like noise-canceling headphones.
在你因为这些噪音犯下严重罪行之前，我们不妨先聊聊其他解决办法，比如……降噪耳机。
And specifically, how do they work to drown all those terrible noises?
以及它们究竟是怎么盖住那些超级讨人嫌的噪音的？
The first patent for noise cancellation showed up as early as the 1930’s,
第一项专注于消除噪音的专利早在20世纪30年代就出现了，
though it wasn’t until 1986 when the technology made its big debut
尽管这项技术首次风光亮相已经是1986年
when two pilots took flight in the Voyager aircraft for a non-stop trip around the world.
两名飞行员乘坐“旅行者”飞机开启一站式环游世界之旅的时候的事了。
The ultra-lightweight cockpit design wasn’t insulated and sat directly above the engine, which needless to say, was very loud.
由于超轻的“旅行者”驾驶舱没有隔热设计，飞行员的座椅恰好又在发动机的正上方，不用说，那噪音肯定是相当的大。
Bose provided a prototype device to dampen the sound.
于是，博士为他们设计了一款降噪设备的原型产品。
Soon after, the aviation industry, the military, and eventually consumers began to adopt noise cancellation technology.
不久之后，航空业、军队乃至消费者都开始采用噪音消除技术了。
To understand how this tech works, we need a little primer on the physics of sound.
要了解这项技术的工作原理，我们得先聊点儿声音物理学的基本常识。
Sound waves, or pressure waves, are essentially just the mechanical vibrations of particles moving through a medium—like air which can consist of varying densities.
声波，或者说压力波，本质上只是粒子在介质——比如空气，而空气的密度也是有变化的——中发生偏离所引起的机械振动。
As the particles react to these waves, they compress air together,
粒子受到声波的扰动就会一起挤压周围的空气，
and then expand back out again, producing a series of peaks and troughs.
随后继续向后传播，产生一系列的波峰和波谷。
Depending on the density of the medium that they’re traveling through,
传递声波的介质的密度不同，
the distance between each point of high and low pressure can vary, which is what we call amplitude.
每个高压点和低压点之间的距离，也就是我们所说的振幅就会不同，
The amount of time between each period of compression and expansion is what’s known as frequency, otherwise known as pitch.
每个压缩和扩张周期的时间量称为频率，也称音调。
Most noise-canceling makes use of two technologies, and the first is pretty low tech.
大多数降噪设备都用到了两种技术，其中一种并没有什么技术含量。
Known as “passive noise cancellation,” it’s about as complicated as putting your hands over your ears to create a tight seal.
这种就是所谓的“被动降噪”技术，“复杂”程度嘛，就跟用手捂住耳朵以形成一道密封墙差不多一个级别。
Headphones can be molded into specific shapes and include sound-absorbing materials,
我们的（头戴式）耳机可以做成各种特定的性状，内部还可以填充高密度泡沫或耳塞之类
like high-density foam or earbuds, that partially block sound waves.
能够阻隔部分声波的吸声材料。
Something as simple as an earbud that fits snugly into your ear canal is another example of the tech that’s often marketed as “noise isolating”.
这种技术经常被冠上“隔音”的名头，耳塞式耳机这种可以轻松塞进你耳道的产品则是普通的头戴式耳机之外的另一个例子。
Getting a good seal can be a challenge, however—since everyone’s ears are different and not all headphones fit equally well.
不过，要想获得较好的密封效果并不容易，因为每个人的耳朵都不一样，并非所有耳塞式耳机都能很好地贴合每个人的耳朵。
The second technology is active noise canceling.
另一种降噪技术便是“主动降噪”技术。
Microphones built into the headphones detect ambient sounds and convert them into an electrical signal.
耳机内置的麦克风可以检测周围环境的声音并将其转换为电信号。
The new sound wave is flipped, and is known as an antiphase.
新产生的声波是原来的声波翻转后，也即“反相”后的形态。
When the two waves combine near the listener’s ear, the opposing sound waves cancel each other out.
两个波到达听者耳朵之前会出现重叠，彼此抵消一部分能量。
Known as destructive interference, the result is near silence,
这就是所谓的“相消干涉”，干涉的结果便是接近静音的状态，
allowing you to immerse yourself in a favorite tune or just hear yourself think!
这样一来，你就能沉浸在你喜欢的音乐当中，或安静思考了！
But this technology is not perfect.
只不过，目前这种技术还没有达到尽善尽美的地步。
That’s because the microphone and antiphase-producing speakers aren’t exactly in the same location.
这是因为麦克风和产生反相声波的扬声器的位置并不完全重叠。
The antiphase isn’t a perfect inversion of the actual sound.
反相声波和原声波并不是百分百反相的。
So instead of hearing no airplane engine, you hear muffled airplane engine.
所以，飞行员完全听不到一丁点儿引擎的声音是不可能的，只不过，听到的是飞机引擎被消声后的声音。
Devices with built-in microphones located close to the ear
在降噪设备靠近耳朵的位置内置麦克风
means headphones only have microseconds to calculate an antiphase signal and send the ambient sound to your ears.
意味着耳机只有几微秒的时间来计算反相信号，还要把消声后的环境噪音传入你的耳朵。
It works well for low-frequency sounds, but noise-canceling headphones struggle with shorter, high-frequency sound waves.
这种降噪耳机消除低频噪音时效果很好，但对波长更短，频率更高的高频噪声就显得吃力了。
So if you’re looking to shut out noise like human voices, dogs barking and babies crying,
所以，如果你想屏蔽的是人发出的噪音，狗叫声或是婴儿的哭闹声，
you’re going to need that passive noise cancellation too.
那你就还需要上面提到的被动降噪技术。
However, some active noise-canceling headphones can have a noticeable distinct hiss.
不过，一些主动降噪耳机会发出明显能听得到的嘶嘶声。
This hiss is called the “noise floor,” and it’s actually made by the electronic circuitry itself.
这个嘶嘶声就是所谓的“噪底”，它其实是耳机内部的电子线路本身发出的一种噪声。
A lack of uniformity in the copper wire, sensors, and soldering cause electrons to stutter or bounce,
原来，铜线、传感器和焊剂的不均匀都会导致电子卡顿或反弹继而产生噪声，
producing noise that’s present in all electronic devices from cell phones to amplifiers.
所有电子设备，无论是手机还是放大器都有这种噪声。
Depending on the quality of the headphones,
鉴于耳机质量不一，
newer models are able to minimize this unwanted sound, which is often reflected in their price.
有些新款耳机是能够最大限度地降低这种多余的噪音的，这一性能往往也体现在了耳机的价格上。
In the future, you might not have to put on bulky headphones or shove a device in your ear to experience the benefits of active noise cancellation.
或许，有朝一日，不用戴笨重的头戴式耳机也不用塞耳塞式耳机，你就能感受到主动降噪技术的福音。
It's appeared in cars that use accelerometers in combination with microphones
目前，一些同时配备了加速记和麦克风的汽车就已经在运用这项技术，
to measure the vibration of sounds coming from uneven pavement, reducing the noise that passengers hear.
测量不平路面发出的声音振动，降低乘客听到的噪音了。
For more stationary environments, engineers at the University of Illinois are researching how to take advantage of the fact
至于在这种技术在静态环境下的应用，伊利诺伊大学的工程师们也已经着手
that wireless signals travel a million times faster than sound.
无线信号的传播速度比声音快一百万倍这一事实有关的研究了。
By placing microphones closer to a noise source, like chatty coworkers,
通过把麦克风放在离噪声源，比如喋喋不休的同事更近的地方，
a more accurate cancellation signal can be transmitted to an ear device faster than the speed of sound—all before the sound even arrives at the listener.
更准确的消声信号就能在声音到达听者耳朵之前，以比声速更快的速度传输到耳机设备里。
Noise cancellation technology has come a long way since the Voyager flight,
自“旅行者”号的那次飞行以来，降噪技术已经取得了长足的进步，
and it looks like we can expect to see some exciting developments in the near future.
目前看来，一些令人振奋的突破已经指日可待。
But if you’re planning on wearing your noise-canceling headphones,
但是，如果你还是想戴着你的降噪耳机的话，
you might want to take them off every once in a while, or you won’t hear the news.
那建议你每隔一段时间就把它取下来一会儿，以免错过好消息噢。
Fun fact: Speaking of sound, the term misophonia literally means “hatred of sound”.
小资料：说到声音，“恐音症”一词的字面意思其实是“憎恶（某种）声音”。
It’s a condition where negative emotions, thoughts, or physical response is triggered by specific sounds.
指的是特定的声音会引发负面情绪，负面念头或负面的生理反应。
So tell us, what sounds do you find absolutely intolerable?
那么问题来咯，哪些声音是你觉得完全忍受不了的呢？
Let us know down in the comments and don’t forget to subscribe to Seeker.
快在评论下方告诉我们吧。还有，别忘了订阅我们的频道噢。
Thanks for watching!
感谢大家的收看！
