subway, or a crowded street,

地鐵，或擁擠的街道。

noise-canceling headphones will drown out

降噪耳機會淹沒在噪音中

almost everything around you.

幾乎你周圍的一切。

Bringing peace and quiet to your ears.

帶來耳邊的寧靜和安寧。

But how do they actually work?

但它們的實際效果如何呢？

You've probably seen noise-canceling headphones

你可能已經看到了降噪耳機

become pretty widespread over the last decade or so.

在過去的十幾年裡變得相當普遍。

But did you know the concept

但你知道這個概念嗎？

actually dates back to 1978?

其實可以追溯到1978年？

That's when Dr. Amar Bose took a flight

這時，阿瑪爾-博斯博士坐上了飛機

from Zurich to Boston.

從蘇黎世到波士頓。

He became frustrated that the noise of the plane

他感到沮喪，飛機的噪音。

drowned out the music playing

喧賓奪主

through the electronic headsets on the flight.

通過飛行中的電子耳麥。

Now, Bose's name might sound familiar.

現在，Bose的名字可能聽起來很熟悉。

He is the founder of Bose audio,

他是Bose音響的創始人。

which has become synonymous with noise-canceling headphones.

已成為降噪耳機的代名詞。

However, it would take several years

然而，這需要幾年時間

and millions of dollars in research for that to happen.

以及數百萬美元的研究經費。

Which all began on this flight.

這一切都始於這次飛行。

When Bose designed his first concept

當Bose設計他的第一個概念時

for noise-canceling technology.

為降噪技術。

Bose's solution was simple.

Bose的解決方案很簡單。

He would design headphones that listen.

他要設計出能聽的耳機。

But it was easier said than done.

但說起來容易做起來難。

By 1986, almost 10 years after his fateful flight,

到1986年，在他的致命飛行近10年後。

Bose had a working prototype,

Bose有一個工作原型。

which soon became a product for airline pilots,

很快就成為航空公司飛行員的產品。

the military, and eventually

軍隊，最終

first- and business-class customers

頭等艙和商務艙客戶

aboard American Airlines.

在美國航空公司的飛機上。

Eventually, once costs came down,

最終，一旦成本下降。

the headphones began to become available

耳機開始上市

to the general public.

向公眾開放。

And while you listen to things through the speakers,

而當你通過揚聲器聽東西的時候。

the headphones are listening as well

耳機也在聽

to everything around you.

對你周圍的一切。

See, every sound travels in the form of a wave,

你看，每個聲音都是以波的形式傳播的。

also called a sound wave.

也叫音波。

And each one is different.

而且每個人都不一樣。

This is a sound wave of me saying "hello."

這是我說 "你好 "的聲波。

And here is "goodbye."

而這裡是 "再見"。

See? They're different.

看到了嗎？他們是不同的。

Now, if you played both sounds at the same time,

現在，如果你同時演奏這兩種聲音。

you'd get a phenomenon called constructive interference.

你會得到一種叫做建設性干擾的現象。

Constructive interference amplifies sound

構造性干擾會放大聲音

to make the overall combination louder.

以使整體組合更響亮。

It's the same phenomenon you get in a crowded restaurant.

這和你在人多的餐廳裡的現象是一樣的。

As more people come in and start talking,

隨著越來越多的人進來，開始說話。

the overall sound you hear is louder.

你聽到的整體聲音更響亮。

But what if instead of becoming a louder sound,

但如果不是變成更響亮的聲音呢。

it became quieter?

它變得更安靜？

In fact, it became so quiet, it was almost silent?

事實上，它變得非常安靜，幾乎無聲無息?

That's called destructive interference.

這就是所謂的破壞性干擾。

And it's exactly what our

而這正是我們的

noise-canceling headphones are doing.

降噪耳機在做。

Let's go back to those sound waves from before.

讓我們回到之前的那些聲波。

See, sound waves, like light waves, have peaks and valleys.

你看，聲波和光波一樣，也有波峰和波谷。

Noise-canceling headphones have

降噪耳機有

their own built-in microphone.

自己的內置麥克風。

And when the headphone's microphone detects a sound wave,

而當耳機的麥克風檢測到聲波時。

the headphones create a new waveform

耳機產生一個新的波形

that's the total opposite.

這是完全相反的。

So for every valley there is a peak,

所以每一個山谷都有一個高峰。

and for every peak, a valley.

每一座山峰，都有一個山谷。

What results is the canceling part of noise-canceling.

結果就是消除噪音的部分。

The waves cancel each other out, and a flat line ensues.

浪潮相互抵消，隨之而來的是一條平線。

Blissful silence.

幸福的沉默。

Now, if you've used noise-canceling headphones before,

現在，如果你以前用過降噪耳機。

you've probably noticed they

你可能已經注意到他們

don't cancel out every single noise.

不要取消每一個噪音。

Some other noises leak through sometimes,

其他一些噪音有時也會漏掉。

like people talking loudly

侃大山

or cars honking.

或汽車鳴笛。

That's because the technology works best

這是因為該技術效果最好

in environments with consistent noise.

在噪音一致的環境中。

Which is why the headphones are ideal

這就是為什麼耳機是理想的

in places like airplane cabins

在飛機艙等地方

or train cars.

或火車車廂。

In other cases, with too much variation,

在其他情況下，隨著變化太大。

matching the sound wave is tricky.

匹配聲波是很棘手的。

It's kind of like whack-a-mole.

這有點像捶地鼠。

You can only eliminate so many sounds at once.

你只能一次消除這麼多聲音。

And some headphones will be better than others.

而有些耳機會比其他耳機更好。

While a $50 pair may not eliminate noises

雖然50美元的一對可能無法消除噪音

the way a $300 set does,

300元一套的方式。

it may be good enough for your needs.

它可能是足夠好的，以滿足您的需求。

Even if they don't achieve perfect silence every time,

即使他們並不是每次都能達到完美的沉默。

there's no doubt noise-cancellation technology

毋庸置疑的是，降噪技術。

has been a useful way to help people get through

一直是幫助人們渡過難關的有效途徑。

their days or commutes.

他們的日子或通勤。

It looks like the $50 million Bose spent back then

看來，Bose當年花的5000萬美金。

turned out to be great in the long run.

從長遠來看，原來是很好的。