Luca Turin: The science of scent

譯者: Ching-Yi Wu 審譯者: Wang-Ju Tsai

The fragrance that you will smell, you will never be able to smell this way again.

你待會兒聞到的香氣，絕不會有機會以這種方式聞第二次

It’s a fragrance called Beyond Paradise,

這香水名為「霓采天堂」

which you can find in any store in the nation.

在國內的店裡找不到

Except here it’s been split up in parts by Estée Lauder

除非你去跟雅詩蘭黛要一點來

and by the perfumer who did it, Calice Becker,

或是跟香水師Calice Becker要

and I'm most grateful to them for this.

我很感激他們分我一些

And it’s been split up in successive bits and a chord.

香氣可拆開成接連散發並組合如和弦的各種氣味

So what you’re smelling now is the top note.

而妳現在所聞到的就是首調

And then will come what they call the heart, the lush heart note.

緊接著的引人入勝氣味被稱為中調

I will show it to you.

等會我將讓各位聞聞

The Eden top note is named after the Eden Project in the U.K.

「霓采天堂」的首調「伊甸」是以英國的伊甸園計畫命名的

The lush heart note, Melaleuca bark note -- which does not contain any Melaleuca bark,

中調則是白千層樹皮──然而香水裡其實沒有這個成份

because it’s totally forbidden.

因為它被禁用

And after that, the complete fragrance.

最後，則是完整的香氣

Now what you are smelling is a combination of --

現在你所聞到的組合是──

I asked how many molecules there were in there, and nobody would tell me.

我曾問，香水中有什麼分子。沒有人想告訴我

So I put it through a G.C., a Gas Chromatograph that I have in my office,

所以我把香水以我辦公室裡的氣相層析儀分析

and it’s about 400.

發現裡頭大概有400種分子

So what you’re smelling is several hundred molecules

也就是說，你正在聞數百個

floating through the air, hitting your nose.

漂浮在空氣中、撞擊鼻腔的分子

And do not get the impression that this is very subjective.

如果這個事實還不夠令人印象深刻的話

You are all smelling pretty much the same thing, OK?

你們所聞到的香氣成份其實相當接近啊

Smell has this reputation of being somewhat different for each person.

嗅覺向以每個人都有不同的感受聞名

It’s not really true.

這並不完全正確

And perfumery shows you that can’t be true,

只需要一瓶香水就能證明這一點

because if it were like that it wouldn’t be an art, OK?

因為如果真是這樣，香水就不會是個藝術，你明白嗎？

Now, while the smell wafts over you, let me tell you the history of an idea.

當陣陣香氣襲向各位時，我想談談一個點子的歷史

Everything that you’re smelling in here

你在這裡所聞到的每種香氣

is made up of atoms that come from what I call

都是由一群位在，被我稱為

the Upper East Side of the periodic table -- a nice, safe neighborhood.

週期表上東城──一個安全美好的區域──的分子組成

(Laughter)

（笑）

You really don’t want to leave it if you want to have a career in perfumery.

如果你想在香水業立足，你絕對不會想離開這區

Some people have tried in the 1920s

有些人在1920年代曾經試著

to add things from the bad parts, and it didn’t really work.

在香水裡加入週期表其他區塊的分子，但是沒有成功

These are the five atoms from which just about everything

上東城裡的五個分子幾乎就能組成

that you’re going to smell in real life, from coffee to fragrance, are made of.

你生活裡從咖啡跟香水等所有的氣味，

The top note that you smelled at the very beginning,

而你剛剛一開始所聞到的前調

the cut-grass green, what we call in perfumery -- they’re weird terms --

在我們香水業被稱做清新草原味──很怪的叫法

and this would be called a green note,

而之所以這麼稱呼綠葉調

because it smells of something green, like cut grass.

是因為它聞來就像綠色植物，如草原的氣息

This is cis-3-hexene-1-ol. And I had to learn chemistry on the fly

這是順式-3-己烯醇。我過去三年

in the last three years. A very expensive high school chemistry education.

得抽空學習化學。非常昂貴的高中化學教育

This has six carbon atoms, so "hexa," hexene-1-ol.

順式-3-己烯醇有六個碳分子，所以"hexanol"以hexa-為字首

It has one double bond, it has an alcohol on the end,

分子裡有一個雙鍵，分子末端有乙醇

so it’s "ol," and that’s why they call it cis-3-hexene-1-ol.

所以"hexanol"以-ol為字尾。這是順式-3-己烯醇的命名由來。

Once you figure this out, you can really impress people at parties.

一旦你懂得分子命名原則，你就能在派對上唬人

This smells of cut grass. Now, this is the skeleton of the molecule.

順式-3-己烯醇聞來就像草原。這是分子的碳鏈

If you dress it up with atoms, hydrogen atoms --

你可以用電腦在碳鏈上加氫原子

that’s what it looks like when you have it on your computer --

這時順式-3-己烯醇看起來像這樣

but actually it’s sort of more like this, in the sense that the atoms have a certain

但因為每個元素都有個不能侵入的圓形區域─

sphere that you cannot penetrate. They repel.

它們互斥─所以順式-3-己烯醇實際上長這樣

OK, now. Why does this thing smell of cut grass, OK?

好，現在問題來了：為什麼這分子聞起來是草原味，

Why doesn’t it smell of potatoes or violets? Well, there are really two theories.

而不是馬鈴薯，或是紫羅蘭？有兩個理論：

But the first theory is: it must be the shape.

第一個理論是關於分子的形狀。

And that’s a perfectly reasonable theory in the sense that

這是個完美的理論，因為在生物界

almost everything else in biology works by shape.

幾乎所有的功能都由分子形狀決定

Enzymes that chew things up, antibodies, it’s all, you know,

如分解分子的酵素、抗體，一切取決於蛋白質

the fit between a protein and whatever it is grabbing, in this case a smell.

跟其他分子間的緊密結合。而嗅覺也是

And I will try and explain to you what’s wrong with this notion.

我等一下會試著解釋這個理論哪裡不對

And the other theory is that we smell molecular vibrations.

另一個理論則是說嗅覺是我們聞到分子的震動

Now, this is a totally insane idea.

這個想法完全沒有道理

And when I first came across it in the early '90s, I thought my predecessor,

而我在90年代早期第一次聽到這個想法時

Malcolm Dyson and Bob Wright, had really taken leave of their senses,

覺得Dyson跟Wright這些先驅者的直覺失準

and I’ll explain to you why this was the case.

我等一下會告訴你們為什麼

However, I came to realize gradually that they may be right --

然而，我漸漸明白，他們也許是對的

and I have to convince all my colleagues that this is so, but I’m working on it.

我得說服我的同行接受這個理論，而我仍在努力

Here’s how shape works in normal receptors.

這是分子跟其受器間作用機制的形狀說圖解

You have a molecule coming in, it gets into the protein, which is schematic here,

一個分子進入一個蛋白質，當兩者的形狀吻合

and it causes this thing to switch, to turn, to move in some way

分子會跟蛋白質的一部分結合

by binding in certain parts.

造成這個複合體的變型、扭轉或移動

And the attraction, the forces, between the molecule and the protein

而分子跟蛋白質之間的吸引力造成這樣的運動模式

cause the motion. This is a shape-based idea.

就是這個以分子形狀為基礎的理論

Now, what’s wrong with shape is summarized in this slide.

而這個分子形狀理論的問題摘要在這投影片上

The way --I expect everybody to memorize these compounds.

希望大家還記得這些物質

This is one page of work from a chemist’s workbook, OK?

這是一位在香水公司工作的化學家

Working for a fragrance company.

其實驗筆記的一頁

He’s making 45 molecules, and he’s looking for a sandalwood,

因為檀香味的龐大商機

something that smells of sandalwood.

他得找出檀香味，或是類似檀香的味道

Because there’s a lot of money in sandalwoods.

所以他製造了45個分子

And of these 45 molecules, only 4629 actually smells of sandalwood.

而這45個分子中，只有4629分子聞起來是檀香

And he puts an exclamation mark, OK? This is an awful lot of work.

他加註驚嘆號，對吧？這是非常繁重的工作

This actually is roughly, in man-years of work, 200,000 dollars roughly,

以一個人一年工時計，如果你給他無利潤的低薪

if you keep them on the low salaries with no benefits.

其收入約為20萬美金

So this is a profoundly inefficient process.

所以這是個非常沒有效率的工作

And my definition of a theory is, it’s not just something

而我對理論的定義，不僅只是

that you teach people; it’s labor saving.

被傳授的知識，更得幫助節省勞力

A theory is something that enables you to do less work.

一個理論得讓人們事半功倍

I love the idea of doing less work. So let me explain to you why -- a very simple fact

我喜歡省力的主意。請讓我解釋

that tells you why this shape theory really does not work very well.

形狀理論之所以無用的單純現實

This is cis-3-hexene-1-ol. It smells of cut grass.

這是順式-3-己烯醇，聞起來像草原

This is cis-3-hexene-1-thiol, and this smells of rotten eggs, OK?

這是順式-3-己硫醇，聞起來像腐敗的蛋

Now, you will have noticed that vodka never smells of rotten eggs.

你也知道伏特加聞起來絕對不像腐敗的蛋

If it does, you put the glass down, you go to a different bar.

如果是，你會放下酒杯，改去另一間酒吧

This is -- in other words, we never get the O-H --

換句話說，我們不會對弄錯醇類

we never mistake it for an S-H, OK?

不會搞混醇類跟硫化物

Like, at no concentration, even pure, you know,

這跟濃度無關，即使讓你聞純酒精

if you smelt pure ethanol, it doesn’t smell of rotten eggs.

也不會聞到壞蛋的臭味

Conversely, there is no concentration at which the sulfur compound will smell like vodka.

反之，再純的硫化物也不會聞起來像伏特加

It’s very hard to explain this by molecular recognition.

我們很難用蛋白質辨識分子形狀的不同來解釋這個現象

Now, I showed this to a physicist friend of mine who has a profound distaste

而我如此向我那對生物學完全沒興趣的

for biology, and he says, "That’s easy! The things are a different color!"

物理學家朋友說明，他說：「這容易，兩種不同顏色的東西！」

(Laughter)

（笑）

We have to go a little beyond that. Now let me explain why vibrational theory has

更進一步，現在讓我來解釋為什麼振動理論

some sort of interest in it. These molecules, as you saw in the beginning,

有趣。這些分子，如你一開始所見

the building blocks had springs connecting them to each other.

組成分子的原子間有如彈簧般的連結

In fact, molecules are able to vibrate at a set of frequencies

不同的分子的震動包含不同頻率

which are very specific for each molecule and for the bonds connecting them.

頻率組成視分子，或是組成分子的原子間的連結而定

So this is the sound of the O-H stretch, translated into the audible range.

這是將O-H鍵的振動頻率轉換成人類聽力範圍的聲音

S-H, quite a different frequency.

而S-H鍵振動頻率則相當不同

Now, this is kind of interesting, because it tells you

這個現象最有趣的部分

that you should be looking for a particular fact, which is this:

在提醒我認清這個特定事實，也就是

nothing in the world smells like rotten eggs except S-H, OK?

這個世界上除了腐爛的蛋，沒有別的東西聞起來像硫氫化物了

Now, Fact B: nothing in the world has that frequency except S-H.

再者：這個世界上除了有硫氫化物，沒有別的分子能以這樣的頻率振動

If you look on this, imagine a piano keyboard.

你也可以這麼看：想像一個鋼琴鍵盤

The S-H stretch is in the middle of a part of the keyboard

代表S-H鍵的振動頻率的琴鍵位在鍵盤某處的中間

that has been, so to speak, damaged,

這個琴鍵壞掉了

and there are no neighboring notes, nothing is close to it.

周圍及其他的琴鍵沒有一個能發出接近它的音頻

You have a unique smell, a unique vibration.

而氣味也有這樣的獨特性，獨特的震動

So I went searching when I started in this game

為了自我說服

to convince myself that there was any degree of plausibility

這整個瘋狂的理論是可信的

to this whole crazy story.

我開始這個尋找氣味分子的遊戲

I went searching for a type of molecule, any molecule,

我想找到某個類型的分子，或任何分子

that would have that vibration and that -- the obvious prediction

其振動頻率跟硫氫化物一樣

was that it should absolutely smell of sulfur.

若理論正確，顯然這分子聞起來像硫磺

If it didn’t, the whole idea was toast, and I might as well move on to other things.

如果不是這樣，這整個理論是個餿主意，我會轉而研究其他主題

Now, after searching high and low for several months,

在經過幾個月有高潮有低潮的研究

I discovered that there was a type of molecule called a Borane

我發現有種叫做硼烷的分子

which has exactly the same vibration.

跟硫氫化物有一模一樣的振動頻率

Now the good news is, Boranes you can get hold of.

好消息是，我們能拿到一些硼烷

The bad news is they’re rocket fuels.

而壞消息是，硼烷是火藥的燃料

Most of them explode spontaneously in contact with air,

一但跟空氣接觸，大部分的硼烷會自動爆炸

and when you call up the companies, they only give you minimum ten tons, OK?

若你打電話給硼烷公司訂購，他們至少得賣你十噸好嗎？

(Laughter)

（笑）

So this was not what they call a laboratory-scale experiment,

這並不是所謂的實驗室規模的實驗

and they wouldn’t have liked it at my college.

而我的學校高層並不欣賞這樣的研究

However, I managed to get a hold of a Borane eventually, and here is the beast.

然而，我到底還是拿到一些硼烷了，就是這個怪獸

And it really does have the same -- if you calculate,

經過計算跟測量

if you measure the vibrational frequencies, they are the same as S-H.

硼烷的振動頻率的確硫氫化物相同

Now, does it smell of sulfur? Well, if you go back in the literature,

現在問題來了，硼烷的味道跟硫氫化物一樣嗎？

there’s a man who knew more about Boranes than anyone

Alfred Stock，有史以來最懂硼烷的人

alive then or since, Alfred Stock, he synthesized all of them.

當他還在世時，他合成了所有硼烷化合物

And in an enormous 40-page paper in German he says, at one point --

在一篇長達40頁，以德文寫就的大論文裡，他提到一點──

my wife is German and she translated it for me --

我的妻子是德國人，是她幫我翻譯原文的

and at one point he says, "ganz widerlich Geruch,"

Alfred Stock這麼說："ganz widerlich Geruch"

an "absolutely repulsive smell," which is good. Reminiscent of hydrogen sulfide.

意即：「非常難聞的味道」。很好，這讓我想起了硫化氫。

So this fact that Boranes smell of sulfur

這就是說，早在1910年，就已知硼烷的味道

had been known since 1910, and utterly forgotten until 1997, 1998.

跟硫化氫相同，之後直至1997, 98年都一直被人遺忘

Now, the slight fly in the ointment is this: that

而有點美中不足的是：

if we smell molecular vibrations, we must have a spectroscope in our nose.

如果我們的嗅覺是在辨別分子振動，我們的鼻子中必定有個光譜儀

Now, this is a spectroscope, OK, on my laboratory bench.

這就是光譜儀，好吧，其實是我實驗桌上的光譜儀

And it’s fair to say that if you look up somebody’s nose,

公道的說，當你看著一個人的鼻子時

you’re unlikely to see anything resembling this.

你不太可能覺得鼻子跟這個東西有任何相似之處

And this is the main objection to the theory.

這是這理論最主要的反證

OK, great, we smell vibrations. How? All right?

好吧，我們聞得出分子的振動。然而，這是怎麼辦到的？

Now when people ask this kind of question, they neglect something,

當人們問這個問題時，他們忽略了一件事

which is that physicists are really clever, unlike biologists.

那就是：物理學家的確很聰明，不像生物學家

(Laughter)

（笑）

This is a joke. I’m a biologist, OK?

這是個笑話，我到底還是個生物學家

So it’s a joke against myself.

這笑話是對我的反諷

Bob Jacklovich and John Lamb at Ford Motor Company,

當福特汽車還投資大量金錢

in the days when Ford Motor was spending vast amounts of money

在基礎研究上時，公司職員

on fundamental research, discovered a way

Bob Jacklovich跟John Lamb找到了

to build a spectroscope that was intrinsically nano-scale.

製作內建奈米級光譜儀的方法

In other words, no mirrors, no lasers, no prisms, no nonsense,

換句話說，這個小儀器不需要鏡子、

just a tiny device, and he built this device. And this device uses electron tunneling.

雷射、稜鏡等沒有必要的東西，而是利用電子隧穿的原理

Now, I could do the dance of electron tunneling,

我是可以跳個電子隧穿舞

but I’ve done a video instead, which is much more interesting. Here’s how it works.

不過，我還是製作一段更有趣的影片，來告訴你們這是怎麼辦到的

Electrons are fuzzy creatures, and they can jump across gaps,

電子是非常活躍的物質，他們能夠跳越

but only at equal energy. If the energy differs, they can’t jump.

兩個能量相同的能隙。當能隙能量不同時，則無法跨越

Unlike us, they won’t fall off the cliff.

跟我們不同，電子不會從由能量差構成的懸崖摔下

OK. Now. If something absorbs the energy, the electron can travel.

如果有某個物質吸收能量，電子就能夠游移

So here you have a system, you have something --

而這個系統──

and there’s plenty of that stuff in biology --

生物體中有很多這樣的系統──

some substance giving an electron, and the electron tries to jump,

某些物質提供電子，這些電子試著穿越能隙

and only when a molecule comes along that has the right vibration

只有具正確振動頻率的某分子存在時

does the reaction happen, OK?

反應才會發生

This is the basis for the device that these two guys at Ford built.

這是福特的兩位職員發明的奈米光譜儀的原理

And every single part of this mechanism is actually plausible in biology.

這個機器的每一個部份在生物學上都行得通

In other words, I’ve taken off-the-shelf components,

也就是說，我曾經拆開過這個儀器

and I’ve made a spectroscope.

自己做過光譜儀

What’s nice about this idea, if you have a philosophical bent of mind,

如果你天生就是個好學之士，你會明白

is that then it tells you that the nose,

這個點子最棒之處，在於揭示所有的感官

the ear and the eye are all vibrational senses.

包括嗅覺聽覺跟視覺都是在感覺分子的振動

Of course, it doesn’t matter, because it could also be that they’re not.

當然，這不重要，因為也有可能不是這樣

But it has a certain --

但是，這理論在某種程度上──

(Laughter)

（笑）

-- it has a certain ring to it which is attractive to people

在某種程度上對讀了很多19世紀時的

who read too much 19th-century German literature.

德國文獻的人們是有吸引力的

And then a magnificent thing happened:

當年，巨大的轉折出現：

I left academia and joined the real world of business,

我離開學術圈，進入產業界的現實世界

and a company was created around my ideas

根據我的想法成立一個公司

to make new molecules using my method,

並利用我的技術合成新分子

along the lines of, let’s put someone else’s money where your mouth is.

也就是讓別人來投資我的信念

And one of the first things that happened was

一開始

we started going around to fragrance companies

我們去拜訪香水公司

asking for what they needed, because, of course,

問他們需要什麼。當然，這是因為

if you could calculate smell, you don’t need chemists.

如果你能量化味道，就不需要化學家

You need a computer, a Mac will do it, if you know how to program the thing right,

只要一部蘋果電腦，跟寫出正確的程式

OK? So you can try a thousand molecules,

就能計算一千個分子

you can try ten thousand molecules in a weekend,

一個周末你就能處理一萬個分子

and then you only tell the chemists to make the right one.

再讓化學家去合成味道正確的分子

And so that’s a direct path to making new odorants.

這是合成新味道的直接途徑

And one of the first things that happened was

剛開始

we went to see some perfumers in France --

我們去拜訪法國的香水師─

and here’s where I do my Charles Fleischer impression --

這時我模仿Charles Fleischer的演出─

and one of them says, "You cannot make a coumarin."

他們之中有一個人說：「你才做不來香豆素的味道。」

He says to me, "I bet you cannot make a coumarin."

「我賭你做不來。」

Now, coumarin is a very common thing, a material,

香豆素是非常常見的香水原料

in fragrance which is derived from a bean that comes from South America.

這個味道是從南美洲的一種豆子提煉出來的

And it is the classic synthetic aroma chemical, OK?

但也是個典型的人工合成香味

It’s the molecule that has made men’s fragrances

這個分子讓男性香水的味道

smell the way they do since 1881, to be exact.

從1881年以來就沒有變過

And the problem is it’s a carcinogen.

但問題是，香豆素致癌

So nobody likes particularly to -- you know, aftershave with carcinogens.

而沒有人會希望他不過是刮個鬍子就會接觸致癌物

(Laughter)

（笑）

There are some reckless people, but it’s not worth it, OK?

總是有不在乎的人，但還是不值得嘛！

So they asked us to make a new coumarin. And so we started doing calculations.

所以他們希望我們合成新的香豆素。我們也做了計算

And the first thing you do is you calculate the vibrational spectrum

首先，得計算香豆素的振動頻率譜

of coumarin, and you smooth it out,

並整理結果來讓我們

so that you have a nice picture of what the sort of chord, so to speak, of coumarin is.

對香豆素是個怎樣的香調有比較好的認識

And then you start cranking the computer to find other molecules,

接著，是利用電腦分析類似香豆素的分子

related or unrelated, that have the same vibrations.

不相干的分子也可以，來找跟香豆素振動方式相同的分子

And we actually, in this case, I’m sorry to say,

而我們的確，就這個案例，我不得不這麼說

it happened -- it was serendipitous.

這方法行得通──我們運氣不錯

Because I got a phone call from our chief chemist

當時我們的首席化學家打電話給我

and he said, look, I’ve just found this such a beautiful reaction,

說他剛剛發現一個很美妙的化學反應

that even if this compound doesn’t smell of coumarin,

所以就算反應產物聞起來不像香豆素

I want to do it, it’s just such a nifty,

他還是想研究這個有效率的、只要一個步驟的反應──

one step -- I mean, chemists have weird minds --

化學家都有個怪腦袋

one step, 90 percent yield, you know, and you get this lovely

反正只要一步，我們就能得到這個可愛的結晶物

crystalline compound. Let us try it.

產率達90%。讓我們試試看吧

And I said, first of all, let me do the calculation on that compound, bottom right,

我說：首先，我們來對這個物質進行些計算

which is related to coumarin, but has an extra pentagon inserted into the molecule.

它的部分結構近似香豆素，但多了一個五碳環

Calculate the vibrations, the purple spectrum is that new fellow,

這是結果，紫色表示這個新物質的振動頻率譜

the white one is the old one.

而白色的就是香豆素

And the prediction is it should smell of coumarin.

預測顯示，新物質聞起來應該像香豆素

They made it ... and it smelled exactly like coumarin.

新物質作出來以後，味道正是香豆素的味道

And this is our new baby, called tonkene.

這是我們的新寶物，香豆烯

You see, when you’re a scientist, you’re always selling ideas.

你看，當你是個科學家時，你總是在賣你的想法

And people are very resistant to ideas, and rightly so.

然而人們抗拒新點子，問題也正是：

Why should new ideas be accepted?

為什麼我們得接受新點子？

But when you put a little 10-gram vial on the table in front of perfumers

但當你在香水師的桌前放上少少的10克

and it smells like coumarin, and it isn’t coumarin,

"聞起來像香豆素，卻不是香豆素"的物質

and you’ve found it in three weeks,

而你只花三個星期找到它

this focuses everybody’s mind wonderfully.

這讓每個人都覺得棒極了

(Laughter)

（笑）

(Applause)

（掌聲）

And people often ask me, is your theory accepted?

人們常問：你的理論被接受了嗎？

And I said, well, by whom? I mean most, you know -- there’s three attitudes:

我說：被誰接受呢？聽到這理論的人大致有三種反應：

You’re right, and I don’t know why, which is the most rational one at this point.

雖然我不明白，但你是對的，這是目前最合理的推測

You’re right, and I don’t care how you do it, in a sense;

你大概是對的，而我也不在乎你是怎麼辦到的

you bring me the molecules, you know.

反正你都把新分子給我了

And: You’re completely wrong, and I’m sure you’re completely wrong.

還有：你錯了，我很確定你一定是錯的

OK? Now, we’re dealing with people who only want results,

也就是說，我們得面對只在乎結果的人

and this is the commercial world.

而這是個資本主義世界

And they tell us that even if we do it by astrology, they’re happy.

他們說，就算我們是靠著占星學知識達成任務，他們還是滿意的

But we’re not actually doing it by astrology.

但我們的確不是靠著占星學知識達成任務

But for the last three years, I’ve had what I consider to be

在最近三年，我做著一份我認為是

the best job in the entire universe, which is to put my hobby --

全宇宙最棒的工作：這讓我能將我的嗜好

which is, you know, fragrance and all the magnificent things --

也就是香氛跟所有美好的事物

plus a little bit of biophysics, a small amount of self-taught chemistry

跟一些些生理學，一些些自學來的化學結合起來

at the service of something that actually works.

做出一些實際有用的貢獻

Thank you very much.

非常謝謝大家

(Applause)

（掌聲）