[談談現實中的豎笛--簡化版]

什麼是豎笛?(又來了!)

我且用一個更實際點的說法來回答這個問題: 如果你先用豎笛吹個中央C
(請注意,對Bb調豎笛而言它的"中央C"事實上是鋼琴上的Bb),然後再試著吹出這個
音的下一個泛音,你會發現你現在吹出來的是和上個音相距完全十二度的G,而繼續
相同的方式下去,你會吹出所謂的"兩點"Mi(和上一個泛音G相距大六度),依此類推
.... 相反的,如果你以長笛或雙簧管或是薩克斯風來作上述的練習,你會發現你吹
出的泛音是C,高音C(高八度),高音G(高完全五度),......

這就是我前一篇中討論理想豎笛的部分所得到的結論.

我必須先介紹很多也許你們之中的大多數已經知道的東西.但是對我來說
,如果要繼續討論接下來的東西,除了先將這些東西解釋清楚外,似乎也沒有更好的
選擇.

組成任何樂器音色的要素其實都非常複雜,否則這些樂器發出的聲音將與
我們說話的聲音非常相近.對於分析豎笛的音色而言, 我們最好先研究組成它聲音
的頻譜.

那麼,什麼是"頻譜"呢?

我們可以把豎笛所發出的聲音看成是許多單獨頻率的聲波的組合.而我們
可以從頻譜圖上看出每個頻率的聲波在合成整個聲波時所佔的份量.假如440 Hz這
個頻率在整個聲波中所佔的份量很大,那麼在頻譜圖中就會有個尖線出現.

(如圖:
|
|
大 | |
小 | |
|____________|____________
440 Hz 頻率 )

接著就讓我們用可以測出聲音頻譜的機器(Tony曰: 就是所謂的"頻譜分
析儀",這種儀器頗高檔,買一台可要不少麥克麥克,不過一般的學校實驗室中可以
找到,好比p..l先生的老師就有一台)來分析豎笛的聲音.

現在,如果你用豎笛吹一個中央C--就是你用豎笛所能吹出最低的那個C,
那麼頻譜就會在你所吹的那個C所對應的頻率上出現一條較大的尖線.然後你還會
在圖上看到在這個頻率的三,五,七倍頻率的地方也有一些較小的尖線出現. 這正
是我們預期閉管樂器會發生的現象. 但是你還是可以在二,四,六倍頻率附近的地
方看到很小的尖線出現. 這說明了真正的豎笛的特性和我上次介紹的"理想豎笛"
還是有所不同的.真正的豎笛畢竟不是完美的"閉管"樂器.對豎笛來說,其整個"蕭
呂摩"音域(Tony曰: CHALUMEAU這是種古老的樂器,跟迅猛龍一樣,現在絕跡啦.它
可以算是豎笛的前身,就像人類與猴子的關係一般.一般將其譯作"蕭魔"--取其音
譯或是"蕭笛",我則是以英文的念法來音譯.豎笛最低的音域--E~Bb的音色與這種
樂器相近,所以這個音域就稱為豎笛的"蕭呂摩音域")的音都有類似的頻譜圖形.
正是因為缺乏了基頻的第二,四,六...倍頻率的成分,才造就了豎笛這個音域中的
獨特的音色,而這也是豎笛的特徵.

接著,再吹一個剛才中央C的完全十二度的音.當然,這個音是G.除了必須
按下左手拇指的泛音鍵以幫助這個音容易發出以外,這個音的指法和中央C的指法
是完全相同的.而這個音已經在豎笛的"克拉蓉"音域之中了(Tony曰:Clarion是一
種古代的木製高音小號. 豎笛中高音域的音色和這種樂器相近,故B~C''的這音域
稱為clarion.甚至連豎笛clarinet這個字都是源自於CLARION.在這裡一樣是音譯
)這個音域的頻譜和蕭呂摩音域的頻譜在性質上已經有相當大的改變了.當然對應
於最低的頻率的那條尖線還是G音的頻率,但是其偶數倍頻率的成分已經不是那麼
小了.這些偶數頻的泛音還是比基數頻的泛音的成分來的小,但相差不多了. 這對
整個克拉蓉音域的音來說都是如此.即,從B(對Bb調豎笛來說,這個音的頻率是440
Hz)到高音C都是.

"等等!"也許你會問,"即使你說它們的頻譜在性質上已經改變了,我還是
可以分辨的出那是豎笛的聲音呀."

很好,你只是在告訴我人的耳朵有多好罷了.我們可以分辨出有人正在吹
豎笛而不是長笛或是薩克斯風其聲音頻譜上微小的差異.

那麼再下一個音域的頻譜又是如何呢?

基本上你只能從其頻譜上看到兩個尖線,最多三個. 也就是說,如果你吹
一個高音E("兩點Mi"), 那麼你可以在更高八度的E("三點Mi")的頻率附近再看到
一條尖線,然後還可以在更高的高音B("三點Si")的地方再看到一條尖線. 基本上
所有其他的木管樂器它們的頻譜到了這樣高的音的時候也都是如此. 因此,豎笛,
長笛,雙簧管....等在最高音域所發出的聲音音色都很接近.

這裡我還得補充一點:即使對好的豎笛演奏者而言,其所發出的聲音的頻
譜通常到了超過5000 Hz的地方就會被切掉不見.也就是說在豎笛管身內超過5000
Hz頻率的振動大小已經小的可以忽略.而5000 Hz對我們的耳朵來說也變成了一個
魔術數字.關於這點,我們以後會再說明.

以上這些資料主要是參考A. H. Benade先生(核子物理學家,而且可能也
是二十世紀最具有影響力的木管樂器音響學的研究者)所寫的一本有趣的書,而對
於豎笛各個音域的範圍的部分,請參考Jack Brymer先生所著的"The Clarinet"一
書,或是Collin Lawson先生所主編的"The Cambridge Companion to the Clari-
net"一書.
(Tony曰:Brymer和Lawson都是當代英國豎笛大師, 也都有相當多關於豎笛的著述
.不過,前者是比較偏相豎笛演奏或樂團的經驗而後者則比較多關於古豎笛或是古
豎笛音樂的研究)

下次我們將從更定性上的方面來"看看"頻譜上音色的變化. 而這是俄亥
俄州立大學的James Pyne先生所做的實驗研究.

陳宣毅

=========================================================================

A Real Clarinet -- Simplified Version

What is a clarinet? (again!)

Let me answer this question in a more practical way, if you play
middle C (please understand that for a Bb clarinet this is actually a
concert Bb) on a clarinet first, then try to produce the next harmonic,
you find yourself playing the G which is a perfect twelfth, then high E
(a major sixth above previous G), .......
On the other hand, if you are playing a flute or oboe or saxophone,,
you find yourself playing C, C (an octive), G (a perfect fifth),....

That's the conclusion from my previous paragraph on an ideal clarinet.



I have to introduce many things that many of you already know. However,
there seems to be no other choice for me but to explain them clear before
we move on.

The sound of any instrument is actually very complex, otherwise they
should sound similar to us. To analyze the sound of a clarinet, it is
best to study the power spectrum of its sound.

So, what is "power spectrum"?

The sound from a clarinet can be thought as a combination of many sound
waves with single frequencies. The power spectrum tells us the
contribution of the sound from each single frequency. If the
contribution from frequency 440Hz is large, there is a peak around 440Hz
in the power spectrum.


Let's analyze the sound of a clarinet by using a machine that can give
us the power spectrum of a sound.

Now, if you play a sound in the middle C which is the lowest C that you
can play on a clarinet, the power spectrum shows a large peak at the
frequency which corresponds to the pitch of C, then there are peaks which
have frequencies 3, 5, 7,... times of that peak. This is what we expected
for a closed pipe instrument. However, there are some small peaks around
frequencies which are 2, 4, 6,.... times of that C. This tells us that a
real clarinet is not the same as the perfect model that I mentioned last
time. It is not a perfect "close pipe" instrument. Similiar shape of
power spectrum can be found through out the chalumeau register for a
clarinet. As a result of the lack of contributions from frequencies 2, 4,
6,... times of the first harmonic, the sound of clarinet in this register
is unique, and this is the characteristic of a clarinet.

Next, play a sound which is a perfect twelfth above the middle C. It is
a G, of course. Fingering of this note is the same as the middle C except
you have to add the register key to make the sound happen easier. This
is a note in the range of "clarion register". The power spectrum has
changed qualitatively from those in the chalumeau register. Of course the
peak that corresponds to the lowest frequency is that for the note G, but
the even harmonics are not small anymore. The even harmonics are smaller
than the odd ones but not by a lot. This is true for all notes in the
clarion register, i.e., from B (for Bb saporano clarinet, this is 440Hz)
to high C.

"Wait a minute!" you may want to say, "I can tell that is a clarinet
even you just say the spectrum has changed qualitatively."

Well, you just told me how good human ears are. We can tell by a tiny
difference of the power spectrum of the sound that somebody is playing a
clarinet, not a flute, or saxophone.

How about the next register?

Basically there are only 2 peaks, at most 3 peaks that you can see from
the power spectrum. If you play a high E, then you will find a peak at
double high E, then another one at double high B. This is basically the
same for all other woodwind instruments. Hence, clarinet, flute, oboe,...
can sound similar for altissimo notes.

I have to add one more point: The power spectrum of the clarinet tone
is usually cut at frequency of about 5000Hz for a good player. That
is, the vibration for frequency higher than 5000Hz is small inside a
clarinet tube. 5000Hz turns out to be a magic number for our ears, too.
I will come back to that later.


The above material is mostly based on interesting books by A. H.
Benade, a nuclear physicist and perhaps the most influential woodwind
acoustic researcher of the 20th century. For the range of different
registers for a clarinet, please check on "The clarinet" by Jack Brymer,
or "The Cambridge Companion to the Clarinet" ed. by Collin Lawson.


Next time a qualitative way of "seeing" the tone color from the power
spectrum will be described, which is an experimental work done by James
Pyne of Ohio State University.




Hsuan-Yi Chen




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