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Sorry for the mass mailing, friends... but I thought you would be especially
interested in this site, see email attached.
http://www.phys.unsw.edu.au/~jw/saxacoustics.html Paul Coats \\-- Link to
Paul's articles from Home page of "Sax on the Web": http://www.saxontheweb.net
or directly to Paul's articles at: http://www.saxontheweb.net/Coats/ Listen to
Paul's MP3's at: http://briefcase.yahoo.com/tenorman1952 and view photos.
\\--- mail_boundary --- [ Attachment content not displayed ]

--- In MouthpieceWork@yahoogroups.com, Paul Coats <tenorman@t...> 
wrote:
> Sorry for the mass mailing, friends... but I thought you would be
> especially interested in this site, see email attached.
> 
> http://www.phys.unsw.edu.au/~jw/saxacoustics.html
> 
> Paul Coats
> 
Paul-

Neat article and explains why the first octave sounds different from 
the second and third octave. I wonder if some manufactures have 
figured out how to create a sax with more even order harmonics in 
the first ocatve? 

Bill

I printed out the Intro to Sax Acoustics pages and read through them 
again today. In the "Playing softly and loudly" section, one aspect 
is bugging me.  According to the air flow vs pressure curve, as we 
blow harder and louder, the average air flow decreases.  

This is counter to what (I think) most player percieve.  In the 
extreme, I do experiance the reed closing off.  I even experiance the 
partial closing off when I approach this point.  But I do not 
percieve that playing softly requires more air that playing loudly.  
The exception would be that breathy sub-tone playing.  I'm not sure 
that that mode is depicted on the curve.  I recall reading somewhere 
in Benade's book that that is a different mode with an altered curve.

When playing soft on clarinet and soprano sax, I have so much air 
left over that I have to vent some out like oboe players do.

Anyone have insight as to how to make physical sence out of this 
parody?  

Keith:

Yes, I phrase differently on soprano sax, and often exhale at the end of
long passages, and sucking in fresh air.

As for the rest of your question:

We make the mistake of assuming that the harder we blow, the more air we
move.  That is not necessarily so.  We can only feel the pressure we use
to move the air.  We do not directly notice or measure the air volume we
move, except in how often we suck in a fresh breath.

It seems that when playing softly, much of the air is slipping past the
reed.  But when the sax�s air column begins to really excite the reed
well, the whole system becomes more efficient, and more of the energy is
making tone, instead of slipping past the reed.

Let us look at how and why the reed vibrates, and how it excites the air
column.  (This is the Reader�s Digest version, so bear with me.)

Imagine water in a bathtub.  You disturb the water on one end of the tub
with your hand, and a wave of water moves from one end to the other,
raising the water level on the other side, and lowering it on the side
where the disturbance occurred.  The water wave hits the other side of
the tub, and is reflected back, and this water wave goes back and forth
until it dies out.  It WILL die out from frictional losses, that is,
unless you continue to add energy to the system by continuing to disturb
the water at just the right time... just as the peak of the wave reaches
your hand in the water.

If you don�t time the movements of your hand to coincide with the
returning waves, there will soon be chaos in the water and the
oscillation will die out.  So, there needs to be some sort of regulating
device to make the disturbance happen at the right time.  For the
woodwind instrument, that device is the mouthpiece and reed.

The player blows on the mouthpiece/reed, disturbing the air column
contained in the saxophone.  To make this air move, the air pressure is
higher in his mouth than in the horn.  This is not much of a pressure
difference, but it must occur or the air would not move.  A puff of air,
which is a higher pressure than in the bore, goes through the reed and
mouthpiece, and travels as a wave down the horn.  It leaves in its wake
a low-pressure area, just as the water wave in the bath tub left behind
a low area of water.

The pressure is held constant in the player�s mouth, and the pressure
drops in the sax as the high pressure moves away.  It finally reaches a
point where the pressure differential is enough to overcome the
springiness of the reed, and the reed blows shut on the mouthpiece (or
is sucked shut by the low pressure inside the mouthpiece).

Some of the energy of this wave is absorbed by the pads and becomes heat
(thus the need for resonators for more efficiency).  Some energy is
frictional loss with the side walls of the bore.  And some leaks out of
the horn at the open end as the sound we hear.

The high pressure portion of the wave hits the bell, or first open tone
hole, and is bounced back, or reflected, just as the water wave was
reflected by far side of the tub.  The high pressure travels back up the
air column and finally reaches the reed.  Now, the pressure is high
enough, as compared to the pressure inside the mouth, such that it is
about equalized.  Now the low air pressure differential is not as strong
and releases the reed, and its springiness is enough to allow it to
open.   (I will come back to this later, making another point or two.)

Since the reed is open, it allows the introduction of another puff of
air, and the cycle repeats.  Energy from the player�s airstream is added
to the system at the same rate as it leaks away in the system, and the
tone is sustainable.

At low sound volumes the reed oscillates, lightly slapping the facing,
but only remaining fully closed for a small percentage of time.  There
is not much air pressure difference between the player�s mouth, and the
air pressure inside the sax, and the negative pressure portion of the
wave is only strong enough to hold the reed shut a small percentage of
the cycle.  (Remember this!!!)  Since the wave is moving smoothly up and
down the body of the sax, it approximates a sine wave, or a series of
sine waves both odd and even in number, making the sax tone.

The reed spends more time in transit from fully open to fully closed.
In relation to the amount of sound being produced, more air is used, as
the reed is open a greater percentage of time for each oscillation
period.  Some of the air is passing through in the time period needed to
sustain the oscillation (otherwise a tone would not be produced), and a
small amount of air is leaking through, since the reed is not fully
closed) during the time period when there is a negative air pressure in
the air column at the mouthpiece.  This actually �fights� the
oscillation, and tends to damp it.  So this air is wasted, from an
efficiency point of view.

As the pressure is increased, and the player plays louder, the low
pressure portion of the air column is stronger in relation to the air
pressure in the mouth.  This causes the reed to stay fully closed for a
longer period of time, finally getting to fully closed for 180 degrees
(50% of the time) at a high volume.  What air is used is all used at the
correct time to enhance the wave.  Maximum efficiency.

However, the reed being closed for 180 degrees (or 50% of the time) of
the cycle causes that negative half of the wave to be more like a square
wave, which is composed of odd overtones.  So, odd overtones are
enhanced.  As the player plays still louder, this effect is enhanced and
heard as more �edge�.  Fortunately for us, this edge is composed of high
frequency components that fall in the correct range where the ear can
hear it easily.

This is why the tone of the sax, and other woodwinds, changes as the
volume increases.

Remember what I said about the differential between the high pressure in
the mouth, and the low pressure in the sax being high enough to overcome
the springiness of the reed, and closing the reed?  If the reed is very
compliant, that is, low in springiness (a �#1 reed�), this happens at a
relatively low pressure inside the mouth.  (The pressure inside the sax
is always going to be very nearly the same as outside air pressure.)
So, the reed is made to move with less air pressure from the player.  It
reaches maximum movement (180 degree of closure, and thus maximum
efficiency) sooner than a stiffer reed.  It produces edge sooner, but is
easier to play.  And this is exactly what we see with a soft reed.  But
the player soon reaches a point where he can put no more air through the
horn.  What a beginner does is open his embouchure in an effort to let
more air through the horn, and he goes flat.  What an older player does,
he gets a more open mouthpiece or a harder reed.

Let�s look at the other possibility� changing to a harder reed.  With
the harder reed, more air is put into the horn before the reed reaches a
point of 180 degree closure.  Some band directors make their students
use 3 � Vandorens to get a �darker sound� from their band� one size fits
all.  You hear many of these students with an airy tone.  We all know
that too hard a reed produces a dull, airy tone.  And now we know why.
It is very difficult to reach a point where it opens and closes well.
With a hard reed they will have to use a mouthpiece with a narrow tip
opening, which is easier as the reed does not have to move very far to
open and close.

Let�s also consider facing contour� a smooth curve (arc of a circle)
facing will allow the reed to smoothly open and close.  The tone is less
edgy at all volumes.  The contour allows the reed to follow the air
pressure of the wave, and can play better at low volumes.

With the flat facing, where there is short radius at the break, and a
long flat region out to the tip, as some clarinet mouthpieces are made,
when the reed closes, it closes all at once.  An approximation of this
is the long facing with narrow tip opening.  This makes both sides of
the wave more square.  This works better on the clarinet, as the
clarinet bore produces only odd overtones, which form a square wave.

The saxophone bore produces both odd and even overtones (sawtooth wave),
smoothly ramping open and closed at low volumes.  At higher volumes, the
wave diagram ramped smoothly on one side (corresponding to the open
portion of the reed travel) and is more nearly vertical on the other
side (corresponding to when the reed is closed for 180 degrees or 50% of
the time).  This is why a smoothly curved facing is better on the
saxophone, as the reed closure and opening can more easily follow the
waves which are being produced.

Let�s go play with the bath water again� if we smoothly wave our hand at
one end, and synchronize movement with the wave in the tub, we can most
efficiently add energy to the system.  If we just slap the water with a
jerky movement as the wave peaks, we can still keep the wave moving in
the tub, but not as efficiently.  We introduce turbulence and little
subwaves (overtones), and some work for us, some against us, but we are
not using our energy most efficiently.

I hope this helps you visualize how the sound wave moves in the
saxophone, and how it inter-reacts with the reed and the facing of the
mouthpiece.

Paul



Keith Bradbury wrote:

>  I printed out the Intro to Sax Acoustics pages and read through them
> again today. In the "Playing softly and loudly" section, one aspect
> is bugging me.  According to the air flow vs pressure curve, as we
> blow harder and louder, the average air flow decreases.
>
> This is counter to what (I think) most player percieve.  In the
> extreme, I do experiance the reed closing off.  I even experiance the
> partial closing off when I approach this point.  But I do not
> percieve that playing softly requires more air that playing loudly.
> The exception would be that breathy sub-tone playing.  I'm not sure
> that that mode is depicted on the curve.  I recall reading somewhere
> in Benade's book that that is a different mode with an altered curve.
>
> When playing soft on clarinet and soprano sax, I have so much air
> left over that I have to vent some out like oboe players do.
>
> Anyone have insight as to how to make physical sence out of this
> parody?
>
>
>                    Yahoo! Groups Sponsor
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>
> Got a Mouthpiece Work question?  Send it to
> MouthpieceWork@yahoogroups.com
>
> Visit the site at http://groups.yahoo.com/group/MouthpieceWork to see
> the Files, Photos and Bookmarks relating to Mouthpiece Work.
>
> To see and modify your groups, go to http://groups.yahoo.com/mygroups
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

--
Link to Paul's articles from Home page of "Sax on the Web":

  http://www.saxontheweb.net

or directly to Paul's articles at:

  http://www.saxontheweb.net/Coats/

Listen to Paul's MP3's at:

                http://briefcase.yahoo.com/tenorman1952

and view photos.

Thanks Paul for that well-composed reply.  I'm still not sure why I am able
to hold a soft note for a longer time than a loud one.  I run out of breath
sooner at loud levels (below the close-off pressure).

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At low levels, from the amount of energy you put in, compared to the
sound coming out, actually, you should be using far less air.

Let me put it this way� if you drive your car at 100 mph, and at that
speed, get 15 miles per gallon, and then drive at only 10 mph, yes, you
are driving slower, and using gas at a far slower rate BY TIME.  But if
you are only getting 10 miles per gallon at 10 miles an hour, you are
less efficient.

Paul


Keith Bradbury wrote:

>  Thanks Paul for that well-composed reply.  I'm still not sure why I
> am able
> to hold a soft note for a longer time than a loud one.  I run out of
> breath
> sooner at loud levels (below the close-off pressure).
>
> __________________________________________________
> Do you Yahoo!?
> Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!
>
> http://platinum.yahoo.com
>
>                    Yahoo! Groups Sponsor
                        ADVERTISEMENT


>
> Got a Mouthpiece Work question?  Send it to
> MouthpieceWork@yahoogroups.com
>
> Visit the site at http://groups.yahoo.com/group/MouthpieceWork to see
> the Files, Photos and Bookmarks relating to Mouthpiece Work.
>
> To see and modify your groups, go to http://groups.yahoo.com/mygroups
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

--
Link to Paul's articles from Home page of "Sax on the Web":

  http://www.saxontheweb.net

or directly to Paul's articles at:

  http://www.saxontheweb.net/Coats/

Listen to Paul's MP3's at:

                http://briefcase.yahoo.com/tenorman1952

and view photos.

I'm still where I started:  There is real stuff going on that is not
explained by the mouthpiece & reed flow vs. pressure curve.

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