Mujitsu and Tairaku's Shakuhachi BBQ

World Shakuhachi Discussion / Go to Live Shakuhachi Chat

You are not logged in.


Tube of delight!

#1 2010-03-07 16:27:39

airin
Member
From: Vancouver, BC, Canada
Registered: 2008-10-17
Posts: 303
Website

Back Pressure - what and why?

What exactly is back pressure as it relates to shakuhachi and why is it desirable?

Offline

 

#2 2010-03-07 19:54:52

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Back Pressure - what and why?

airin wrote:

What exactly is back pressure as it relates to shakuhachi and why is it desirable?

Given that back-pressure in the shakuhachi is created by a tapering bore, these two links might be instructive:

                http://www.navaching.com/shaku/bore.html

                http://www.navaching.com/shaku/taper.html

Last edited by edosan (2010-03-07 19:55:33)


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

Offline

 

#3 2010-03-08 01:45:57

radi0gnome
Member
From: Kingston NY
Registered: 2006-12-29
Posts: 1030
Website

Re: Back Pressure - what and why?

It's easier with some shakuhachi than others, but don't you sort of have to create the back pressure with your embouchure? When I first got my Taimu I thought it had very little back-pressure, but after playing it for a while I realized a lot of that first impression was that I didn't know how to blow it correctly.

The more back pressure the easier it is to circular breath, although it's not a technique typically used on shakuhachi. Didjeridu, an instrument that's typically played with circular breathing, is more trumpet-like and has tons of back-pressure. One unusual thing about it is that I understand that if you have someone blow some smoke near the bell while you're playing that the smoke gets drawn up into the tube. I'm not sure if that's a characteristic of it being a trumpet-like instrument or if it's a characteristic of the dimensions of the tube.

Where's Toby when you need him?...


"Now birds record new harmonie, And trees do whistle melodies;
Now everything that nature breeds, Doth clad itself in pleasant weeds."
~ Thomas Watson - England's Helicon ca 1580

Offline

 

#4 2010-04-01 14:37:45

Ryan Sullivan
Member
From: Tallahassee, FL USA
Registered: 2010-04-01
Posts: 20

Re: Back Pressure - what and why?

I am no degree earning scientist or anything, but here goes my understanding of backpressure.

Back pressure is inherent to the bore. Back pressure is directly related to aspect ratio ie. ratio of the bore's cross-sectional area to the bore's length. It does not have to be a tapering bore. A taper will affect the back pressure, but so will anything that you do to the bore. A bore is like a river, speeding up in shallow spots and slowing down in deep spots. What we hear and feel is a cumulative affect of all sorts of little things happening at the speed of sound.
Back pressure comes from resistance. Using the same strength of breath..If you try and blow into the open air, you get no resistance; if you try to blow into something short and fat you get a little resistance; if you try and blow through something long and narrow, you get a lot of resistance. This is because of the mass of air working against your breath. Have a bunch of people (air molecules) stand side by side (wide/short bore) and push (directed air stream) through one of them. No problem getting through (low resistance). Now have a bunch of people (air molecules) stand front to back (narrow/long bore) and try to push through. Tough to do (high resitance). The higher the aspect ratio--narrower cross-sectional area per unit of length, the more back pressure a bore will have. This is true for a bore whether tapered or not. If a flute does not have any back pressure, it is not a flute at all because it will not play. You will just be blowing air straight through.
In order for a pitch to be produced, a system must be set up in which pressure and vacuum (crests and troughs, nodes and antinodes, etc) alternate REPEATEDLY. When we say "A" is 440 Hertz, we mean "my mind experiences a particular phenomenom when air is "pushed" and "relaxed" 440 times in a single second. Without this same event happening 440 times in a second we will not hear "A". It is the back pressure that allows a crest of air pressure to reflect back as a trough of air vacuum. Without this event, there is nothing to repeat 440 times. This, then, leads into why a didj draws smoke up the bore--it really only draws smoke up the bore for a portion of a cycle (when the didj is vacuumizing) and blows smoke out the other portion of the cycle (when the didj is pressurizing). A flute does the same thing at both the foot and the head. Didjs tend to be Much longer than flutes, so their wavelength is longer, therefore the amount of time between pressure and vacuum is longer allowing the time smoke is drawn into the bore to be more visibly noticeable.
The issue of embouchure in back pressure seems to be one of "opitmization". Resonance is key to sound. Without resonance, there is no musical pitch. You can have strong resonance or weak resonance, but there must be resonance. Resonance occurs when the air which is moving into the bore is moving at such as speed as to reach its terminal point at the EXACT SAME TIME as the pressure moving into the bore reaches its terminal point, and when the air which is moving out of the bore reaches its exit point at the EXACT SAME TIME the vacuum exiting the bore reaches its terminal point. Thus, to have STRONG resonance, you must be hitting a very PRECISE speed with your breath, the speed determined by the flute. Now, a flute has a degree of "error" in which your breath speed can be slightly off the speed needed for max resonance and yet still produce a musical pitch. However, the sound quality will be altered.
Now, realize that not all of the air/pressure is reflected back into the system, some of it continues out of the flute bore. And since you are literally an extension of the bore, some of it extends into you. Your body: mouth, sinuses, throat, chest, etc. are resonators coupled to the air column of the flute bore like the body of the violin is coupled to the strings. So, if you can get your body's geometry to suit the pitch you are attempting to play, the resonance will be enhanced and you will get closer to what Masayuki Koga calls "Master Sound" (not that I am getting that or anything:>) Nail a violin, guitar, whatever, string to the wall and hear how poorly it sounds. Then play a string that is attached to a well shaped violin, guitar, whatever.
Oh, the most important thing is     HAVE FUN!!


"There are connections we cannot even see, my friend"

Offline

 

#5 2010-04-01 15:36:41

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Back Pressure - what and why?

Very nicely done, sir.


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

Offline

 

#6 2010-04-02 10:29:46

airin
Member
From: Vancouver, BC, Canada
Registered: 2008-10-17
Posts: 303
Website

Re: Back Pressure - what and why?

That was an excellent explanation - thanks!

Offline

 

#7 2010-04-02 11:58:32

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

Ryan Sullivan wrote:

I am no degree earning scientist or anything, but here goes my understanding of backpressure.

Back pressure is inherent to the bore. Back pressure is directly related to aspect ratio ie. ratio of the bore's cross-sectional area to the bore's length. It does not have to be a tapering bore. A taper will affect the back pressure, but so will anything that you do to the bore. A bore is like a river, speeding up in shallow spots and slowing down in deep spots. What we hear and feel is a cumulative affect of all sorts of little things happening at the speed of sound.
Back pressure comes from resistance. Using the same strength of breath..If you try and blow into the open air, you get no resistance; if you try to blow into something short and fat you get a little resistance; if you try and blow through something long and narrow, you get a lot of resistance. This is because of the mass of air working against your breath. Have a bunch of people (air molecules) stand side by side (wide/short bore) and push (directed air stream) through one of them. No problem getting through (low resistance). Now have a bunch of people (air molecules) stand front to back (narrow/long bore) and try to push through. Tough to do (high resitance). The higher the aspect ratio--narrower cross-sectional area per unit of length, the more back pressure a bore will have. This is true for a bore whether tapered or not. If a flute does not have any back pressure, it is not a flute at all because it will not play. You will just be blowing air straight through.

I gotta jump in here because to my experience flutes have no resistance or back pressure. It is all manufactured at the embouchure. The proof is to put your mouth completely over the blowing end and breath through the instrument. You will feel no resistance because there isn't any. Oboes have lots of back pressure. Bassoons also. Clarinets too. Saxophones a little less. All for the same reason, the aperture they are blowing into is too small to take all the air  being blown. We have to create this ourselves with flutes. It's possible we have different definitions of what backpressure or resistance is.


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

#8 2010-04-02 14:29:19

Ryan Sullivan
Member
From: Tallahassee, FL USA
Registered: 2010-04-01
Posts: 20

Re: Back Pressure - what and why?

Thanks for the insightful comment Jim Thompson. (How do I put previous posts in a block of quote?)
It seems that back pressure must be manufactured, at least in part, by the embouchure. If you blow through a sax, oboe , clarinet, etc. without the reed attached, you can blow through just the same as a flute. Or even if you leave the reed on and blow softly with lips relaxed. And, if you blow through the end of a flute with pursed trumpet embouchure, you'll experience all sorts of back pressure and a sound much different than if you played it like a flute.
It seems to me, that any given bore has a certain potential for back pressure, and there are many ways to acess that pressure. When I put a shakuhachi to my lips and sing a resonant pitch into it, I feel back pressure.
I personally do not believe that back pressure only exists at the embouchure. I have played didjeridoo in a manner such that I have felt the pressure wave travel down the bore, reflect at the other end, "hit me in the face", travel down my wind pipe, reflect back into the didj, and on and on.
However, I can also circular breathe without any external instrument at all: simply by keeping back pressure with my lips.
And we can all play a basic scale with only buzzing lips, but the sensation is quite different when there is a trumpet to push back.

How do you explain pressure nodes/antinodes, overtones, resonance, and the general functioning of flutes without the bore having back pressure?
Also, how do you explain flutes of long/narrow bore giving more...well....back pressure than short/wide flutes?
If it is only our embouchure, wouldn't we be able to make exactly the same sounds regardless of the bore. Without the bore playing back, what is there to affect the sound?


"There are connections we cannot even see, my friend"

Offline

 

#9 2010-04-02 16:15:16

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Back Pressure - what and why?

Ryan Sullivan wrote:

How do you explain pressure nodes/antinodes, overtones, resonance, and the general functioning of flutes without the bore having back pressure?
Also, how do you explain flutes of long/narrow bore giving more...well....back pressure than short/wide flutes?
If it is only our embouchure, wouldn't we be able to make exactly the same sounds regardless of the bore. Without the bore playing back, what is there to affect the sound?

Ryan,
You can get a quote of a post (or any part of that quote) by clicking on "Quote" at the lower right of any given post, whereupon
you'll get the quote at the top of a new message box for you to write your response into. You can delete any part of the quote you
like, as I did here. Just make sure you leave the tags (in brackets) at each end of the quote undamaged.

If you want to see what the quote/post looks like before committing it, you can click on 'Preview' below, and see how it plays on
the screen before hitting 'Submit'.


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

Offline

 

#10 2010-04-02 18:54:50

Musgo da Pedra
Member
From: South of Brazil
Registered: 2007-12-02
Posts: 332
Website

Re: Back Pressure - what and why?

Anything in the bore that make your wind stop and come a ittle back, that make your wind flow back until you feel it in you nose.

It's really nice to feel because it holds you while the notes, pitches  or whatever, and makes you explode BACK in the tube of the holding backing thing.

Very suble thing on our Palmito Stick.


Omnia mea mecum porto

Offline

 

#11 2010-04-02 21:16:11

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

Ryan Sullivan wrote:

Thanks for the insightful comment Jim Thompson. (How do I put previous posts in a block of quote?)
It seems that back pressure must be manufactured, at least in part, by the embouchure. If you blow through a sax, oboe , clarinet, etc. without the reed attached, you can blow through just the same as a flute. Or even if you leave the reed on and blow softly with lips relaxed. And, if you blow through the end of a flute with pursed trumpet embouchure, you'll experience all sorts of back pressure and a sound much different than if you played it like a flute.
It seems to me, that any given bore has a certain potential for back pressure, and there are many ways to acess that pressure. When I put a shakuhachi to my lips and sing a resonant pitch into it, I feel back pressure.
I personally do not believe that back pressure only exists at the embouchure. I have played didjeridoo in a manner such that I have felt the pressure wave travel down the bore, reflect at the other end, "hit me in the face", travel down my wind pipe, reflect back into the didj, and on and on.
However, I can also circular breathe without any external instrument at all: simply by keeping back pressure with my lips.
And we can all play a basic scale with only buzzing lips, but the sensation is quite different when there is a trumpet to push back.

How do you explain pressure nodes/antinodes, overtones, resonance, and the general functioning of flutes without the bore having back pressure?
Also, how do you explain flutes of long/narrow bore giving more...well....back pressure than short/wide flutes?
If it is only our embouchure, wouldn't we be able to make exactly the same sounds regardless of the bore. Without the bore playing back, what is there to affect the sound?

Ryan,
    I think we may be getting our apples and oranges mixed up.  The internal factors of the bore have a tremendous effect on the sound of the instrument. I know the term  choke point  sort of implies a backed up air stream but I wonder if the term refers to the way vibrations pass through rather than the amount of air allowed through. All the examples you cited are all examples of back pressure created by pursed lips whether the lips are buzzing (as on a trumpet or didj) or not. You didn't rebut my point about putting your mouth completely over the end and inhaling and exhaling. There is absolutely no resistance. If you were 20 feet tall and 2000 lbs. maybe you would find some resistance. You may feel all kinds of resonances and vibrations permeating your body and the environment but the only back pressure is created by the pursed lips. Unpurse your lips and there is no back pressure.


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

#12 2010-04-03 09:19:18

Ryan Sullivan
Member
From: Tallahassee, FL USA
Registered: 2010-04-01
Posts: 20

Re: Back Pressure - what and why?

Jim Thompson wrote:

I think we may be getting our apples and oranges mixed up.  The internal factors of the bore have a tremendous effect on the sound of the instrument. I know the term  choke point  sort of implies a backed up air stream but I wonder if the term refers to the way vibrations pass through rather than the amount of air allowed through. All the examples you cited are all examples of back pressure created by pursed lips whether the lips are buzzing (as on a trumpet or didj) or not. You didn't rebut my point about putting your mouth completely over the end and inhaling and exhaling. There is absolutely no resistance. If you were 20 feet tall and 2000 lbs. maybe you would find some resistance. You may feel all kinds of resonances and vibrations permeating your body and the environment but the only back pressure is created by the pursed lips. Unpurse your lips and there is no back pressure.

I agree that if you set your breath up in such a way as to blow gingerly through a flute, there will be no experience of back pressure. The same thing can be seen with water: if you lightly step into water, there is no resistance, you simply dip right in. However, if you jump out of a 40 foot tree into the water, there is hell of resistance. This is brought about by the momentum of the fall (the airstream) but the fall is not solely responsible for the resistance.
Think about the fact that the air you are falling into before the water has less resistance than the water itself, and if you were to jump into the ground instead of water, there would be much more resistance. If resistance was based solely on the jump, it wouldn't matter what medium we fell through.

I believe that there is not only back-pressure latent in a flute, there is also forward-vacuum. Keep in mind that flutes do not always allow our air to enter into their inner zone. For half of the cycle, the pressure inside the bore is directing our airstream out of the flute. Then, for the other half, the vacuum inside the bore is drawing our air in.
I am saying that we Do contribute to back pressure just as Jim Thompson is saying, but it seems to me, that the flute has a very big role in the amount of pressure/vacuum exercised.
Think about resonance: we can "lip" a flute out of strong resonance by adjusting our embouchure, but there is a limit to this ability and that is based on the particular instrument. This is why saxaphonists have different mouthpieces, some "bend pitch" more than others.
On the other hand, when we approach strong resonance, the flute brings our lips into tune with it.
I am merely proposing that back pressure is not a one way street.

Last point before I go--Choke point...does it deal with "vibration" passed through or "air" passed through.
I think that depends on whether the choke point lies on a flow node, pressure node, or somewhere in between.
And this too is something latent within the flute, AND we have some control over. Play and pitch and then overblow into the next range, you will be changing the location of the activated nodes. BUT you can only overblow to pitches allowed by the pressure/vacuum system of whatever specific flute you are playing.
Thanks for the time
off to the beach


"There are connections we cannot even see, my friend"

Offline

 

#13 2010-04-03 10:51:54

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

Ryan,
      Step away from the University! I repeat. Step away from the University and run for your life. You can come stay here by the ocean. We are deprogrammers.


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

#14 2010-04-03 21:57:15

Ryan Sullivan
Member
From: Tallahassee, FL USA
Registered: 2010-04-01
Posts: 20

Re: Back Pressure - what and why?

Jim Thompson wrote:

Ryan,
      Step away from the University! I repeat. Step away from the University and run for your life. You can come stay here by the ocean. We are deprogrammers.

HA! Dude, I ran away long ago.


And for my friend Jon-

We did not complicate anything. I didn't invent the universe.



Enjoy the day

oh....how do i do the "grey quote box" for multiple quotes?


"There are connections we cannot even see, my friend"

Offline

 

#15 2010-04-03 22:08:13

Tairaku 太楽
Administrator/Performer
From: Tasmania
Registered: 2005-10-07
Posts: 3222
Website

Re: Back Pressure - what and why?

Luckily we have a resident shakuhachi scientist on the forum. Calling Dr. Toby! Dr. Toby please!


'Progress means simplifying, not complicating' : Bruno Munari

http://www.myspace.com/tairakubrianritchie

Offline

 

#16 2010-04-03 22:27:32

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

Good idea Brian! Maybe he can simplify this for us.


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

#17 2010-04-04 10:36:29

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Back Pressure - what and why?

Jim Thompson wrote:

Good idea Brian! Maybe he can simplify this for us.

Yeah, right.......


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

Offline

 

#18 2010-04-04 10:58:21

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

Ed'o and Brian,
     Maybe Chris has some suggestions on how we can agitate this beef. ( I really need to learn to make those smiley faces so people don't get the wrong idea. All I get is the actual marks I enter).


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

#19 2010-04-04 12:14:29

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Back Pressure - what and why?

Jim Thompson wrote:

Ed'o and Brian,
     Maybe Chris has some suggestions on how we can agitate this beef. ( I really need to learn to make those smiley faces so people don't get the wrong idea. All I get is the actual marks I enter).

Poor man, living in the dark ages: at the bottom of this page, sort of lower leftish, you'll see a link called 'Smilies'.

If you click on that, you'll find out more than you want to know about how to implement 'em.


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

Offline

 

#20 2010-04-04 14:39:22

Jim Thompson
Moderator
From: Santa Monica, California
Registered: 2007-11-28
Posts: 421

Re: Back Pressure - what and why?

big_smile


" Who do you trust , me or your own eyes?" - Groucho Marx

Offline

 

Board footer

Powered by PunBB
© Copyright 2002–2005 Rickard Andersson

Google