the myth of "fast air"

Discussion in 'Trumpet Pedagogy' started by rowuk, May 2, 2008.

  1. rowuk

    rowuk Moderator Staff Member

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    I read this from time to time and question the concept.

    If I analyse the process, it normally involves raising the tongue creating more of an "eeh" syllable instead of a "ooh". We use the garden hose analogy - put your thumb over the end of the hose and the water sprays farther. While it is true that the water does travel farther, the stream is much "thinner", and that is NOT what I hear from world class players using this "technique".

    So what is happening? Our tongue is NOT a thumb covering the garden hose, our lips have that function and they compress to play higher notes. When we compress the lips, we need more "air pressure" to blow them apart (not velocity or speed) but our breathing doesn't change so the additional pressure does not come from there.

    I found the answer in a horn loudspeaker developers course. Our mouth is a chamber between the pump (breathing apparatus) and embouchure. That oral volume is greatest when we articulate with a "Tooh" as the tongue is low in the mouth, the cavity above and below the tongue is added together. That cavity introduces an inefficiency which would lower the pressure that the lips see. The cheeks are also elastic when relaxed additionally making the chamber "softer".
    When we raise the tongue, we at least partially seal off the lower part of that cavity (between the sides of the tongue and the teeth), decrease the size of the upper cavity providing a more efficient path for the air to flow. That increase in efficiency is in air pressure not velocity and not "thinner". THAT is what I hear when listening to world class players.

    Paul Klipsch published several papers on his design of the Klipschorn. The woofer part of the horn uses a chamber right in front of the speaker to modify its response. Trumpet players have a variable chamber.

    If you are still sceptical, let's finish the garden hose analogy:
    the pump is our breathing, the hose our throat, I'll let the thumb be the tongue and we spray the water into a bucket with a hole in the bottom (our mouthpiece). I can spray fast water into the bucket, what drips out of the bottom has NOTHING to do with that spray speed.

    We can add another level of complication, we seal the hose and the bucket off at the top (like our lips and the mouthpiece rim). We spray fast water into the bucket, it still only drips out until the bucket is full and then the bucket of water starts fighting back - the hole at the bottom of the bucket (the mouthpiece throat) is the determining factor here, our spray velocity has been neutralized by the entire system. If the hole in the bucket is the same size as the hose diameter, water will pour out at the same speed as the open hose!

    With a trumpet, we have a much more complicated situation as the air doesn't really pass through the horn like that leaky bucket. The resonance of the horn also "fights" back further limiting velocity, but increasing "pressure" which aids the upper register.

    For all of you that were helped by the speed visualization, essentially you were not told the truth, but the end product - better upper register was the same. Maybe with this post we can start telling the truth and wonders of efficiency instead of the myth of velocity. Any additions or corrections are appreciated!!!!!!

    This would make an excellent theme for a doctorate! Any takers?

    I have further insite here, let's get some responses first!
     
    Last edited: May 2, 2008
  2. VetPsychWars

    VetPsychWars Fortissimo User

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    The mouth is also a resonant chamber, and we're modifying the size of that chamber, which will result in a change of the resonant frequency.

    I believe that is a factor as well.

    Tom
     
  3. oldlips48

    oldlips48 Piano User

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    Whoa, talk about a huge number of conditions and variables from player to player!.

    One thing I would add to the water-bucket analogy, Rowuk. Gases are compressible, liquids (from a practical viewpoint) are not. So if you were to duplicate the bucket experiment with air, you would find the airstream entering the bucket to just about match the pressure leaving the bucket, but there would be some compression of the air inside the bucket. You mentioned the elasticity of the cheeks, I think this would have quite an effect considering we're essentially pressurizing two gases (80% nitrogen, 20% oxygen) inside our mouths when we play.

    I agree also with the one chamber/two chamber analogy as to the placement of the tongue. Players (like me) that brace the inside of their lower lip with their tongue would also be reducing. the "chamber" size in their mouth.

    And all this is not even to mention mouth size, mouth shape, teeth size and placement, lip size and configuration.
     
  4. westview1900

    westview1900 Piano User

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    Dear Rowuk,
    I love your well thought out explanations. You have obviously studied this subject in depth. Would you say that the pressure increase or decrease directly affects the speed of the air?
     
  5. rowuk

    rowuk Moderator Staff Member

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    Oldlips,
    it is even more complicated. We are not talking about airflow as such because soundwaves are alternating (AC not DC as in the bucket example) in direction and there is a standing wave set up in the horn, players diaphragm to horn and room to diaphragm. We blow because that is the only way to get the lips moving until the resonant system takes hold, then the amount of air required to maintain sound in a reasonably efficient system becomes FAR less!

    The vibrating air particles that we create with our playing do not "travel" through the room like water in that bucket. They bump into the neighboring particles and there is even a slight loss of energy passed on with every motion. The compression in the mouth actually changes the speed of sound at the same time - ever talked after swallowing helium? The air that we breathe does not move at the speed of sound to the audiences ear. The air is pretty much static and the soundwaves flow through it..

    Yes the analogy of speed (fast air) is as wrong as wrong can be.
     
  6. NickD

    NickD Forte User

    Great thoughts here. I think it is even more complicated than we thought.

    The idea of a resonanting chamber behind a speaker (think Bose speakers, or ANY speaker cabinet for that matter) affecting the behavior of a speaker is solid, but we have to consider the mass of the speaker cone.

    There is a reasonable impedance match between the chamber behind the speaker and the the cone, so the effect of the chamber is perceivable.

    However, the mass of the lips is pretty high compared to the mass of air in the oral cavity. There is a huge impedance mismatch.

    In fact this has been written up by Dr. Thomas Moore, the science editor of the ITG Journal. I'll have to look it up (I'm not at home where my ITG archives are), but he wrote and article based on a set of experiments he did with artificial lips and a compressor driving them to energize a trumpet. He found minimal impact on the size of the box behind the lips on the playing behavior of the horn.

    Now, I don't have an opinion. Moore's article was provocative to me, as I use a TCE approach to playing the extreme upper register (my high gear embouchure). Tongue position is critical to me, but I don't see exactly why. I originally thought of the oral cavity as a secondary resonator added to the system and that by controlling its size, and hence resonant frequency I could affect the chages needed for the upper register. However, in light of Moore's article, I was trying to devlop some sort of "flow controlled valve" model for explaining why my use of the tongue in concert with the lips gets me the upper register I want.

    So, I'm still sorting this out.

    Here is a link to Moore's work. There is some REALLY interesting stuff. To his credit, as experiments bring new ideas to light, he changes his postiion. His ideas about bell vibrations are clearly different from what they used to be.

    Research

    More grist for the mill! I'll check back later.

    Nick

    PS: I want to get my DMA someday. Writing this up would be interesting assuming it hasn't been taken by the time I can sort out funding, sabattical and WHERE (U of I comes to mind, but I have no idea if I'd make the cut).
     
    Last edited: May 2, 2008
  7. NickD

    NickD Forte User

    Last edited: May 2, 2008
  8. rowuk

    rowuk Moderator Staff Member

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    Nick,
    I am not talking about the cabinet behind the cone on a free air speaker like Bose, AR, Polk or whatever. I am talking about reactance annulling of a speaker with a horn in front of it. In that case we have to take into account the pressure on both sides of the lips. The closer they are to one another, the less muscle that we need to keep the chops from falling into the cup. The chamber (oral cavity) can provide that variable reactance. This is why players can also use extremely shallow mouthpieces and not have their chops block the cup!

    Also of interest to you would be the effect of that chamber as a low pass filter. The larger the chamber, the less high frequencies are passed. That would translate to high tongue position = bright sound, low tongue = darker sound, something we all experience! This only works because we are talking about AC not DC.

    The efficiency that I mention is another aspect. Trumpets amplify most in their lower 2 1/2 octaves. That is based on the horn shape, length and bell to leadpipe size. Above that, the horn is significantly less efficient. Raising our tongue for higher notes increases efficiency making the overall response more even.

    In calculating the lip mass, we have to estimate how much of the lip is really moving. The lips do not vibrate like a guitar string, they open and close like a switch. Once the standing wave is set up, I suspect the moving mass is quite low. The rest of the lip only acts like the "suspension" or butyl surround on a loudspeaker.

    I guess the bottom line is that there is no "fast air". There is just the battle of air pressure in front of and behind the lips. That is easily backed up with the numbers, however complex. I have glued a little loudspeaker to a mouthpiece and let it play buzzing noises. The trumpet amplifies just like when it is being played with only the resonant node frequencies being the peaks. No air really has to "flow" at all, except to get our lips moving.
     
  9. rowuk

    rowuk Moderator Staff Member

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    I would say that any change in air "speed" would be neutralized by the resonant system. The only "speed" that changes is the speed of sound for the lips based on the pressure behind and in front of the lips. They vibrate (open and close) based on that pressure state.

    Here is something to maybe help the visualization:
    Play a low C as loud as you can - count the seconds. Then do the same thing 2 octaves higher. If your air is faster, you run out of air sooner, but it just ain't happening. You can hold the high C out MUCH longer!
     

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