Experience gap acoustics and airflow

Discussion in 'Trumpet Discussion' started by [email protected], May 15, 2014.

  1. feedback@stomvi-usa

    [email protected] Piano User

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    Here is a video demonstrating how you can experience the affect adjusting the gap has on airflow and acoustics. You will be able to check out how changing the gap changes the sound, intonation, slotting, and acoustic backpressure.

    http://youtu.be/sMzz0x-Eg9I
     
  2. rowuk

    rowuk Moderator Staff Member

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    A discussable point for sure.
    1) With paper, we have effectively decoupled the entire mass of the mouthpiece from the horn. That is a bigger effect than any gap issue!
    2) Turbulence is a VERY controversial issue. The DC component when playing (expending our air) is a much different deal than the impedance of the trumpet at the various tones that we can play.

    The air in the trumpet is not moving fast enough to have turbulence be a real issue for the DC component in any case. If you are smoker, take a puff and then play until smoke comes out of the bell - 30 seconds to a minute is what I have measured.

    We can also measure the volume of our lungs and then play until we run out of air - knowing the aperature of the mouthpiece, we can calculate the maximum speed or volume going through. I will maintain that the main source of "resistance is our own lips. The more efficient that we play, the more our lips open and close like a valve, exciting the standing wave in the trumpet and requiring VERY LITTLE AIR pressure or velocity.

    Posts like this actually reinforce myths. There are specific functions of the gap that affect "blow" and "intonation", but not in the way described here. The differences here are better explained by the mass decoupling.

    Here is some real qualified research on the subject that maybe would shed a bit more light into the rest of what is happening here.....
    Mouthpiece forms - Institute of Music Acoustics (Wiener Klangstil)

    Intonation - Institute of Music Acoustics (Wiener Klangstil)

    This is the level and quality of research that is required to get to the truth. Until then, gap will continue to be controversial, subjectively working for some but not all.

    I am not questioning the issue of Gap. It is part of the trumpet equation. This demo proves nothing however and does not help explain what really happens.
     
  3. feedback@stomvi-usa

    [email protected] Piano User

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    Thanks for joining the discussion and I apologize if I was not clear in the purpose of this impromptu video/post: The purpose of this video was simply to help the trumpeter recognize some of the aspects that you, a clearly studied person on the subject, knows and has already experimented with. It was in no way meant to be a scientific treatise on the subject of the gap, or annulus.

    I have studied and there is a lot of information on our website (and in other posts we have participated in) regarding the science of the gap particularly as it relates to intonation (this is my main area of interest).

    You eloquently state that "The air in the trumpet is not moving fast enough to have turbulence be a real issue for the DC component in any case." Of course we agree and felt that this simple and non-scientific demonstration would help trumpet players understand this even though it may "feel" to them that the air is coursing through the horn. We also thought it might be fun for players to try.

    We also have done the "smoke" test and, depending on the register being played, have seen it take as much as 4-5 seconds for the smoke to make it from the mouth to the bell. In this amount of time the sound wave could have travelled about a mile.

    Again, thanks for taking time to join in and for the links which many will enjoy.

    K.O. Skinsnes, President
    Stomvi USA
     
  4. trickg

    trickg Utimate User

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    Robin, while you make some good points for your arguments, it's people like Bob Reeves, who have been working with the subject of the gap for decades who have effectively reinforced that the gap is a very important component in the mouthpiece/horn relationship. The above video might not be an idea example, but my experience doesn't track with your idea that decoupling the mouthpiece mass from the receiver is that big of a deal. For years I've adjusted the gap for my mouthpiece with clear packing tape, and it hasn't exactly been detrimental - it has been a positive adjustment, even if it pushes my mouthpiece gap maybe a bit too wide.
     
  5. gzent

    gzent Fortissimo User

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    Thanks for stating that. Gap is a very important part of the instruments and how it operates, but the OP provided little useful info.
     
  6. trickg

    trickg Utimate User

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    You know, I just noticed something here - Robin decided to try to take the president of Stomvi to task about a matter regarding gap, mouthpieces, trumpets, air speed etc. Interesting.

    One of the things that I think gets overlooked when thinking about the gap, air, blow and all of that, is that air speed is probably largely misunderstood within the trumpet playing community, and to that end, what I think I might know about it really isn't scientific, but here it goes anyway.

    When we think about the smoke test, it's obvious that air doesn't move quickly through the horn, so the gap may or may not have an effect on air speed turbulence, however, are we really talking about air speed, or are we talking about vibration amplitude, the maximum effect of that vibration, and how the gap affects that? It would seem to me that the latter is where the gap would have the biggest effect. To that end, I wonder what else could be looked at that might affect that relationship. Could the relative thickness of the wall of the leadpipe venture have an effect? What about the thickness of the wall of the end of the mouthpiece? What about the end of the mouthpiece itself? I've seen some mouthpieces that have almost a kind of ridged surface on the end of the mouthpiece. What if the end of the mouthpiece wasn't squared, but rather it was cut at an angle?

    Has anyone done studies regarding those things? If so, were they ever published?
     
  7. gzent

    gzent Fortissimo User

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    Absolutely those things factor in to how the system works. I've never seen anything published, but have heard Jason Harrelson
    speak about such things and how very minor changes in that part of the system (mouthpiece to receiver coupling) can make major
    changes in how the system works.
     
  8. Vulgano Brother

    Vulgano Brother Moderator Staff Member

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    An interesting chop building exercise is to buzz a tone on the mouthpiece (say, Bb) and slowly enter the receiver (while fingering that same pitch) while maintaining the same note. At a certain point the notes gets quite squirrely and the trick here is to fight to maintain that pitch until the mouthpiece gets seated. It is pretty good training for the concept that we control the trumpet.
     
  9. Sethoflagos

    Sethoflagos Utimate User

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    Think of the air moving 10 steps forward, 9 steps back. Although the nett air speed is relatively slow, the spot speed particularly at the nodes of the standing wave, can be much higher. So the fag smoke criteria is interesting, but really of no guide to the dynamics going on inside the instrument.

    One day one hopes that someone will publish pressure/airspeed amplitudes typically found within trumpet tubing, and some of us will be able to plug the data into CFD (computational flow dynamics) software and watch those little turbulent eddies spilling off the back face of the GAP and elsewhere (or not!). Until then, any conversation we have on this subject is just going to be smoke and mirrors IMHO.
     
  10. rowuk

    rowuk Moderator Staff Member

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    Actually there is not much controversy on gap among those that seriously and scientifically use it. The most important part of the concept is separating the DC (exhale) and AC component (the actual trumpet sound) in our view of what it does. The second issue is that we are not talking about horns like in loudspeaker horns so easily understood theory there does not apply here. Brass instruments are very long compared to audio horns, this makes the instruments "resonant". Gap is part of the equation in controlling that resonance it even applies when we use a piece of brass pipe with no leadpipe or bell. I prefer to think of it as controlled inefficiency at a section of the horn that interfaces the standing wave to our lips.

    In any case, one size does not fit all. Many years ago I had the pleasure of having Renold Schilke show us how his mouthpiece horn interface was optimal with NO GAP. The shank of the Schilke mouthpieces was knife sharp and designed to just touch the leadpipe leaving no "gap". I experienced a before/after gap adjust at the Monette factory - I can truly speak of big time changes in intonation and response (at least for a player at my level however strong or weak that may have been during my visit).

    One thing to consider: as there are aerosol particles in our breath (partially to completely digested food among other stuff), anywhere that there is "turbulence" in a trumpet, it would collect and be easy to find when cleaning. I have NEVER had verdigris in the the mouthpiece receiver in spite of it being the most "moist" place in the horn.

    As far as the pressure nodes due to the standing wave, they are transversal (push against the tubing).

    Cigarette smoke just shows the dynamics of the DC component. That part of the blow simply needs to be designed to let us breath at human intervals but still play long phrases.
     

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