Shock Waves Propagating from bell of trumpet

Discussion in 'Trumpet Discussion' started by gordonfurr1, Feb 13, 2015.

  1. gordonfurr1

    gordonfurr1 Forte User

    2,107
    1,091
    Aug 2, 2010
    North Carolina
    Thanks to the referenced source (Acoustical Society of America, Volume 114, No.6, Pt.1, Dec. 2003) we can visually discern the acoustic wave/shock wave effects at a few frequency/volume levels. It is interesting to me especially to see the TURBULENCE roiling out the bell of the trumpet at the given notes...One might expect the wavefronts would propagate cleanly from a trumpet, but that is apparently not entirely the case as shown here. I remember TM member Sethoflagos mentioning the dispersion of the internal wavefronts in a system by the radii differences in bends, and that made sense to me. What I wonder is...what can be done about it...save reverting to herald trumpets (and even then). I wonder if some sort of twisting or convolution on the inner arc of a bend might help contribute to the waveform remaining dense, but then that in itself would add monstrous complexity.
    Hmmm.
    Anyway, I found these images very interesting. The pitch and volume are indicated in the title under each photo.

    WAVE FRONTS AT FRONT OF TRUMPET Photos by gordonfurr1 | Photobucket
     
  2. rowuk

    rowuk Moderator Staff Member

    Age:
    61
    16,616
    7,957
    Jun 18, 2006
    Germany
    Gordon,

    we have a couple of things happening here. Of course not all frequencies "see" all parts of the bell. Monette on their bigger horns has a bigger bell, but the last ½ inch is squared off and does not follow the horn taper. This dramatically changes the way that lower frequencies are launchedbut keeps the bell acoustically smaller at higher frequencies which makes it easier to play up there.

    Remember that what we hear in front of the trumpet is "leakage" of the standing wave due to "not" religiously following horn theory to maximize efficiency. Here is another link that could up your geekiness:

    http://iwk.mdw.ac.at/lit_db_iwk/download.php?id=15929

    and more than you would ever probably need:
    Effect of wall vibrations - Institute of Music Acoustics (Wiener Klangstil)
     
    J. Jericho likes this.
  3. FireandAir

    FireandAir Pianissimo User

    106
    52
    Aug 12, 2014
    Would we WANT to do anything about it? I imagine the whole nature of the wave propagating through air (which is of course unstable) is what gives the sound its color and richness. That's what sound IS, really. Happens to singers as well, I'd guess.
     
  4. gordonfurr1

    gordonfurr1 Forte User

    2,107
    1,091
    Aug 2, 2010
    North Carolina
    Yes, thank you. I like your term "leakage" of the standing wave...I am still digesting that notion, it seemed sort of counter-intuitive to the lay mind that MOST of the sound energy reverts backwards at the bell (or just beyond) as we discussed a week or so ago...I was well aware of reversion effects existing, just didn't expect that almost ALL the energy reverts...And after Sethoflagos shared his information about the effects of the radii differential on the wave fronts it had me cogitating. So, I did a little Googling for documentation of the effect and came across this article (which wasn't really exactly what I was seeking but thought it interesting). My big take away from this article was how roiling/convoluted the sound energy pouring out appeared. With the "clarion" nature of a trumpet being a big calling card, I would have naturally supposed the output would be more...refined...instead of so chaotic. Surely the image of the FORTE HIGH G looked a little surprising. Not so much the bow-shaped shock wave (I would EXPECT that from a trumpet) but the ROILING..directly in front of the bell. I would have expected a bit more ORDER there for the seeming clarity of the sound. It looks more like the pattern in a coffee cup a few seconds after pouring in the hot java and patterns have started to decay.

    If the effects of the bows are "confusing" the pressure waves as Sethoflagos mentioned, what COULD a trumpet be made to sound like if those effects were refined out?
    It is simply a natural curiosity to wonder about this.
     
  5. gmonady

    gmonady Utimate User

    18,127
    9,302
    Jan 28, 2011
    Dayton, Ohio
    Nothing gives me greater pleasure than seeing a singer propagate through air.
     
  6. gordonfurr1

    gordonfurr1 Forte User

    2,107
    1,091
    Aug 2, 2010
    North Carolina
    "Would we WANT to do something about it"...dunno. Maybe. Probably not, but maybe. Folks are tinkering and thinking all the time about small changes and effects to our instruments...and sometimes BIG changes also. Tinkering will never stop, nor should we want it to stop. My interest in this is not only trumpet, but I am working on a permutation of another instrument that uses a similar acoustic process...so, I need to continue digging and thinking about these things.

    Further, the efficiency of the trumpet is important in regards to playing effort. I've seen lots of posts encouraging playing with less "pressure", part of the effort is expended in achieving a particular volume/tone mixture with a given efficiency of acoustic system. If the desired volume/tone were able to be achieved with less pressure at the mouthpiece, there could be benefit. Inefficiencies absorb some (or a lot) of our energy. The "trumpet world" rotates around more than just performance artists...though they are nearest the center. There are all sorts of folks trying all sorts of new things to enhance the equipment an artist has at his disposal...engineers, medicalists, metallurgists, designers, and...imagineers.

    Who breaks the paradigms?

    Usually, those nutty imagineers walking past who don't know better than to throw out a question.
     
  7. gordonfurr1

    gordonfurr1 Forte User

    2,107
    1,091
    Aug 2, 2010
    North Carolina
    I have the occasional "propagating through air" dream for myself.
     
  8. Solar Bell

    Solar Bell Moderator Staff Member

    8,188
    1,912
    May 11, 2005
    Metro Detroit
    I'm just going to play my trumpet.
     
  9. gordonfurr1

    gordonfurr1 Forte User

    2,107
    1,091
    Aug 2, 2010
    North Carolina
    And we know what your exhaust looks like. :D
     
  10. Sethoflagos

    Sethoflagos Utimate User

    5,332
    4,732
    Aug 7, 2013
    Lagos, Nigeria
    It could sound like a flute.

    On a well designed trumpet, the 'confusion' caused by the bows, if equal in lead and lag characteristics, would cancel itself out due to destructive interference. I'm reluctant to use the term 'amplification' but the trumpet 'conserves' those waveforms that correspond to the resonant frequencies of the instrument and are in phase with the excitation. These are reinforced by constructive interference, whereas the rest are damped by destructive interference.
     

Share This Page