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David Beard

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Posts posted by David Beard

  1. 2 hours ago, Andreas Preuss said:

    One might ponder if Cremonese violin makers didn’t try to get as close as possible to a ‘membrane like violin top’.

    Just change your word to diaphragm, skip the issue of implied stretching.

    In a membrane or a string, it's implied that the restoring force comes of an elastically stretched material.

    In a rod or diaphragm, the restoring force comes from the elastic stiffness of the material.

     

     

     

     

  2. 3 hours ago, Andreas Preuss said:

    capacitance? Like in an electric circuit?

    Would it be as easy as 

    Capacitance is a function governed by the entire mass?

    And how would a violin with low capacitance sound versus a violin with high capacitance?

    ---------------------

    Don't know if this is related to this. I watched the video where Ray Chen plays a 65 dollar fiddle and compares it to a 10 million dollar Strad.

    At one point he says that the cheap violin feels for him like 'It wants to continue to vibrate on the same note when I am already on the next'. 

    Wouldn't this be a description of high capacitance? 

    No. That's a description of high Q and low dampening.

    Think of changing fingers right after plugging a string.  Guitarists do this a lot deliberately. Violinists don't normal do this, but I'm we can all remember moments goofing around.

    The energy persists, but changes to the new signal.  Capacitance lends a persistence of energy, not necessarily of signal.

    It is high Q resonances that want to keep energy at their pitch, instead of responding to a driving signal.  

     

  3. 18 minutes ago, uncle duke said:

    Is ot possible the energy simply permeates through the wood and varnish to the outside surface.  Things seem to be better after the violin has warmed up to at least the human body temperature.

    Side note - long ago, I was told that air can actually go through concrete - that gave me the thought for the above comment.

    1) as heat, or 2) as vibration leaving the instrument as sound.

  4. 4 hours ago, Andreas Preuss said:

    But it is using energy where it DOES NOT produce sound even if it is not lost. If energy loss equals only friction, I don't know what it is all about anyway. Too complicated with no benefits.

    Anyway, those abstract calculations tell me only that if I can alter the assumed 4 percent to 5 I have an increase of 25% which is a lot.

    I remember quite well, when my father, a physicist, bought the book read it page by page. When I looked into it I saw only those Einsteinian formulas and thought 'Forget it!' A little later my dad was scribbling with pencil things in the book and when I asked him what he is doing he got into a small rant what Cremer is all wrong about. 

    I rather spend my free time to sharpen chisels for my next experiment and maybe I have a good idea...

     

    An active vibration or standing wave isn't 'using up' that energy.  Think of it as storing the energy.

    From the storage in a resonance, the energy can: 1) linger, 2) go back to the instrument or another resonance, 3) radiate as sound, 4) plastically deform something, or 5) dissipate as heat.

    Only the last three of those actually lose energy from the system.

  5. temperature v heat

    volts v current

    water speed v flow

    *******

    Sound is a transfer of energy as vibrations.    Like the energy transfers above, there is also an aspect of the 'heft' of what is happening.

    With heat, we talk of temperature, but also thermal mass.

    With vibrations, there is a similar aspect, though we don't seem to have ready language to address it.

    The energy in vibration is not just about the amplitude of the vibration, but also about the mass that is in motion.  More mass moved at the same speed/amplitude holds greater energy.

    Yes, thin light plates will swing more for equal energy.  But heavier plates brought into equal motion will hold more energy.  And will have more capacity to radiate energy.

     

  6. 1 hour ago, Andreas Preuss said:

    What about the vibrating neck which doesn't produce sound?

    I wonder too how this compares to other music instruments. Maybe there is, for what reason ever, always a big energy loss factor.

     

     

    Vibration itself isn't loss.  It's dampening in to heat that is loss, and radiation of as sound also.

    Most vibrations, like the neck, will  cycling through the instrument until dissipated as either sound/noise radition or heat. I can't think of any other dissipations for a violin.

  7. 21 minutes ago, Anders Buen said:

    I think Cremer tried to estimate this. If I recall correctly is was about 4%. I may look that up tomorrow. The number is correct. He say only 0,4% per cycle is radiated as sound. Thank God, our ears are very sensitive.

    That seems very low.  Much lower than I imagined.

    I guess there are several points where it would be interesting to know power levels.

    There is the arm waving to move the bow. That has a power level.

    There is the transfer of enegry from the bow contact into string vibrations.  That has a power level.

    Then there is the energy transfer from bridge feet into the violin.

    And at a later pointed there is the energy radiating as sound.

    If the overall drop is 96%, most of the loss must be at the bow arm to string transfer.

    There can't be too much energy lost later, as there aren't any heat issues with violin playing.

  8. 24 minutes ago, ctanzio said:

    If you add the fundamental and the overtones together for a vibrating string, you get what looks like a single kink traveling up and down the string. IOW, the vibration of the string is not symmetrical as one might expect for a perfect sine wave. 

    Although it is common to refer to the shape of the wave as "sawtooth", it is actually pretty far off from that shape. A perfect sawtooth would only generate odd numbered overtones. Because of the complex shape of the kink, it is the sum of all the overtones, not just the odd ones.

    Your description of how the bow is actuating the string is correct. It constantly tugs the string to one side, and the kink traveling up and down the string periodically increases the force against the motion of the string to kick it loose until it slows down enough for the string to grab it again. It is during the kick loose and sliding phase where I would expect noise, or small vibrations, to be introduced into the string.

     

    Yes. As ctanzio says, vibrations add.

    The OP asks how harmonics/overtones are reproduced in a violin.

    One thing that doesn't happen is they don't travel as separated sine waves.    Instead, vibrations add together and travel with the shape of their summed totals.

    This means that when we hear a sound, we aren't very good at distinguishing between a sound composited from many separate sources versus a single source that produces total of that composite in one complicated wave shape.

    This is why we aren't great at distinguishing a speaker reproduction from an orchestra of seperate sound sources.

    We can separate harmonics mathematically, but in a medium they are combined.  

    We can also isolate and stimulate separate harmonics on a string, as we all know.

    For these reasons, it's easy to make the mistake of talking and thinking about overtone harmonics as if they somehow did exist as independent sine wave shapes in a string or an instrument.

    But mostly they are more just mathematical artifacts of a non-sinewave wave shape.  They are the simple sine waves that add up to the shape of the actual physical wave present.

    When we strongly pull a string to the side in a triangle shape and then let go, the distortions shooting back and forth along the string have shape related to the initial triangle shape we pulled.  Nothing much looks like sine waves.

    But when we hear that, our ears and brain process the cyclic shape of the presure distortions reaching us as a sum of sine waves.  So we hear harmonics.

  9. 10 hours ago, Peter K-G said:

    That's kind of what I was thinking, when I starting the question, followed with some tests.

    I also thought that the notes/string motion by themself could contribute, but it does that only when a note is very near a mode.

     

    Yes.  The bow can pull the string only when it's velocity and the strings are similar.  

    That will tended to be cyclic, but won't be strickly so.  

  10. 1 minute ago, jezzupe said:

    D. Burgess wrote "a regular pattern  corresponding with the frequency of the played note"

    So that means it's matching the frequency cycle of what ever note is being played? and therefore will change note to note? 

    That is the tendency. But reality includes transitions and imperfections and complications.

    Even that the most skilled players include 'consonances' in their playing. It isn't all vowels.

    Just plain not as simplistic as described.

  11. 9 minutes ago, jezzupe said:

    How is this possible do you think?, I'm not disagreeing, just wondering how something with such little mass {the string} could "send" energy transfer back to the bow, {way more mass} and start to drive the bow hair? or dictate a patterned skipping or skating, is it that the bow hairs act as individuals in such a dynamic state? 

    No. It is the cycle of stick slip that tends to fall into pattern.

    But, noise are still in the sound.  And virtually the energy comes via the bow.

    And any noise in the system, of whatever origin, is energy that has the potential to be captured into the signal.

     

  12. 16 minutes ago, Anders Buen said:

    There may be a randomish behavior at the startup, as David B writes, then the behavior becomes periodic and phase locked. There is no randomness to that basic bowed string sound from a trained player.

    i think part of the noise comes from the slip phase, but I an not sure. The noise may be randomish in some way.

    The noise comes from the imperfection of the phase lock you describe.  And yes, it greatly depends on the player.  

    But what you describe is a state that emerges. It is not 100% of the action.

    And, unless there is plucking or banging, 100% of the energy, including all noise, is originating with the bow action.

    Bows also partial skate.  And don't forget, scrunch and other noise are deliberate parts of player bow articulations.

  13. 1 hour ago, David Burgess said:

    I will disagree. Initially, the source energy can be thought of as noise, but after even one round trip of the traveling string kink between the bridge and upper nut (or finger), a pattern starts to be established, which kicks the bow hair loose from the string in a regular pattern  corresponding with the frequency of the played note

    Yes. Where is the disagreement?  Unless you are claiming that the dynamic you describe is 100%.  On that we would disagree.  

  14. 1 hour ago, Marty Kasprzyk said:

    I'm quite sure the noise between a note's harmonics are produced by the bow hair. Attached is a plot up to 8000Hz of a bowed violin open G string as a blue line.  Also plotted is an orange line showing the bowing of the violin bridge upper bass side edge which produces a "hissy" kind of white noise.  

    The violin body/bridge filters the bow noise just like it filters the string harmonics of a note and the orange line of the bowed bridge edge follows the same envelope shape as the noise of the bowed note.

    Also attached is the same plot going up to only 600Hz.  The A0 resonance peak (~280Hz) shows up as noise just like Peter had found.  All violins probably do the same thing.

     

    Screen Shot 2021-05-27 at 1.42.40 PM.png

    Screen Shot 2021-05-27 at 1.41.28 PM.png

    As you say, the strings, the instrument, the whole system is fundamentally an energy transducer.

    The primary (basically only) energy input is the essentially random stream of pull/slips from the bow action.

    This source energy can be thought of as noise, an essentially random stream of energy kicks -- white noise.

    Some of this white noise source energy will pass through the whole transducer and radiate as still simple white noise.

    The big question for all stages of the instrument is 'how much of the white source energy falls into musical signal and how?'

    A good part of the energy falls into signal initially at the strings. The quality of the strings and the player's action matter greatly at this stage.  And then, a portion of this signal energy will pass into the instrument through the bridge which will act as a filter.

    But also, a portion of the white noise energy will pass into instrument still as white noise.  The question we don't ask enough is how well does the instrument keep capturing that noise energy into the signal?

     

  15. 4 hours ago, Rue said:

    Consumers can/will still get bargains, consumers are good at ferreting out deals.  That's the joy of the hunt.

    It wouldn't take long for consumers to get used to a 'new normal' in the violin market. 

    The only unhappy group would be the 'crooks' (is there a more polite word I should be using?).

    Networking is important!

    This is the root problem.  The only way to reliably get that treasure hunt buzz is to prefer self-delusion over clear eyed truth.

    For the average buyer to go to competent and honest dealer believing they will see what the dealer missed is delusion.

    To go to the rumage sale believing they will spot the treasure amidst the trash is again delusion.

    To go to a scammer unscrupulous buy (ebay?) believing the shark won't bite them is again delusion.

     

    But, if they find an honest dealer who pulls away the delusions and offers an honest and transparent deal, they won't be happy.  Many will walk away a seek out a pleasing delusion.

     

    That is the problem.  It real isn't about the dealers, honest or otherwise.

     

  16. I think stringing and tuning the strings matter greatly.

     

    * The 'membrane' or soundboard response should happen as long the materials aren't too thick and stiff.

    * Some of resonance responses depend on enough mass being present.  Mostly I'm thinking of the extra back mass.  If that is significant enough it can contribute response to some playing imputs that are other wise unavailable.    

    * Coupling of respnses also matter.  The more heavy and stiff the overall building, I think it can interfere with things like the body and air responses coupling up and influencing each other.

    I believe there's a famous rock and roll guitar maker that says something like 'a good playing instrument is just on the verge of falling apart'.  I think this largely has to do enabling responses to couple readily.

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