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Thread: Tuner for tap tuning

  1. #51
    Adrian Minarovic
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    Default Re: Tuner for tap tuning

    BTW, here is where serious researchers among violin makers were some 10 years ago...

    https://www.reghviolins.com/publicat...pp.187-230.pdf
    Adrian

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  3. #52
    Registered User j. condino's Avatar
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    Default Re: Tuner for tap tuning

    Excellent link Adrian.

    As a former student of the Oberlin Acoustics workshop, I've been telling people for almost 10 years that this is the place to go, but the only response I ever get is a blank stare while maybe getting asked what tuner to buy....

    I've brought my personal wood and instruments for serious analysis & number crunching, working on them and manipulating the build process while in the lab. There are some other serious players in the mandolin world who have attended multiple times. Scaling things up, the Oberlin double bass workshop is the best one in the country.
    www.condino.com

    Crafted by hand in a workshop powered by the sun.

  4. #53

    Default Re: Tuner for tap tuning

    The whole study of modes of vibration is pretty well established in the engineering world. The basic text on the subject is Engineering Vibrations written by J.P. den Hartog in 1957. The study in the field was jump started by the famous collapse of the Tacoma Narrows Bridge in 1940. Vibrations are routinely modeled using finite element analysis. This is done for earthquake studies, particularly in things like nuclear plants, dams and skyscrapers where the consequences of an unexpected resonance can be catastrophic. There are known sets of forcing spectra, vibration functions from historical earthquakes, that are input into three dimensional models to look for unexpected resonances which may drive collapse. Machinery and heavy equipment is similarly studied for forced resonances that may damage or break things. I have personally witnessed shaker table tests at John Deere and Caterpillar where entire front end wheel loaders and road graders are put on a big shaker table and shaken up to look for resonances that may cause damage.

    Some people, particularly at the University of New South Wales have done finite element studies on guitars. I started to look at it for mandolins when I was still working and had access to the software but did not get too far before retirement. It requires quite a bit of computer horsepower and there are limits on what you can model due to this. Flat topped instruments with their uniform thickness are more straightforward to model mathematically.

    There are two sets of significant numbers, the frequency of the modes and what is called the modal participation factor. The participation factor measures the percentage each mode contributes to the total energy of the system. With these two sets of numbers you can start to define how the system behaves. The fact that the pretty pictures of the mode shapes do not change much in the laser interferometry experiments tells us some things but the actual numbers for the modal frequencies and participation factors have a lot more bearing on how the system behaves. The mode shapes can be pretty similar but if the participation factor goes way up or the modal frequency changes for a particular mode with a change in stiffness or mass distribution on the structure that can make the difference between a structure or machine that survives or is shaken apart.

    The bearing this has on musical instruments is that only a limited amount of work has been done to determine these numbers. How a system behaves when driven by a forcing function, whether an earthquake or a plucked string, can be quite a bit different from a free vibration when tapped. We cannot really define what is a "good" tone and know the actual frequencies of the main modes let alone the participation factors. Peter Coombe's work and the Oberlin work is a good start but the Chladni patterns and interferometry mostly give mode shapes and frequencies and tell a lot less about the relative strength of each mode. After the first four or six modes the contribution is probably not high but we do not really know even that for certain. The FFT analysis can also tell some information about these things if you have you have the right input and understanding.

    Till you know the numbers for the modal frequency and participation factor for several of the primary modes under several different forcing frequencies of the different string and fret positions you have not really understood how the system behaves. For the forseeable future building guitars and fiddles, let alone mandolins will remain more art than science.

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  6. #54
    Registered User sunburst's Avatar
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    Default Re: Tuner for tap tuning

    Quote Originally Posted by CarlM View Post
    ...For the forseeable future building guitars and fiddles, let alone mandolins will remain more art than science.
    I was right there with ya unlit that last sentence. If it had been "more craft than science" I would have been with ya all the way through.

    I admit that I don't have a very thorough understanding of the science of vibration and the science of musical instrument function, but simply knowing that instrument parts must obey the lows of physics, that plate modes and air modes exist and are what we have to work with is enough to steer me in directions that might just be productive.
    Realizing that more-or-less randomly selected frequencies for "tap tones" are not magical, that "tone bars" do not "distribute vibrations", that sound waves don't "bounce around" inside of instruments, that surface texture doesn't behave the same way inside of an instrument and inside of a concert hall, etc., etc. saves me from wasting time following those misguided paths. A basic understanding of the science of musical instruments is enough to steer me toward things that might matter as opposed to things purported by folks; things that I can see are not supported by the scientific evidence that we do have.

    Will we ever have full scientific knowledge of how a mandolin works? Probably not, and even if we do, how much good would it do? Instruments have been reverse engineered for centuries, especially in the case of violins. Is there room for improvement? Maybe, but the sound of a violin is established, the shape and size of a violin are established, change things very much and we no longer have a violin.

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