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The Ressonant Frequency

Discussion in 'Luthier's Corner' started by YMB, Oct 5, 2009.


  1. YMB

    YMB

    Sep 22, 2009
    São Paulo - Brazil
    Dear Guys,

    I was very impressed with the quality of the replys I could read in the topic of Sustain Block.

    So I decide to open this thread just to you add substancial knowledge to this subject.

    A very complicated and dificult to understand subject : The Ressonant Frequency

    We could discuss about the Driver (Strings) Frequency, Physics of Energy Transfer, Wood Stiffness and its link with the Ressonant Frequency...

    Is a kind of Tesla work. Tesla did something with this, he found Earth Ressonant Frequency......and make a small Earth Quake.

    This is Crazy, and show us how important is this subject.

    Let's develop this subject. I have (zero) knowledge to share with you Guys, but I will love to hear from you.

    I'm very interested in Ressonant Frequency applied to the Bass construction...:bassist:
     
  2. ehque

    ehque

    Jan 8, 2006
    Singapore
    Sorry, but i don't think resonant frequency as a concept is useful to apply in bass construction...

    I'll tell you why though, resonance certainly has effects on the sound of a bass. It is partially responsible for feedback, deadspots, and the "liveliness" of the wood.

    However, its impossible for a luthier or even a physicist to design a bass to meet a specific resonant frequency, because of the very very complex maths involved, probably involving modelling, and the inconsistency of wood as a material, both across species, boards, and even different axis on the same boards.
     
  3. uethanian

    uethanian

    Mar 11, 2007
    the only way i could imagine this happening is if you made a single-piece resonating body out a uniform material.

    while it might be interesting to design, say, a drum with an exact resonant frequency, there's not much application for a string instrument unless you had only one string and all the stopped notes are from the overtone series of that one string...otherwise you'd get nasty discrepancies (for instance, a tempered major 3rd would clash with the harmonic major third of the resonant fundamental, and either sound dead or produce a wolf effect, i don't know which).
     
  4. Dead spot = resonant frequency found. Ideally the res. frequency of an electric bass is above or below any notes it can play, to avoid 'dead spots.'
     
  5. ehque

    ehque

    Jan 8, 2006
    Singapore
    Actually i'm willing to bet that a deadspot is a multiple of the resonant frequency, most likely half, or 3/2 times.

    A string vibrating at resonant frequency will dump some of its energy into the bass quite efficiently, but that's only half of the equation. The standard curve which you learn in physics 101 is a powered driver system, with the driven object a generalised energy sink (with damping factor only)

    A more accurate representation is with representing the string as an unpowered driver, but with fixed energy. As the string easily loses energy into the bass when vibrating near the bass' resonant frequency, the bass also easily gives energy back to the string when the driver frequency (the resonant frequency of the bass) is near the resonant frequency (the note the string is tuned to).

    If the resonant frequency is at such that the bass vibrating vibrates "out of phase" with the string - such as, it is tuned 3/2 times as high - the bass's energy, when sent back into the string, will cause even more energy loss, hence the deadspot.

    If the resonant frequency is at such that the bass vibrating vibrates "in phase" with the string - such as, it is tuned to the same note - the bass's energy, when sent back into the string, will cause the string to gain back some of its energy.
     
  6. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    Yes, if you add to that , one thing: the resonance must occur physically at the location of one of the two witness points of the string being fretted. Otherewise, the body or neck movement still has no effect on the string. See: http://www.acoustics.org/press/137th/fleischer.html (original paper, currently dead link)
     
  7. I'd believe that, make sense. I didn't take Physics. :meh:

    And I think it does, primarily at the nut. Hence the existence of devices such as the Fat Finger.
     
  8. ehque

    ehque

    Jan 8, 2006
    Singapore
    A well made, stiff bass, will most likely only have one resonant frequency, which will mainly be the neck vibrating back and forward.

    There's a study on how much a strat neck moves... i remember seeing an academic paper on it once, but that was a long time back. EDIT: Hrmmm, and there it is, posted above.
     
  9. YMB

    YMB

    Sep 22, 2009
    São Paulo - Brazil
    TNX Guys, now I'm printing this topic to study it....kkkkkkk

    Also I loved the ASA article, I really don't know how to applied this knowledge, but It's very important to every serious luthier know.

    This is research....and I love it
     
  10. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    Nope. The reason there's the common fender-bass-dead-D is that the antinode of a D note vibration occurs at the physical position of the first string, seventh fret.

    There are all kinds of vibrations, and they are not limited to bending. Torsion also plays a strong part, as evidenced both by the displacement plot in that paper, and by whatever evidence it was that Rick Turner says he saw.
     
  11. Interesting. I obviously have more reading to do.
     
  12. tdogg

    tdogg

    Jan 17, 2001
    Brooklyn Park, MN
    the resonant frequency of the forks in my silverware drawer is an A-flat. just thought id share. very obnoxious.
     
  13. mongo2

    mongo2

    Feb 17, 2008
    Da Shaw
    The little stained glass suncatcher we have in the kitchen window resonates on "C" and rattles like crazy against the window.

    It makes for a handy dandy quick and dirty tuning check. :)
     
  14. Beej

    Beej

    Feb 10, 2007
    Victoria, BC

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