Violin strings are either single core materials or of the wound variety with a single core of one material wound with a helix of another (usually heavier) material to give the string a lower resonant frequency. In analyzing the acoustic impedance of a wound string, which part will determine the acoustic impedance of the string , the core or the outside helix material? Or will the overall impedance be somewhere in between the two?

  • $\begingroup$ I'm not an expert in acoustics but isn't the acoustic impedance a function of the resonating space (and medium) not the properties of the vibrating strings themselves? Much the same way that electrical impedance is a property of an electrical circuit not the current generating method. $\endgroup$
    – atom44
    Mar 15 '16 at 11:27

I'm not sure you understand what "acoustic impedance" is. The string by itself has a resonant frequency defined by its elastic modulus, the applied longitudinal tension, and length. If you really want to know how well it couples to the air around it, I suspect you'll be diving into an ugly bit of math. For one thing, unlike a speaker cone or a trumpet (for two examples), the string is coupled to the air along its full length, and primarily in two directions (the plane of vibration).

  • $\begingroup$ Hi Carl, acoustic impedance is an intrinsic property of all materials, like thermal or electrical conductivity. I don't know why you mentioning "coupling to the air around it", that has nothing to do with my question. Does air coupling have anything to do with measuring say the resistance of a piece of wire in ohms ? $\endgroup$ Mar 15 '16 at 21:52
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    $\begingroup$ @WilliamHird Sure, acoustic impedance = density x acoustic velocity. But the vibrational motion of a violin string is a bulk motion of the whole string, not the small perturbation of a stress wave propagating at the acoustic velocity. The vibration frequency is a function of the state of stress in the string (i.e. tension) which is not an intrinsic property of the string materal - it is simply a geometrical property = force / area. I'm at a loss to see how using acoustic impedance in this context is going to help in understanding the physics of a violin. $\endgroup$
    – alephzero
    Mar 16 '16 at 1:58
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    $\begingroup$ That's easy alephzero, my question doesn't have anything to do with the physics of the violin. $\endgroup$ Mar 16 '16 at 5:16
  • $\begingroup$ @WilliamHird If that's so, then you might get better responses if you clarify in the problem statement why it is that you're trying to analyze the acoustic impedance of a wound string. For example, are you actually interested in violins, or is the violin string only an analogy (if so, what for)? The manner in which the acoustic signal in the string (or analogue) is generated may also be relevant. $\endgroup$
    – Air
    Mar 16 '16 at 19:42
  • $\begingroup$ Hi Air, I intentionally avoided any mention of the violin body / instrument so as not to confuse anyone, it is purely a question of string dynamics. I could have worded the question "guitar string or banjo string", its about the string, not the instrument.People are reading too much into the question, sorry if I bruised any egos here. $\endgroup$ Mar 16 '16 at 21:40

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