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I've come across some posts that mention "Young's modulus" in relation to guitar.

Young's modulus is discussed on physics.SE (Young's Modulus and Vibrating String Harmonics), but I'm looking for a less technical explanation.

On this site, it's mentioned in a few posts in relation to guitar:

  • This answer to "What types of plastic and manufacturing techniques are used to make guitar picks?"
  • This answer to "vibrato on classical guitar is more of a “side to side” motion?"
  • This answer to "How does string gauge affect intonation?"
  • This answer to "Bridge intonation patterns on stringed instruments"
  • And this answer, also to "Bridge intonation patterns on stringed instruments"

In lay terms, what is Young's modulus, how does it relate to guitar, and does it similarly relate to other stringed instruments?

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  • This question is answered in the last two paragraphs of music.stackexchange.com/questions/114451/… – Aaron May 15 at 16:19
  • The last sentence is important - it may well relate to fretless instruments, the players of which maybe don't even realise they compensate without even considering moduli! – Tim May 15 at 16:35
  • The last sentence has some importance. It may have relevance to fretless instruments, the players thereof not even realising that they compensate for moduli while in mid-flow! We await, with bated breath, the findings of Jemenake! – Tim May 15 at 16:39
  • It describes if you need a lot or a little force on the area(stress) to make stuff bend like rubberband(strain). – Emil May 15 at 17:04
  • Well, it's an inherent property of all solid materials. So it does apply to fretless instruments too, but be prepared to do some interesting integrals if you want to actually calculate something with it. – ojs May 15 at 18:04
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Young's modulus is a parameter of given material describing relation between force and deformation.

The formula is E = σ/ε, where E is Young's modulus, σ = F/A is the tensile stress, or force F over the cross-sectional area A (e.g. string cross-section), and ε = (l - L0)/L0 is relative change of length. The units of E are Pa (pascals); one could visualize it as pressure occurring in the material in response to deformation. https://en.wikipedia.org/wiki/Young%27s_modulus https://en.wikipedia.org/wiki/Stress_(mechanics) https://en.wikipedia.org/wiki/Deformation_(physics)

Young's modulus of the string material is one of the parameters determining how strings are susceptible to intentional or unintentional bending, and how the pitch may vary due to string elongation due to vibration. E.g. listen to pitch change of long notes played on steel strings in the intro to this song:

Young's modulus also determines the relative longitudinal and transverse force exerted by the string on the bridge due to vibrations [Fletcher, Rossing, The Physics of Musical Instruments]. I presume this affects differences between classical (Nylon strings, Young's modulus of 2–4 GPa) and acoustic (steel strings, Young's modulus ~40 times larger) guitars, I however can't provide any details.

Young's modulus is an important parameter, but not the only one to consider. E.g. Nylon strings have much lower value than steel strings, but they have also lower yield and ultimate strength (45, 70 MPa) in comparison to e.g. piano wire (2000–3000 MPa https://en.wikipedia.org/wiki/Yield_(engineering)). As a result Nylon strings are typically made thicker and are tuned at lower tension (so they don't break), which counteracts some of the effect of large difference in Young's modulus. Thicker nylon strings also absorb energy of higher harmonics, resulting in more mellow sound.

Young's modulus determines speed of sound in the material. E.g. for an elongated rod (like a string) it is c² = E/ρ where c is the speed of sound and ρ is the density. (https://en.wikipedia.org/wiki/Speed_of_sound#One-dimensional_solids) I presume this must be an important factor when choosing materials to make an instrument, especially larger parts with resonances significant for the instrument sound.

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