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I am trying to figure out if it would be possible to change the resonant natural frequency of a solid-body guitar. For example, let's say it resonates at 100 Hz and I want it to resonate at 200 Hz. Is there an existing electronic device(s) that could be used to somehow change the resonant natural frequency? What about adding different density metals into the body? I am just brainstorming possibilities.

Michael Seifert
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Curt Thiel
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    Not everything has a resonance. Do you have some reason to think that an electric guitar does? Eg, this pdf, quoting Halliday et al, says electric guitars don't, which seems reasonable to me. But when something has a resonance, changing almost any aspect of it will change its resonant frequency. Please, though, for the future, try to limit your questions to real questions, and not "brainstorming", which isn't the purpose of SE.Physics. – tom10 May 18 '22 at 16:11
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    @tom10, The paper that you cited appears to refute Halliday et al. It says that a solid body does resonate. And that makes sense. Practically any solid wooden artifact will resonate a little bit if you strike it. But I'm pretty sure that electric guitar makers usually will strive to make all of the vibration modes of the body and neck highly damped. (I.e., they want it to give a dull "thump" when you strike it. They don't want it to ring like the bars of a marimba.) – Solomon Slow May 18 '22 at 16:25
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    @tom10, I disagree with your suggestion. The OP has a real question, brainstorming is a process that one could use to get new questions. – nicoguaro May 18 '22 at 16:27
  • Yes Tom they do. Ask a Luthier or Musician or the Physics Dept at Illinois https://courses.physics.illinois.edu/phys406/sp2017/NSF_REU_Reports/2002_reu/Eric_Moon_REU_Report.pdf Also, here is a research article with a lot more recent citations which casts doubt on the pdf you shared. https://www.researchgate.net/publication/52001722_Wood_for_sound

    I am not a developer myself but own a software development company. https://d3vsource.com

    This is a real question. I have a problem I am solving. Sorry if I improperly posted it. Thx.

     – Curt Thiel May 18 '22 at 16:41
  • Many musicians have their favorite Guitar. Most will say it is special because it resonates a particular way -different than others of the same model. Part of it is because of Youngs Modulus and how it determines the acoustical properties of different wood types. I want to change how a guitar resonates if possible so it can be adjusted. – Curt Thiel May 18 '22 at 16:48

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Yes, the resonant frequency of a solid guitar body can be changed by adding or removing material but it provides no benefit to the sound that can't be accomplished by less destructive means such as the choice and placement of guitar pickups, choice of amplifier, etc. For the purposes of sustaining notes, a guitar that resonates equally for every fretted note is ideal. I know of no solid body design that accomplishes that but electric guitar strings are slightly magnetic, so resonant frequencies on individual guitar strings can be enhanced by changing the distance between the string and the surface of the pickups.

Stevan V. Saban
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Solid-body electric guitar does indeed have resonant frequencies. They work through a transduction process generating an electric signal that is later radiated to the air using a loudspeaker. This is different from a classical guitar where the radiation process happens through the top plate. There, the first two vibration modes are really important for the mechanical behavior of the guitar (see this answer for more details). So, it is probable that you don't want to change the resonant frequency of a solid-body electric guitar since it does not play a role that is that fundamental in its behavior.

After mentioning that, let's consider a single-degree-of-freedom vibrator. The resonant frequency is given by

$$f = \frac{1}{2\pi}\sqrt{\frac{k}{m}}\, ,$$

where $k$ is the stiffness and $m$ is the mass. So, you need to increase the stiffness-to-mass ratio. You could carve some holes, for example, making it something like a foam.

nicoguaro
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  • Great info, thx Nico! – Curt Thiel May 18 '22 at 16:49
  • @CurtThiel, you can upvote and accept answers. – nicoguaro May 18 '22 at 16:51
  • Apparently I do not have enough points yet to vote :( – Curt Thiel May 18 '22 at 16:55
  • Do you think it is possible to use a Haptic Actuator (which can vibrate between 10hz - 500hz) to change the resonant frequency of the guitar? – Curt Thiel May 18 '22 at 17:35
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    @CurtThiel, I think that you are confused with the meaning of resonant frequency. A resonant frequency is a characteristic of the system, you are suggesting adding an external source... that would not change the system, only the frequency of excitation. – nicoguaro May 18 '22 at 19:41
  • Yes, I could be :) But if an object is vibrating at a particular frequency in its natural state and you imbed a device internally which can vibrate at different frequencies, would that not change the natural frequency of the object by artificial means? – Curt Thiel May 18 '22 at 19:48
  • No, it does not. If the material is "active" you could change the material properties changing an external parameter, but that's it. – nicoguaro May 18 '22 at 19:49