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Inspired by this question on Music beta SE, I'm wondering if the human body has a strong resonant frequency. I guess the fact that it's largely a bag of jelly would add a lot of damping to the system, but is that enough to dampen it entirely?

What models for resonance might be used to model the human body? (E.g. weight-on-a-spring, with legs as springs?) What about individual, semi-independent body parts, like legs, or lung cavity (acoustic resonance?).

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  • $\begingroup$ what do you mean by that? $\endgroup$ Sep 26, 2013 at 17:46
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    $\begingroup$ @KaziarafatAhmed: What do you mean by "that"? $\endgroup$
    – naught101
    Sep 27, 2013 at 2:13

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There seem to be a lot of human body mechanical models, such as this one: enter image description here

As for applications, I have heard that sub-audio frequency vibrations have been considered as nonlethal weapons for riot control.

Addendum:
Guys, stop upvoting this. The image was not composed by me. I found it so long ago there's no chance to find the original source. Google reverse image search says it might be newbedev.com. In the "related images" section there are other similar interesting sketches on human resonant frequency.

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    $\begingroup$ That is a most awesome diagram. $\endgroup$
    – naught101
    Sep 21, 2012 at 12:12
  • $\begingroup$ @naught101, note however, that I do not quote the study, that produced those numbers :( $\endgroup$
    – Vorac
    Sep 21, 2012 at 12:54
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    $\begingroup$ I agree awesome diagram. It also confirms a story a friend of mine told about an engineer that worked for a company that makes huge shaker tables. Supposedly this engineer, working on top of the table lost his bowels when the frequency sweep passed through 7 Hz. That agrees with the 4-8 Hz abdominal mass natural frequency shown. $\endgroup$
    – docscience
    Oct 15, 2014 at 22:26
  • $\begingroup$ riot control? this must be related to brown noise $\endgroup$
    – image357
    Mar 18, 2015 at 20:21
  • $\begingroup$ I tried tracking down the origin of that diagram, but all clues end at powerstandards.com/HumanResonance.php. Note to self: books.google.ch/books?id=tYtfAQAAQBAJ&pg=PA30&lpg=PA30 sounds interesting... $\endgroup$ Aug 4, 2016 at 6:25
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I have just noticed the question. Indeed, the body does have very clear resonances. Nature has prioritised speed of movement over stability so limbs are underdamped and naturally resonant. It is likely that many rhythmic movements occur at the resonant frequency of the body parts involved (rather similar to the oscillation of some insect wings). A complication is that, like many biological tissues, muscles are very non linear and are actually much stiffer for small displacements than for large ones. This means that, for example, the resonant frequency of the human wrist is about 2 Hz for large oscillations but rises to ~ 10 Hz for small ones. There is some physiological literature on this subject - my late colleague and friend EG Walsh described some of it in his book, Muscles masses and Motion (1992, CUP). More recently I have been very interested in the contribution of resonance to the small, normally unnoticeable tremor that all humans have.

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This here is an experimental paper about the mechanical vibrations total resonance (i.e. the discrete frequency where it is found a human body as a whole resonates mostly):

Discussion of human resonant frequency

also found here.

"...found the human whole-body fundamental resonant frequency to be around 5 Hz. However, in recent years, an indirect method has been prosed which appears to increase the resonant frequency to approximately 10 Hz. To explain this discrepancy, experimental work was carried out in NTU. The study shows that the discrepancy lies in the vibration magnitude used in the tests. A definition of human natural frequency in terms of vibration magnitude is proposed."

The analysis of the experimental results of this paper lead to an important conclusion made by the authors that this resonant frequency is amplitude depended in some extend thus it can vary depending the amplitude of the mechanical vibrations.

"...that the higher the vibration magnitude, the lower the detected human resonant frequency. Therefore, the definition of the human resonant frequency should refer to the vibration magnitude. This paper suggests that, for practical purpose where the vibration magnitude is higher than 0.1 ms-2 (such as in the study of earthquake and traffic), the human resonant frequency could be assumed in the range of 3 to 7 Hz."

Also another conclusion the authors of this paper making is that most of the vibrations can be dumped by the human depending also by muscle-tension:

"...There is slight difference between various postures. If we refer to the muscle tension, it can be suspected that tensed postures can damp the vibration more effectively than the relaxed ones"

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