Are jaw noises infrasound?

  1. A while back I read a meterology text book to learn about the atmosphere and on one of the pages there was a factoid about the human jaw resonating at an infrasonic frequency between .4-.8 mhz. I think it can be heard when you clench your jaw and release it. I believe this is relevant because most of information about infrasound I find talks about how it can cause anxiety and other phsyiological changes in the body, but finding the information about the jaw is difficult. Links would be awesome. I recieved an infraction from an admin. because I asked a question about this factoid and would like to know if it can be verified.
     
  2. jcsd
  3. mfb

    Staff: Mentor

    Re: Search for... something

    .4-.8mHz? This corresponds to a period of 20 to 40 minutes. I don't think there is any mechanical system in the body resonating at such a low frequency. In addition, "sound" with that period would be considered as atmospheric pressure variations and not as sound.
     
  4. Evo

    Staff: Mentor

    Re: Search for... something

    Your infraction was reversed, and your original post was nothing like this.

    These sounds, clicks, pops, etc... are clearly audible. Infrasound is under 20 Hz, you showed mHz, that wouldn't be right.

    http://adsabs.harvard.edu/abs/2001SPIE.4317..469B

    Usually any sound emmited below 20 hz can't be heard by the human ear.

    http://en.wikipedia.org/wiki/Temporomandibular_joint_disorder

    http://en.wikipedia.org/wiki/Infrasound
     
    Last edited: Jan 4, 2013
  5. If you're talking about 4-8Hz, that would make sense. I wrote a small section in my recent dissertation regarding the adverse health effect of environmental noise, including low frequency noise and infrasound. A lot of the adverse effect are attributed sleep fragmentation which has been shown to affect a number of human processes including waking psychomotor performance (van Dongen et al, 2003); memory consolidation (Stickgold, 2005); creativity (Wagner, et al 2004.); risk-taking behaviour (Mckenna et al 2007); signal detection performance (Basner et al. 2008) and will as a result, increase the risks of accidents (Barger et al. 2005; Scott et al 2007). Most of the effects such as anxiety are attributed to sleep disturbance as well as other socio-economic factors such as the fear of falling house price etc..

    As for physiological effects, long term exposure to infrasound has been shown to have an effect on certain human cells (I know liver cells have been studied in this context) but it's not been studied extensively that I know of. As for jaw resonance... not sure what that is all about. Your mouth/vocal track has resonance that is responsible for the timbre of your voice and hence your accent, and bone conduction is why your voice sounds slightly different when you record it an hear it played back (most of what you hear of your own voice is 'filtered' somewhat from propagation though your bone structure). Other than this I'm not sure what you could be referring to.

    Anyway for more information of the adverse effects of low frequency noise this article* will prove useful... Although infrasound is not well defined; sounds well below 20Hz are in fact audible at high enough levels but, off the top of my head, this is a level around 90+dB(G) where the G indicates frequency filtering used in infrasound assessments that reflects average audible thresholds (ISO7196, 1995)... although tonality might be lost below about 15/16Hz.... I can safely say you are not producing this level of sound with your jaw alone. Anyway, this paper will tell you a lot about the general study of low frequency noise and it's effects. References for most of the citations above can be found in that paper, if you can't find them and want to know the full reference, or have any follow up questions, let me know.

    * http://westminsterresearch.wmin.ac.uk/4141/1/Benton_2003.pdf
     
    Last edited: Jan 13, 2013
    Elite Jacob likes this.
  6. Pythagorean

    Pythagorean 4,609
    Gold Member

    Re: Search for... something

    Not to mention the wavelength. It's hard to imagine something as small as a human jawbone detecting something so large.
     
  7. Evo

    Staff: Mentor

    Actually, the OP is claiming that the jawbone sends out infrasound. Not the effects of external infrasound on parts of the body.

    His original OP
     
  8. russ_watters

    Staff: Mentor

    C'mon guys: I'm sure the OP meant megahertz, not milihertz (according to my spell checker, no such measure even exists, which isn't surprising). As typos go, not capitalizing the "M" is a pretty minor one here.
     
  9. Evo

    Staff: Mentor

    Yes, the op said infrasound = megahertz, infrasound is below 20 hertz. I believe only one member might have misread it.
     
  10. russ_watters

    Staff: Mentor

    Heh - ok, so it was (probably) the OP's misunderstanding and not a typo....which I then missed. Still, I think correcting that misunderstanding would have worked out better....

    Objects resonate at a frequency determined by mass and elasticity. A bone, being hard, would have a resonant frequency like (probably higher) than a hard piece of wood.
     
    Elite Jacob likes this.
  11. Yeah, obviously even if we know the properties of bone it is difficult to establish a resonant frequency as the Jaw bone is coupled to other parts of the body (the rest of your skull etc) As you probably know, that will affect this, and the material around the bone probably acts as effective damping/absorptive material. So even if your Jaw was resonating at an audible frequency; firstly, it is not doing so of it's own accord, it obviously must be stimulated somehow so it's more likely the noise you hear is due to the initial impulse or noise as opposed to any subsequent resonance, plus if this resonance is audible whether the OP was referring to infra or ultra sound is almost irrelevant; in this context neither of those extremes are likely to be audible.
     
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