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Ear protections, how it works

  1. Nov 16, 2008 #1
    hallo all,

    I was reading some information on my new set of earprotectors and I noticed it said that it is very good against high tones, high frequencies, but not for low ones.

    Why is this? How come you can stop high frequencies more accurate or faster then the low ones with the same material?

    is this simply because low frequencies with long wavelenghts can pass true material easier? or?
  2. jcsd
  3. Nov 16, 2008 #2


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    Science Advisor

    Yes. That is also why when you neighbor is playing very loud rock and roll music late at nght (?*#*?!# him!) you hear, mainly, "boom, boom, boom"!
  4. Nov 16, 2008 #3
    Ah I see, but is there a certain reason or explenation for it?

    Who do low frequencies pass much easier true material then?
  5. Nov 16, 2008 #4


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    Staff: Mentor

    It's a matter of the natural frequency of the objects. Say you have a regular drywall wall. A high frequency sound oscillates too fast to make the wall oscillate, so it gets absorbed. A low frequency sound will make the wall move back and forth, transmitting the sound.
  6. Nov 16, 2008 #5
    Eum, I see

    but why cant they make earprotectors then that stop (absorp) the low frequencies?
    Is this because there are no materials that can be used for this because they are too heavy or to expensive or?

    And is it correct to state that when a material can absorp (stop) the low frequencies it automaticly will also stop high frequencies or not?
  7. Nov 16, 2008 #6


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    Staff: Mentor

    Heavy, yes. In construction, when one wants to stop low frequencies, they use concrete.
    In general, I think so, because things that stop low frequencies have to be pretty thick and heavy and as a result you get both.
  8. Nov 16, 2008 #7
    ok I see.

    thanks a lot.

    However still one question: is there some sort of formula for this or is it just a thing that scientist accept as general knowledge?

    I mean: is there a general formula wich shows that low frequencies are harder to stop then higher one with a certain material X , or its something that is known, but not yet really proven mathematicly?
  9. Nov 17, 2008 #8


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    There's a physiological factor at work as well. Unless the hearing protectors encased your entire head like a space helmet, your skull and jaw bones would still resonate to the sound and channel it to your auditory circuits. That's how bone-conduction 'earphones' work. High frequencies don't have that effect (or, at least, not nearly as pronounced).
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