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Thread: Materials that "absorb " sound and vibrations: how do they work?

  1. #1
    Join Date
    Jun 2009

    Materials that "absorb " sound and vibrations: how do they work?

    For materials such as foams that "absorb sound" and rubbery pads that act as vibration dampers, how much of their effect is due to converting the mechanical vibration to heat? - most of the effect? Or is their primary effect to change the frequencies of the vibrations so they are less irritating?

  2. #2
    Join Date
    Oct 2006
    R.I. USA
    One of the successful products employed in sound reduction is a neoprene-lead-neoprene sandwich. Installed on high-end
    marine applications like larger sailboats , we see these panels around the diesel engine compartment . The concept here is
    attenuating sound transmission. When it comes to vibrating, lead is an exceptionally poor vibration component. It works especially well in this application. Makes for a good night's sleep . Nice to have around that Onan generator as well .


  3. #3
    Join Date
    Oct 2009
    a long way away
    Yes, the vibrations are converted to heat.

    And the alternating layers of soft and rigid materials is an old trick. I'm kind of surprised lead is chosen, I thought stiffness rather than mass was the key thing. (I stood my shower pump on several layers of ceramic tile / rubber pond-liner - it is almost silent now.)

  4. #4
    Join Date
    Sep 2003
    I suspect the lead works because any vibrations just plain die because the energy does into non-elastic deformation rather than getting transmitted because the deformations are elastic.
    It's not the mass but rather the malleability that does it.
    Reductionist and proud of it.

    Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
    Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
    A person who won't read has no advantage over one who can't read. Mark Twain

  5. #5
    Join Date
    Jun 2009
    Would a hard material also reflect sound waves from one side in a manner that avoided both transmitting them to the other side and absorbing their energy as heat?

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