In article , Don Pearce
wrote:
On Wed, 27 Sep 2006 10:57:21 +0100, "Keith G"
wrote:



Totally unstressed today - but here we go anyway.

Wooden cones wont dissipate any energy to speak of, whichever way up you
put them.

i became curious about the 'cones and spikes' some years ago. Looked at the
work on vibration in solid structure.

Three things emerged:

1) That with a cone there was no inherent reason for thinking one way up
was different to the other *unless* the materials/surfaces they seperated
have very different acoustic properties. In which case, those surfaces
determine what is going on anyway. (Here 'different' as in 'carpet' versus
'steel' rather the relatively minor differences between most solids
involved.)

2) That the actual shape doesn't matter much unless it caused plastic
deformation of the surfaces it contacts.

3) That oak had acoustic properties surprisingly similar to metals. So
choose oak if you like the look of it.

Oh, and,

4) The cones/spikes tend to transmit vibrations about as well as most
ofther shapes of similar overall size. They are all much smaller than the
wavelengths involved so tend to act as a 'lumped element'.

So if you want isolation/damping, then your deciding to go for squash balls
makes more sense. Oak cones may be prettier, though. :-)

Slainte,

Jim

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