PSN-L Email List Message

Subject: Re: acoustic emissions
From: Charles Patton charles.r.patton@........
Date: Thu, 18 Aug 2011 15:02:34 -0700

I still think that the acoustic emissions would be easily detectable. I 
have piezo film samples (if I can find them!)  and I'll try to mock up a 
test to see what happens.  But in the meantime my thinking runs like this.

If you take one of those micro-pulses, integrate the area and calculate 
using the movement and amount of mass in the instrument it was measured 
on, the answer should be the amount of energy expended in the grain 
relocation.  Then plug that energy into a much narrower pulse and 
multiply times the mass ratio of the pendulum weight to the spring and 
that would be roughly the movement(?) in the spring area due to the 
dislocation.  If you can detect the movement in the pendulum mass with 
capacitance sensing, I should be just as able to see it in the spring as 
that noise floor is just as comparable since piezo film is essentially a 
capacitor also.

Another aspect bothers me.  Earlier in this thread instrument trace were 
shown to compare a stable vs. a non-stable spring.  Subjectively, it 
seemed to me that the amplitude of the "pops" were very similar.  Why 
would that be?  Shouldn't the amplitudes vary in some sort of curve?  
Aren't the grain sizes distributed around a range in the spring?  This 
starts to cut to Brett's question of putting numbers on the phenomenon.  
How about taking the digital samples and plotting the 
distribution/height of the pops?  Should be easier if you have two 
instruments sitting side-by-side so you can easily classify pops from 
external seismo data.

More questions than answers I'm afraid.

Charles R Patton

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